/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.commons.io;

import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileFilter;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.Reader;
import java.math.BigInteger;
import java.net.URL;
import java.net.URLConnection;
import java.nio.ByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.charset.Charset;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Date;
import java.util.Iterator;
import java.util.List;
import java.util.zip.CRC32;
import java.util.zip.CheckedInputStream;
import java.util.zip.Checksum;

import org.apache.commons.io.filefilter.DirectoryFileFilter;
import org.apache.commons.io.filefilter.FalseFileFilter;
import org.apache.commons.io.filefilter.FileFilterUtils;
import org.apache.commons.io.filefilter.IOFileFilter;
import org.apache.commons.io.filefilter.SuffixFileFilter;
import org.apache.commons.io.filefilter.TrueFileFilter;
import org.apache.commons.io.output.NullOutputStream;

/**
 * General file manipulation utilities.
 * <p>
 * Facilities are provided in the following areas:
 * <ul>
 * <li>writing to a file
 * <li>reading from a file
 * <li>make a directory including parent directories
 * <li>copying files and directories
 * <li>deleting files and directories
 * <li>converting to and from a URL
 * <li>listing files and directories by filter and extension
 * <li>comparing file content
 * <li>file last changed date
 * <li>calculating a checksum
 * </ul>
 * <p>
 * Note that a specific charset should be specified whenever possible.
 * Relying on the platform default means that the code is Locale-dependent.
 * Only use the default if the files are known to always use the platform default.
 * <p>
 * Origin of code: Excalibur, Alexandria, Commons-Utils
 *
 */
public class FileUtils {

    /**
     * Instances should NOT be constructed in standard programming.
     */
    public FileUtils() {
        super();
    }

    /**
     * The number of bytes in a kilobyte.
     */
    public static final long ONE_KB = 1024;

    /**
     * The number of bytes in a kilobyte.
     *
     * @since 2.4
     */
    public static final BigInteger ONE_KB_BI = BigInteger.valueOf(ONE_KB);

    /**
     * The number of bytes in a megabyte.
     */
    public static final long ONE_MB = ONE_KB * ONE_KB;

    /**
     * The number of bytes in a megabyte.
     *
     * @since 2.4
     */
    public static final BigInteger ONE_MB_BI = ONE_KB_BI.multiply(ONE_KB_BI);

    /**
     * The file copy buffer size (30 MB)
     */
    private static final long FILE_COPY_BUFFER_SIZE = ONE_MB * 30;

    /**
     * The number of bytes in a gigabyte.
     */
    public static final long ONE_GB = ONE_KB * ONE_MB;

    /**
     * The number of bytes in a gigabyte.
     *
     * @since 2.4
     */
    public static final BigInteger ONE_GB_BI = ONE_KB_BI.multiply(ONE_MB_BI);

    /**
     * The number of bytes in a terabyte.
     */
    public static final long ONE_TB = ONE_KB * ONE_GB;

    /**
     * The number of bytes in a terabyte.
     *
     * @since 2.4
     */
    public static final BigInteger ONE_TB_BI = ONE_KB_BI.multiply(ONE_GB_BI);

    /**
     * The number of bytes in a petabyte.
     */
    public static final long ONE_PB = ONE_KB * ONE_TB;

    /**
     * The number of bytes in a petabyte.
     *
     * @since 2.4
     */
    public static final BigInteger ONE_PB_BI = ONE_KB_BI.multiply(ONE_TB_BI);

    /**
     * The number of bytes in an exabyte.
     */
    public static final long ONE_EB = ONE_KB * ONE_PB;

    /**
     * The number of bytes in an exabyte.
     *
     * @since 2.4
     */
    public static final BigInteger ONE_EB_BI = ONE_KB_BI.multiply(ONE_PB_BI);

    /**
     * The number of bytes in a zettabyte.
     */
    public static final BigInteger ONE_ZB = BigInteger.valueOf(ONE_KB).multiply(BigInteger.valueOf(ONE_EB));

    /**
     * The number of bytes in a yottabyte.
     */
    public static final BigInteger ONE_YB = ONE_KB_BI.multiply(ONE_ZB);

    /**
     * An empty array of type <code>File</code>.
     */
    public static final File[] EMPTY_FILE_ARRAY = new File[0];

    //-----------------------------------------------------------------------
    /**
     * Construct a file from the set of name elements.
     *
     * @param directory the parent directory
     * @param names the name elements
     * @return the file
     * @since 2.1
     */
    public static File getFile(final File directory, final String... names) {
        if (directory == null) {
            throw new NullPointerException("directory must not be null");
        }
        if (names == null) {
            throw new NullPointerException("names must not be null");
        }
        File file = directory;
        for (final String name : names) {
            file = new File(file, name);
        }
        return file;
    }

    /**
     * Construct a file from the set of name elements.
     *
     * @param names the name elements
     * @return the file
     * @since 2.1
     */
    public static File getFile(final String... names) {
        if (names == null) {
            throw new NullPointerException("names must not be null");
        }
        File file = null;
        for (final String name : names) {
            if (file == null) {
                file = new File(name);
            } else {
                file = new File(file, name);
            }
        }
        return file;
    }

    /**
     * Returns the path to the system temporary directory.
     *
     * @return the path to the system temporary directory.
     *
     * @since 2.0
     */
    public static String getTempDirectoryPath() {
        return System.getProperty("java.io.tmpdir");
    }

    /**
     * Returns a {@link File} representing the system temporary directory.
     *
     * @return the system temporary directory.
     *
     * @since 2.0
     */
    public static File getTempDirectory() {
        return new File(getTempDirectoryPath());
    }

    /**
     * Returns the path to the user's home directory.
     *
     * @return the path to the user's home directory.
     *
     * @since 2.0
     */
    public static String getUserDirectoryPath() {
        return System.getProperty("user.home");
    }

    /**
     * Returns a {@link File} representing the user's home directory.
     *
     * @return the user's home directory.
     *
     * @since 2.0
     */
    public static File getUserDirectory() {
        return new File(getUserDirectoryPath());
    }

    //-----------------------------------------------------------------------
    /**
     * Opens a {@link FileInputStream} for the specified file, providing better
     * error messages than simply calling <code>new FileInputStream(file)</code>.
     * <p>
     * At the end of the method either the stream will be successfully opened,
     * or an exception will have been thrown.
     * <p>
     * An exception is thrown if the file does not exist.
     * An exception is thrown if the file object exists but is a directory.
     * An exception is thrown if the file exists but cannot be read.
     *
     * @param file the file to open for input, must not be {@code null}
     * @return a new {@link FileInputStream} for the specified file
     * @throws FileNotFoundException if the file does not exist
     * @throws IOException           if the file object is a directory
     * @throws IOException           if the file cannot be read
     * @since 1.3
     */
    public static FileInputStream openInputStream(final File file) throws IOException {
        if (file.exists()) {
            if (file.isDirectory()) {
                throw new IOException("File '" + file + "' exists but is a directory");
            }
            if (file.canRead() == false) {
                throw new IOException("File '" + file + "' cannot be read");
            }
        } else {
            throw new FileNotFoundException("File '" + file + "' does not exist");
        }
        return new FileInputStream(file);
    }

    //-----------------------------------------------------------------------
    /**
     * Opens a {@link FileOutputStream} for the specified file, checking and
     * creating the parent directory if it does not exist.
     * <p>
     * At the end of the method either the stream will be successfully opened,
     * or an exception will have been thrown.
     * <p>
     * The parent directory will be created if it does not exist.
     * The file will be created if it does not exist.
     * An exception is thrown if the file object exists but is a directory.
     * An exception is thrown if the file exists but cannot be written to.
     * An exception is thrown if the parent directory cannot be created.
     *
     * @param file the file to open for output, must not be {@code null}
     * @return a new {@link FileOutputStream} for the specified file
     * @throws IOException if the file object is a directory
     * @throws IOException if the file cannot be written to
     * @throws IOException if a parent directory needs creating but that fails
     * @since 1.3
     */
    public static FileOutputStream openOutputStream(final File file) throws IOException {
        return openOutputStream(file, false);
    }

    /**
     * Opens a {@link FileOutputStream} for the specified file, checking and
     * creating the parent directory if it does not exist.
     * <p>
     * At the end of the method either the stream will be successfully opened,
     * or an exception will have been thrown.
     * <p>
     * The parent directory will be created if it does not exist.
     * The file will be created if it does not exist.
     * An exception is thrown if the file object exists but is a directory.
     * An exception is thrown if the file exists but cannot be written to.
     * An exception is thrown if the parent directory cannot be created.
     *
     * @param file   the file to open for output, must not be {@code null}
     * @param append if {@code true}, then bytes will be added to the
     *               end of the file rather than overwriting
     * @return a new {@link FileOutputStream} for the specified file
     * @throws IOException if the file object is a directory
     * @throws IOException if the file cannot be written to
     * @throws IOException if a parent directory needs creating but that fails
     * @since 2.1
     */
    public static FileOutputStream openOutputStream(final File file, final boolean append) throws IOException {
        if (file.exists()) {
            if (file.isDirectory()) {
                throw new IOException("File '" + file + "' exists but is a directory");
            }
            if (file.canWrite() == false) {
                throw new IOException("File '" + file + "' cannot be written to");
            }
        } else {
            final File parent = file.getParentFile();
            if (parent != null) {
                if (!parent.mkdirs() && !parent.isDirectory()) {
                    throw new IOException("Directory '" + parent + "' could not be created");
                }
            }
        }
        return new FileOutputStream(file, append);
    }

    //-----------------------------------------------------------------------
    /**
     * Returns a human-readable version of the file size, where the input represents a specific number of bytes.
     * <p>
     * If the size is over 1GB, the size is returned as the number of whole GB, i.e. the size is rounded down to the
     * nearest GB boundary.
     * </p>
     * <p>
     * Similarly for the 1MB and 1KB boundaries.
     * </p>
     *
     * @param size the number of bytes
     * @return a human-readable display value (includes units - EB, PB, TB, GB, MB, KB or bytes)
     * @see <a href="https://issues.apache.org/jira/browse/IO-226">IO-226 - should the rounding be changed?</a>
     * @since 2.4
     */
    // See https://issues.apache.org/jira/browse/IO-226 - should the rounding be changed?
    public static String byteCountToDisplaySize(final BigInteger size) {
        String displaySize;

        if (size.divide(ONE_EB_BI).compareTo(BigInteger.ZERO) > 0) {
            displaySize = String.valueOf(size.divide(ONE_EB_BI)) + " EB";
        } else if (size.divide(ONE_PB_BI).compareTo(BigInteger.ZERO) > 0) {
            displaySize = String.valueOf(size.divide(ONE_PB_BI)) + " PB";
        } else if (size.divide(ONE_TB_BI).compareTo(BigInteger.ZERO) > 0) {
            displaySize = String.valueOf(size.divide(ONE_TB_BI)) + " TB";
        } else if (size.divide(ONE_GB_BI).compareTo(BigInteger.ZERO) > 0) {
            displaySize = String.valueOf(size.divide(ONE_GB_BI)) + " GB";
        } else if (size.divide(ONE_MB_BI).compareTo(BigInteger.ZERO) > 0) {
            displaySize = String.valueOf(size.divide(ONE_MB_BI)) + " MB";
        } else if (size.divide(ONE_KB_BI).compareTo(BigInteger.ZERO) > 0) {
            displaySize = String.valueOf(size.divide(ONE_KB_BI)) + " KB";
        } else {
            displaySize = String.valueOf(size) + " bytes";
        }
        return displaySize;
    }

    /**
     * Returns a human-readable version of the file size, where the input represents a specific number of bytes.
     * <p>
     * If the size is over 1GB, the size is returned as the number of whole GB, i.e. the size is rounded down to the
     * nearest GB boundary.
     * </p>
     * <p>
     * Similarly for the 1MB and 1KB boundaries.
     * </p>
     *
     * @param size the number of bytes
     * @return a human-readable display value (includes units - EB, PB, TB, GB, MB, KB or bytes)
     * @see <a href="https://issues.apache.org/jira/browse/IO-226">IO-226 - should the rounding be changed?</a>
     */
    // See https://issues.apache.org/jira/browse/IO-226 - should the rounding be changed?
    public static String byteCountToDisplaySize(final long size) {
        return byteCountToDisplaySize(BigInteger.valueOf(size));
    }

    //-----------------------------------------------------------------------
    /**
     * Implements the same behaviour as the "touch" utility on Unix. It creates
     * a new file with size 0 or, if the file exists already, it is opened and
     * closed without modifying it, but updating the file date and time.
     * <p>
     * NOTE: As from v1.3, this method throws an IOException if the last
     * modified date of the file cannot be set. Also, as from v1.3 this method
     * creates parent directories if they do not exist.
     *
     * @param file the File to touch
     * @throws IOException If an I/O problem occurs
     */
    public static void touch(final File file) throws IOException {
        if (!file.exists()) {
            openOutputStream(file).close();
        }
        final boolean success = file.setLastModified(System.currentTimeMillis());
        if (!success) {
            throw new IOException("Unable to set the last modification time for " + file);
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Converts a Collection containing java.io.File instanced into array
     * representation. This is to account for the difference between
     * File.listFiles() and FileUtils.listFiles().
     *
     * @param files a Collection containing java.io.File instances
     * @return an array of java.io.File
     */
    public static File[] convertFileCollectionToFileArray(final Collection<File> files) {
        return files.toArray(new File[files.size()]);
    }

    //-----------------------------------------------------------------------
    /**
     * Finds files within a given directory (and optionally its
     * subdirectories). All files found are filtered by an IOFileFilter.
     *
     * @param files                 the collection of files found.
     * @param directory             the directory to search in.
     * @param filter                the filter to apply to files and directories.
     * @param includeSubDirectories indicates if will include the subdirectories themselves
     */
    private static void innerListFiles(final Collection<File> files, final File directory,
                                       final IOFileFilter filter, final boolean includeSubDirectories) {
        final File[] found = directory.listFiles((FileFilter) filter);

        if (found != null) {
            for (final File file : found) {
                if (file.isDirectory()) {
                    if (includeSubDirectories) {
                        files.add(file);
                    }
                    innerListFiles(files, file, filter, includeSubDirectories);
                } else {
                    files.add(file);
                }
            }
        }
    }

    /**
     * Finds files within a given directory (and optionally its
     * subdirectories). All files found are filtered by an IOFileFilter.
     * <p>
     * If your search should recurse into subdirectories you can pass in
     * an IOFileFilter for directories. You don't need to bind a
     * DirectoryFileFilter (via logical AND) to this filter. This method does
     * that for you.
     * <p>
     * An example: If you want to search through all directories called
     * "temp" you pass in <code>FileFilterUtils.NameFileFilter("temp")</code>
     * <p>
     * Another common usage of this method is find files in a directory
     * tree but ignoring the directories generated CVS. You can simply pass
     * in <code>FileFilterUtils.makeCVSAware(null)</code>.
     *
     * @param directory  the directory to search in
     * @param fileFilter filter to apply when finding files. Must not be {@code null},
     *                   use {@link TrueFileFilter#INSTANCE} to match all files in selected directories.
     * @param dirFilter  optional filter to apply when finding subdirectories.
     *                   If this parameter is {@code null}, subdirectories will not be included in the
     *                   search. Use {@link TrueFileFilter#INSTANCE} to match all directories.
     * @return a collection of java.io.File with the matching files
     * @see FileFilterUtils
     * @see org.apache.commons.io.filefilter.NameFileFilter
     */
    public static Collection<File> listFiles(
            final File directory, final IOFileFilter fileFilter, final IOFileFilter dirFilter) {
        validateListFilesParameters(directory, fileFilter);

        final IOFileFilter effFileFilter = setUpEffectiveFileFilter(fileFilter);
        final IOFileFilter effDirFilter = setUpEffectiveDirFilter(dirFilter);

        //Find files
        final Collection<File> files = new java.util.LinkedList<>();
        innerListFiles(files, directory,
                FileFilterUtils.or(effFileFilter, effDirFilter), false);
        return files;
    }

    /**
     * Validates the given arguments.
     * <ul>
     * <li>Throws {@link IllegalArgumentException} if {@code directory} is not a directory</li>
     * <li>Throws {@link NullPointerException} if {@code fileFilter} is null</li>
     * </ul>
     *
     * @param directory  The File to test
     * @param fileFilter The IOFileFilter to test
     */
    private static void validateListFilesParameters(final File directory, final IOFileFilter fileFilter) {
        if (!directory.isDirectory()) {
            throw new IllegalArgumentException("Parameter 'directory' is not a directory: " + directory);
        }
        if (fileFilter == null) {
            throw new NullPointerException("Parameter 'fileFilter' is null");
        }
    }

    /**
     * Returns a filter that accepts files in addition to the {@link File} objects accepted by the given filter.
     *
     * @param fileFilter a base filter to add to
     * @return a filter that accepts files
     */
    private static IOFileFilter setUpEffectiveFileFilter(final IOFileFilter fileFilter) {
        return FileFilterUtils.and(fileFilter, FileFilterUtils.notFileFilter(DirectoryFileFilter.INSTANCE));
    }

    /**
     * Returns a filter that accepts directories in addition to the {@link File} objects accepted by the given filter.
     *
     * @param dirFilter a base filter to add to
     * @return a filter that accepts directories
     */
    private static IOFileFilter setUpEffectiveDirFilter(final IOFileFilter dirFilter) {
        return dirFilter == null ? FalseFileFilter.INSTANCE : FileFilterUtils.and(dirFilter,
                DirectoryFileFilter.INSTANCE);
    }

    /**
     * Finds files within a given directory (and optionally its
     * subdirectories). All files found are filtered by an IOFileFilter.
     * <p>
     * The resulting collection includes the starting directory and
     * any subdirectories that match the directory filter.
     * <p>
     *
     * @param directory  the directory to search in
     * @param fileFilter filter to apply when finding files.
     * @param dirFilter  optional filter to apply when finding subdirectories.
     *                   If this parameter is {@code null}, subdirectories will not be included in the
     *                   search. Use TrueFileFilter.INSTANCE to match all directories.
     * @return a collection of java.io.File with the matching files
     * @see FileUtils#listFiles
     * @see FileFilterUtils
     * @see org.apache.commons.io.filefilter.NameFileFilter
     * @since 2.2
     */
    public static Collection<File> listFilesAndDirs(
            final File directory, final IOFileFilter fileFilter, final IOFileFilter dirFilter) {
        validateListFilesParameters(directory, fileFilter);

        final IOFileFilter effFileFilter = setUpEffectiveFileFilter(fileFilter);
        final IOFileFilter effDirFilter = setUpEffectiveDirFilter(dirFilter);

        //Find files
        final Collection<File> files = new java.util.LinkedList<>();
        if (directory.isDirectory()) {
            files.add(directory);
        }
        innerListFiles(files, directory,
                FileFilterUtils.or(effFileFilter, effDirFilter), true);
        return files;
    }

    /**
     * Allows iteration over the files in given directory (and optionally
     * its subdirectories).
     * <p>
     * All files found are filtered by an IOFileFilter. This method is
     * based on {@link #listFiles(File, IOFileFilter, IOFileFilter)},
     * which supports Iterable ('foreach' loop).
     * <p>
     * @param directory  the directory to search in
     * @param fileFilter filter to apply when finding files.
     * @param dirFilter  optional filter to apply when finding subdirectories.
     *                   If this parameter is {@code null}, subdirectories will not be included in the
     *                   search. Use TrueFileFilter.INSTANCE to match all directories.
     * @return an iterator of java.io.File for the matching files
     * @see FileFilterUtils
     * @see org.apache.commons.io.filefilter.NameFileFilter
     * @since 1.2
     */
    public static Iterator<File> iterateFiles(
            final File directory, final IOFileFilter fileFilter, final IOFileFilter dirFilter) {
        return listFiles(directory, fileFilter, dirFilter).iterator();
    }

    /**
     * Allows iteration over the files in given directory (and optionally
     * its subdirectories).
     * <p>
     * All files found are filtered by an IOFileFilter. This method is
     * based on {@link #listFilesAndDirs(File, IOFileFilter, IOFileFilter)},
     * which supports Iterable ('foreach' loop).
     * <p>
     * The resulting iterator includes the subdirectories themselves.
     *
     * @param directory  the directory to search in
     * @param fileFilter filter to apply when finding files.
     * @param dirFilter  optional filter to apply when finding subdirectories.
     *                   If this parameter is {@code null}, subdirectories will not be included in the
     *                   search. Use TrueFileFilter.INSTANCE to match all directories.
     * @return an iterator of java.io.File for the matching files
     * @see FileFilterUtils
     * @see org.apache.commons.io.filefilter.NameFileFilter
     * @since 2.2
     */
    public static Iterator<File> iterateFilesAndDirs(final File directory, final IOFileFilter fileFilter,
                                                     final IOFileFilter dirFilter) {
        return listFilesAndDirs(directory, fileFilter, dirFilter).iterator();
    }

    //-----------------------------------------------------------------------
    /**
     * Converts an array of file extensions to suffixes for use
     * with IOFileFilters.
     *
     * @param extensions an array of extensions. Format: {"java", "xml"}
     * @return an array of suffixes. Format: {".java", ".xml"}
     */
    private static String[] toSuffixes(final String[] extensions) {
        final String[] suffixes = new String[extensions.length];
        for (int i = 0; i < extensions.length; i++) {
            suffixes[i] = "." + extensions[i];
        }
        return suffixes;
    }


    /**
     * Finds files within a given directory (and optionally its subdirectories)
     * which match an array of extensions.
     *
     * @param directory  the directory to search in
     * @param extensions an array of extensions, ex. {"java","xml"}. If this
     *                   parameter is {@code null}, all files are returned.
     * @param recursive  if true all subdirectories are searched as well
     * @return a collection of java.io.File with the matching files
     */
    public static Collection<File> listFiles(
            final File directory, final String[] extensions, final boolean recursive) {
        IOFileFilter filter;
        if (extensions == null) {
            filter = TrueFileFilter.INSTANCE;
        } else {
            final String[] suffixes = toSuffixes(extensions);
            filter = new SuffixFileFilter(suffixes);
        }
        return listFiles(directory, filter,
                recursive ? TrueFileFilter.INSTANCE : FalseFileFilter.INSTANCE);
    }

    /**
     * Allows iteration over the files in a given directory (and optionally
     * its subdirectories) which match an array of extensions. This method
     * is based on {@link #listFiles(File, String[], boolean)},
     * which supports Iterable ('foreach' loop).
     *
     * @param directory  the directory to search in
     * @param extensions an array of extensions, ex. {"java","xml"}. If this
     *                   parameter is {@code null}, all files are returned.
     * @param recursive  if true all subdirectories are searched as well
     * @return an iterator of java.io.File with the matching files
     * @since 1.2
     */
    public static Iterator<File> iterateFiles(
            final File directory, final String[] extensions, final boolean recursive) {
        return listFiles(directory, extensions, recursive).iterator();
    }

    //-----------------------------------------------------------------------
    /**
     * Compares the contents of two files to determine if they are equal or not.
     * <p>
     * This method checks to see if the two files are different lengths
     * or if they point to the same file, before resorting to byte-by-byte
     * comparison of the contents.
     * <p>
     * Code origin: Avalon
     *
     * @param file1 the first file
     * @param file2 the second file
     * @return true if the content of the files are equal or they both don't
     * exist, false otherwise
     * @throws IOException in case of an I/O error
     */
    public static boolean contentEquals(final File file1, final File file2) throws IOException {
        final boolean file1Exists = file1.exists();
        if (file1Exists != file2.exists()) {
            return false;
        }

        if (!file1Exists) {
            // two not existing files are equal
            return true;
        }

        if (file1.isDirectory() || file2.isDirectory()) {
            // don't want to compare directory contents
            throw new IOException("Can't compare directories, only files");
        }

        if (file1.length() != file2.length()) {
            // lengths differ, cannot be equal
            return false;
        }

        if (file1.getCanonicalFile().equals(file2.getCanonicalFile())) {
            // same file
            return true;
        }

        try (InputStream input1 = new FileInputStream(file1);
             InputStream input2 = new FileInputStream(file2)) {
            return IOUtils.contentEquals(input1, input2);
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Compares the contents of two files to determine if they are equal or not.
     * <p>
     * This method checks to see if the two files point to the same file,
     * before resorting to line-by-line comparison of the contents.
     * <p>
     *
     * @param file1       the first file
     * @param file2       the second file
     * @param charsetName the character encoding to be used.
     *                    May be null, in which case the platform default is used
     * @return true if the content of the files are equal or neither exists,
     * false otherwise
     * @throws IOException in case of an I/O error
     * @see IOUtils#contentEqualsIgnoreEOL(Reader, Reader)
     * @since 2.2
     */
    public static boolean contentEqualsIgnoreEOL(final File file1, final File file2, final String charsetName)
            throws IOException {
        final boolean file1Exists = file1.exists();
        if (file1Exists != file2.exists()) {
            return false;
        }

        if (!file1Exists) {
            // two not existing files are equal
            return true;
        }

        if (file1.isDirectory() || file2.isDirectory()) {
            // don't want to compare directory contents
            throw new IOException("Can't compare directories, only files");
        }

        if (file1.getCanonicalFile().equals(file2.getCanonicalFile())) {
            // same file
            return true;
        }

        try (Reader input1 = charsetName == null
                                 ? new InputStreamReader(new FileInputStream(file1), Charset.defaultCharset())
                                 : new InputStreamReader(new FileInputStream(file1), charsetName);
             Reader input2 = charsetName == null
                                 ? new InputStreamReader(new FileInputStream(file2), Charset.defaultCharset())
                                 : new InputStreamReader(new FileInputStream(file2), charsetName)) {
            return IOUtils.contentEqualsIgnoreEOL(input1, input2);
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Convert from a <code>URL</code> to a <code>File</code>.
     * <p>
     * From version 1.1 this method will decode the URL.
     * Syntax such as <code>file:///my%20docs/file.txt</code> will be
     * correctly decoded to <code>/my docs/file.txt</code>. Starting with version
     * 1.5, this method uses UTF-8 to decode percent-encoded octets to characters.
     * Additionally, malformed percent-encoded octets are handled leniently by
     * passing them through literally.
     *
     * @param url the file URL to convert, {@code null} returns {@code null}
     * @return the equivalent <code>File</code> object, or {@code null}
     * if the URL's protocol is not <code>file</code>
     */
    public static File toFile(final URL url) {
        if (url == null || !"file".equalsIgnoreCase(url.getProtocol())) {
            return null;
        } else {
            String filename = url.getFile().replace('/', File.separatorChar);
            filename = decodeUrl(filename);
            return new File(filename);
        }
    }

    /**
     * Decodes the specified URL as per RFC 3986, i.e. transforms
     * percent-encoded octets to characters by decoding with the UTF-8 character
     * set. This function is primarily intended for usage with
     * {@link URL} which unfortunately does not enforce proper URLs. As
     * such, this method will leniently accept invalid characters or malformed
     * percent-encoded octets and simply pass them literally through to the
     * result string. Except for rare edge cases, this will make unencoded URLs
     * pass through unaltered.
     *
     * @param url The URL to decode, may be {@code null}.
     * @return The decoded URL or {@code null} if the input was
     * {@code null}.
     */
    static String decodeUrl(final String url) {
        String decoded = url;
        if (url != null && url.indexOf('%') >= 0) {
            final int n = url.length();
            final StringBuilder buffer = new StringBuilder();
            final ByteBuffer bytes = ByteBuffer.allocate(n);
            for (int i = 0; i < n; ) {
                if (url.charAt(i) == '%') {
                    try {
                        do {
                            final byte octet = (byte) Integer.parseInt(url.substring(i + 1, i + 3), 16);
                            bytes.put(octet);
                            i += 3;
                        } while (i < n && url.charAt(i) == '%');
                        continue;
                    } catch (final RuntimeException e) {
                        // malformed percent-encoded octet, fall through and
                        // append characters literally
                    } finally {
                        if (bytes.position() > 0) {
                            bytes.flip();
                            buffer.append(StandardCharsets.UTF_8.decode(bytes).toString());
                            bytes.clear();
                        }
                    }
                }
                buffer.append(url.charAt(i++));
            }
            decoded = buffer.toString();
        }
        return decoded;
    }

    /**
     * Converts each of an array of <code>URL</code> to a <code>File</code>.
     * <p>
     * Returns an array of the same size as the input.
     * If the input is {@code null}, an empty array is returned.
     * If the input contains {@code null}, the output array contains {@code null} at the same
     * index.
     * <p>
     * This method will decode the URL.
     * Syntax such as <code>file:///my%20docs/file.txt</code> will be
     * correctly decoded to <code>/my docs/file.txt</code>.
     *
     * @param urls the file URLs to convert, {@code null} returns empty array
     * @return a non-{@code null} array of Files matching the input, with a {@code null} item
     * if there was a {@code null} at that index in the input array
     * @throws IllegalArgumentException if any file is not a URL file
     * @throws IllegalArgumentException if any file is incorrectly encoded
     * @since 1.1
     */
    public static File[] toFiles(final URL[] urls) {
        if (urls == null || urls.length == 0) {
            return EMPTY_FILE_ARRAY;
        }
        final File[] files = new File[urls.length];
        for (int i = 0; i < urls.length; i++) {
            final URL url = urls[i];
            if (url != null) {
                if (url.getProtocol().equals("file") == false) {
                    throw new IllegalArgumentException(
                            "URL could not be converted to a File: " + url);
                }
                files[i] = toFile(url);
            }
        }
        return files;
    }

    /**
     * Converts each of an array of <code>File</code> to a <code>URL</code>.
     * <p>
     * Returns an array of the same size as the input.
     *
     * @param files the files to convert, must not be {@code null}
     * @return an array of URLs matching the input
     * @throws IOException          if a file cannot be converted
     * @throws NullPointerException if the parameter is null
     */
    public static URL[] toURLs(final File[] files) throws IOException {
        final URL[] urls = new URL[files.length];

        for (int i = 0; i < urls.length; i++) {
            urls[i] = files[i].toURI().toURL();
        }

        return urls;
    }

    //-----------------------------------------------------------------------
    /**
     * Copies a file to a directory preserving the file date.
     * <p>
     * This method copies the contents of the specified source file
     * to a file of the same name in the specified destination directory.
     * The destination directory is created if it does not exist.
     * If the destination file exists, then this method will overwrite it.
     * <p>
     * <strong>Note:</strong> This method tries to preserve the file's last
     * modified date/times using {@link File#setLastModified(long)}, however
     * it is not guaranteed that the operation will succeed.
     * If the modification operation fails, no indication is provided.
     *
     * @param srcFile an existing file to copy, must not be {@code null}
     * @param destDir the directory to place the copy in, must not be {@code null}
     *
     * @throws NullPointerException if source or destination is null
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs during copying
     * @see #copyFile(File, File, boolean)
     */
    public static void copyFileToDirectory(final File srcFile, final File destDir) throws IOException {
        copyFileToDirectory(srcFile, destDir, true);
    }

    /**
     * Copies a file to a directory optionally preserving the file date.
     * <p>
     * This method copies the contents of the specified source file
     * to a file of the same name in the specified destination directory.
     * The destination directory is created if it does not exist.
     * If the destination file exists, then this method will overwrite it.
     * <p>
     * <strong>Note:</strong> Setting <code>preserveFileDate</code> to
     * {@code true} tries to preserve the file's last modified
     * date/times using {@link File#setLastModified(long)}, however it is
     * not guaranteed that the operation will succeed.
     * If the modification operation fails, no indication is provided.
     *
     * @param srcFile          an existing file to copy, must not be {@code null}
     * @param destDir          the directory to place the copy in, must not be {@code null}
     * @param preserveFileDate true if the file date of the copy
     *                         should be the same as the original
     *
     * @throws NullPointerException if source or destination is {@code null}
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs during copying
     * @throws IOException          if the output file length is not the same as the input file length after the copy
     * completes
     * @see #copyFile(File, File, boolean)
     * @since 1.3
     */
    public static void copyFileToDirectory(final File srcFile, final File destDir, final boolean preserveFileDate)
            throws IOException {
        if (destDir == null) {
            throw new NullPointerException("Destination must not be null");
        }
        if (destDir.exists() && destDir.isDirectory() == false) {
            throw new IllegalArgumentException("Destination '" + destDir + "' is not a directory");
        }
        final File destFile = new File(destDir, srcFile.getName());
        copyFile(srcFile, destFile, preserveFileDate);
    }

    /**
     * Copies a file to a new location preserving the file date.
     * <p>
     * This method copies the contents of the specified source file to the
     * specified destination file. The directory holding the destination file is
     * created if it does not exist. If the destination file exists, then this
     * method will overwrite it.
     * <p>
     * <strong>Note:</strong> This method tries to preserve the file's last
     * modified date/times using {@link File#setLastModified(long)}, however
     * it is not guaranteed that the operation will succeed.
     * If the modification operation fails, no indication is provided.
     *
     * @param srcFile  an existing file to copy, must not be {@code null}
     * @param destFile the new file, must not be {@code null}
     *
     * @throws NullPointerException if source or destination is {@code null}
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs during copying
     * @throws IOException          if the output file length is not the same as the input file length after the copy
     * completes
     * @see #copyFileToDirectory(File, File)
     * @see #copyFile(File, File, boolean)
     */
    public static void copyFile(final File srcFile, final File destFile) throws IOException {
        copyFile(srcFile, destFile, true);
    }

    /**
     * Copies a file to a new location.
     * <p>
     * This method copies the contents of the specified source file
     * to the specified destination file.
     * The directory holding the destination file is created if it does not exist.
     * If the destination file exists, then this method will overwrite it.
     * <p>
     * <strong>Note:</strong> Setting <code>preserveFileDate</code> to
     * {@code true} tries to preserve the file's last modified
     * date/times using {@link File#setLastModified(long)}, however it is
     * not guaranteed that the operation will succeed.
     * If the modification operation fails, no indication is provided.
     *
     * @param srcFile          an existing file to copy, must not be {@code null}
     * @param destFile         the new file, must not be {@code null}
     * @param preserveFileDate true if the file date of the copy
     *                         should be the same as the original
     *
     * @throws NullPointerException if source or destination is {@code null}
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs during copying
     * @throws IOException          if the output file length is not the same as the input file length after the copy
     * completes
     * @see #copyFileToDirectory(File, File, boolean)
     * @see #doCopyFile(File, File, boolean)
     */
    public static void copyFile(final File srcFile, final File destFile,
                                final boolean preserveFileDate) throws IOException {
        checkFileRequirements(srcFile, destFile);
        if (srcFile.isDirectory()) {
            throw new IOException("Source '" + srcFile + "' exists but is a directory");
        }
        if (srcFile.getCanonicalPath().equals(destFile.getCanonicalPath())) {
            throw new IOException("Source '" + srcFile + "' and destination '" + destFile + "' are the same");
        }
        final File parentFile = destFile.getParentFile();
        if (parentFile != null) {
            if (!parentFile.mkdirs() && !parentFile.isDirectory()) {
                throw new IOException("Destination '" + parentFile + "' directory cannot be created");
            }
        }
        if (destFile.exists() && destFile.canWrite() == false) {
            throw new IOException("Destination '" + destFile + "' exists but is read-only");
        }
        doCopyFile(srcFile, destFile, preserveFileDate);
    }

    /**
     * Copy bytes from a <code>File</code> to an <code>OutputStream</code>.
     * <p>
     * This method buffers the input internally, so there is no need to use a <code>BufferedInputStream</code>.
     * </p>
     *
     * @param input  the <code>File</code> to read from
     * @param output the <code>OutputStream</code> to write to
     * @return the number of bytes copied
     * @throws NullPointerException if the input or output is null
     * @throws IOException          if an I/O error occurs
     * @since 2.1
     */
    public static long copyFile(final File input, final OutputStream output) throws IOException {
        try (FileInputStream fis = new FileInputStream(input)) {
            return IOUtils.copyLarge(fis, output);
        }
    }

    /**
     * Internal copy file method.
     * This caches the original file length, and throws an IOException
     * if the output file length is different from the current input file length.
     * So it may fail if the file changes size.
     * It may also fail with "IllegalArgumentException: Negative size" if the input file is truncated part way
     * through copying the data and the new file size is less than the current position.
     *
     * @param srcFile          the validated source file, must not be {@code null}
     * @param destFile         the validated destination file, must not be {@code null}
     * @param preserveFileDate whether to preserve the file date
     * @throws IOException              if an error occurs
     * @throws IOException              if the output file length is not the same as the input file length after the
     * copy completes
     * @throws IllegalArgumentException "Negative size" if the file is truncated so that the size is less than the
     * position
     */
    private static void doCopyFile(final File srcFile, final File destFile, final boolean preserveFileDate)
            throws IOException {
        if (destFile.exists() && destFile.isDirectory()) {
            throw new IOException("Destination '" + destFile + "' exists but is a directory");
        }

        try (FileInputStream fis = new FileInputStream(srcFile);
             FileChannel input = fis.getChannel();
             FileOutputStream fos = new FileOutputStream(destFile);
             FileChannel output = fos.getChannel()) {
            final long size = input.size(); // TODO See IO-386
            long pos = 0;
            long count = 0;
            while (pos < size) {
                final long remain = size - pos;
                count = remain > FILE_COPY_BUFFER_SIZE ? FILE_COPY_BUFFER_SIZE : remain;
                final long bytesCopied = output.transferFrom(input, pos, count);
                if (bytesCopied == 0) { // IO-385 - can happen if file is truncated after caching the size
                    break; // ensure we don't loop forever
                }
                pos += bytesCopied;
            }
        }

        final long srcLen = srcFile.length(); // TODO See IO-386
        final long dstLen = destFile.length(); // TODO See IO-386
        if (srcLen != dstLen) {
            throw new IOException("Failed to copy full contents from '" +
                    srcFile + "' to '" + destFile + "' Expected length: " + srcLen + " Actual: " + dstLen);
        }
        if (preserveFileDate) {
            destFile.setLastModified(srcFile.lastModified());
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Copies a directory to within another directory preserving the file dates.
     * <p>
     * This method copies the source directory and all its contents to a
     * directory of the same name in the specified destination directory.
     * <p>
     * The destination directory is created if it does not exist.
     * If the destination directory did exist, then this method merges
     * the source with the destination, with the source taking precedence.
     * <p>
     * <strong>Note:</strong> This method tries to preserve the files' last
     * modified date/times using {@link File#setLastModified(long)}, however
     * it is not guaranteed that those operations will succeed.
     * If the modification operation fails, no indication is provided.
     *
     * @param srcDir  an existing directory to copy, must not be {@code null}
     * @param destDir the directory to place the copy in, must not be {@code null}
     *
     * @throws NullPointerException if source or destination is {@code null}
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs during copying
     * @since 1.2
     */
    public static void copyDirectoryToDirectory(final File srcDir, final File destDir) throws IOException {
        if (srcDir == null) {
            throw new NullPointerException("Source must not be null");
        }
        if (srcDir.exists() && srcDir.isDirectory() == false) {
            throw new IllegalArgumentException("Source '" + destDir + "' is not a directory");
        }
        if (destDir == null) {
            throw new NullPointerException("Destination must not be null");
        }
        if (destDir.exists() && destDir.isDirectory() == false) {
            throw new IllegalArgumentException("Destination '" + destDir + "' is not a directory");
        }
        copyDirectory(srcDir, new File(destDir, srcDir.getName()), true);
    }

    /**
     * Copies a whole directory to a new location preserving the file dates.
     * <p>
     * This method copies the specified directory and all its child
     * directories and files to the specified destination.
     * The destination is the new location and name of the directory.
     * <p>
     * The destination directory is created if it does not exist.
     * If the destination directory did exist, then this method merges
     * the source with the destination, with the source taking precedence.
     * <p>
     * <strong>Note:</strong> This method tries to preserve the files' last
     * modified date/times using {@link File#setLastModified(long)}, however
     * it is not guaranteed that those operations will succeed.
     * If the modification operation fails, no indication is provided.
     *
     * @param srcDir  an existing directory to copy, must not be {@code null}
     * @param destDir the new directory, must not be {@code null}
     *
     * @throws NullPointerException if source or destination is {@code null}
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs during copying
     * @since 1.1
     */
    public static void copyDirectory(final File srcDir, final File destDir) throws IOException {
        copyDirectory(srcDir, destDir, true);
    }

    /**
     * Copies a whole directory to a new location.
     * <p>
     * This method copies the contents of the specified source directory
     * to within the specified destination directory.
     * <p>
     * The destination directory is created if it does not exist.
     * If the destination directory did exist, then this method merges
     * the source with the destination, with the source taking precedence.
     * <p>
     * <strong>Note:</strong> Setting <code>preserveFileDate</code> to
     * {@code true} tries to preserve the files' last modified
     * date/times using {@link File#setLastModified(long)}, however it is
     * not guaranteed that those operations will succeed.
     * If the modification operation fails, no indication is provided.
     *
     * @param srcDir           an existing directory to copy, must not be {@code null}
     * @param destDir          the new directory, must not be {@code null}
     * @param preserveFileDate true if the file date of the copy
     *                         should be the same as the original
     *
     * @throws NullPointerException if source or destination is {@code null}
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs during copying
     * @since 1.1
     */
    public static void copyDirectory(final File srcDir, final File destDir,
                                     final boolean preserveFileDate) throws IOException {
        copyDirectory(srcDir, destDir, null, preserveFileDate);
    }

    /**
     * Copies a filtered directory to a new location preserving the file dates.
     * <p>
     * This method copies the contents of the specified source directory
     * to within the specified destination directory.
     * <p>
     * The destination directory is created if it does not exist.
     * If the destination directory did exist, then this method merges
     * the source with the destination, with the source taking precedence.
     * <p>
     * <strong>Note:</strong> This method tries to preserve the files' last
     * modified date/times using {@link File#setLastModified(long)}, however
     * it is not guaranteed that those operations will succeed.
     * If the modification operation fails, no indication is provided.
     * </p>
     * <h3>Example: Copy directories only</h3>
     * <pre>
     *  // only copy the directory structure
     *  FileUtils.copyDirectory(srcDir, destDir, DirectoryFileFilter.DIRECTORY);
     *  </pre>
     *
     * <h3>Example: Copy directories and txt files</h3>
     * <pre>
     *  // Create a filter for ".txt" files
     *  IOFileFilter txtSuffixFilter = FileFilterUtils.suffixFileFilter(".txt");
     *  IOFileFilter txtFiles = FileFilterUtils.andFileFilter(FileFileFilter.FILE, txtSuffixFilter);
     *
     *  // Create a filter for either directories or ".txt" files
     *  FileFilter filter = FileFilterUtils.orFileFilter(DirectoryFileFilter.DIRECTORY, txtFiles);
     *
     *  // Copy using the filter
     *  FileUtils.copyDirectory(srcDir, destDir, filter);
     *  </pre>
     *
     * @param srcDir  an existing directory to copy, must not be {@code null}
     * @param destDir the new directory, must not be {@code null}
     * @param filter  the filter to apply, null means copy all directories and files
     *                should be the same as the original
     *
     * @throws NullPointerException if source or destination is {@code null}
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs during copying
     * @since 1.4
     */
    public static void copyDirectory(final File srcDir, final File destDir,
                                     final FileFilter filter) throws IOException {
        copyDirectory(srcDir, destDir, filter, true);
    }

    /**
     * Copies a filtered directory to a new location.
     * <p>
     * This method copies the contents of the specified source directory
     * to within the specified destination directory.
     * <p>
     * The destination directory is created if it does not exist.
     * If the destination directory did exist, then this method merges
     * the source with the destination, with the source taking precedence.
     * <p>
     * <strong>Note:</strong> Setting <code>preserveFileDate</code> to
     * {@code true} tries to preserve the files' last modified
     * date/times using {@link File#setLastModified(long)}, however it is
     * not guaranteed that those operations will succeed.
     * If the modification operation fails, no indication is provided.
     * </p>
     * <h3>Example: Copy directories only</h3>
     * <pre>
     *  // only copy the directory structure
     *  FileUtils.copyDirectory(srcDir, destDir, DirectoryFileFilter.DIRECTORY, false);
     *  </pre>
     *
     * <h3>Example: Copy directories and txt files</h3>
     * <pre>
     *  // Create a filter for ".txt" files
     *  IOFileFilter txtSuffixFilter = FileFilterUtils.suffixFileFilter(".txt");
     *  IOFileFilter txtFiles = FileFilterUtils.andFileFilter(FileFileFilter.FILE, txtSuffixFilter);
     *
     *  // Create a filter for either directories or ".txt" files
     *  FileFilter filter = FileFilterUtils.orFileFilter(DirectoryFileFilter.DIRECTORY, txtFiles);
     *
     *  // Copy using the filter
     *  FileUtils.copyDirectory(srcDir, destDir, filter, false);
     *  </pre>
     *
     * @param srcDir           an existing directory to copy, must not be {@code null}
     * @param destDir          the new directory, must not be {@code null}
     * @param filter           the filter to apply, null means copy all directories and files
     * @param preserveFileDate true if the file date of the copy
     *                         should be the same as the original
     *
     * @throws NullPointerException if source or destination is {@code null}
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs during copying
     * @since 1.4
     */
    public static void copyDirectory(final File srcDir, final File destDir,
                                     final FileFilter filter, final boolean preserveFileDate) throws IOException {
        checkFileRequirements(srcDir, destDir);
        if (!srcDir.isDirectory()) {
            throw new IOException("Source '" + srcDir + "' exists but is not a directory");
        }
        if (srcDir.getCanonicalPath().equals(destDir.getCanonicalPath())) {
            throw new IOException("Source '" + srcDir + "' and destination '" + destDir + "' are the same");
        }

        // Cater for destination being directory within the source directory (see IO-141)
        List<String> exclusionList = null;
        if (destDir.getCanonicalPath().startsWith(srcDir.getCanonicalPath())) {
            final File[] srcFiles = filter == null ? srcDir.listFiles() : srcDir.listFiles(filter);
            if (srcFiles != null && srcFiles.length > 0) {
                exclusionList = new ArrayList<>(srcFiles.length);
                for (final File srcFile : srcFiles) {
                    final File copiedFile = new File(destDir, srcFile.getName());
                    exclusionList.add(copiedFile.getCanonicalPath());
                }
            }
        }
        doCopyDirectory(srcDir, destDir, filter, preserveFileDate, exclusionList);
    }

    /**
     * checks requirements for file copy
     * @param src the source file
     * @param dest the destination
     * @throws FileNotFoundException if the destination does not exist
     */
    private static void checkFileRequirements(final File src, final File dest) throws FileNotFoundException {
        if (src == null) {
            throw new NullPointerException("Source must not be null");
        }
        if (dest == null) {
            throw new NullPointerException("Destination must not be null");
        }
        if (!src.exists()) {
            throw new FileNotFoundException("Source '" + src + "' does not exist");
        }
    }

    /**
     * Internal copy directory method.
     *
     * @param srcDir           the validated source directory, must not be {@code null}
     * @param destDir          the validated destination directory, must not be {@code null}
     * @param filter           the filter to apply, null means copy all directories and files
     * @param preserveFileDate whether to preserve the file date
     * @param exclusionList    List of files and directories to exclude from the copy, may be null
     * @throws IOException if an error occurs
     * @since 1.1
     */
    private static void doCopyDirectory(final File srcDir, final File destDir, final FileFilter filter,
                                        final boolean preserveFileDate, final List<String> exclusionList)
            throws IOException {
        // recurse
        final File[] srcFiles = filter == null ? srcDir.listFiles() : srcDir.listFiles(filter);
        if (srcFiles == null) {  // null if abstract pathname does not denote a directory, or if an I/O error occurs
            throw new IOException("Failed to list contents of " + srcDir);
        }
        if (destDir.exists()) {
            if (destDir.isDirectory() == false) {
                throw new IOException("Destination '" + destDir + "' exists but is not a directory");
            }
        } else {
            if (!destDir.mkdirs() && !destDir.isDirectory()) {
                throw new IOException("Destination '" + destDir + "' directory cannot be created");
            }
        }
        if (destDir.canWrite() == false) {
            throw new IOException("Destination '" + destDir + "' cannot be written to");
        }
        for (final File srcFile : srcFiles) {
            final File dstFile = new File(destDir, srcFile.getName());
            if (exclusionList == null || !exclusionList.contains(srcFile.getCanonicalPath())) {
                if (srcFile.isDirectory()) {
                    doCopyDirectory(srcFile, dstFile, filter, preserveFileDate, exclusionList);
                } else {
                    doCopyFile(srcFile, dstFile, preserveFileDate);
                }
            }
        }

        // Do this last, as the above has probably affected directory metadata
        if (preserveFileDate) {
            destDir.setLastModified(srcDir.lastModified());
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Copies bytes from the URL <code>source</code> to a file
     * <code>destination</code>. The directories up to <code>destination</code>
     * will be created if they don't already exist. <code>destination</code>
     * will be overwritten if it already exists.
     * <p>
     * Warning: this method does not set a connection or read timeout and thus
     * might block forever. Use {@link #copyURLToFile(URL, File, int, int)}
     * with reasonable timeouts to prevent this.
     *
     * @param source      the <code>URL</code> to copy bytes from, must not be {@code null}
     * @param destination the non-directory <code>File</code> to write bytes to
     *                    (possibly overwriting), must not be {@code null}
     * @throws IOException if <code>source</code> URL cannot be opened
     * @throws IOException if <code>destination</code> is a directory
     * @throws IOException if <code>destination</code> cannot be written
     * @throws IOException if <code>destination</code> needs creating but can't be
     * @throws IOException if an IO error occurs during copying
     */
    public static void copyURLToFile(final URL source, final File destination) throws IOException {
        copyInputStreamToFile(source.openStream(), destination);
    }

    /**
     * Copies bytes from the URL <code>source</code> to a file
     * <code>destination</code>. The directories up to <code>destination</code>
     * will be created if they don't already exist. <code>destination</code>
     * will be overwritten if it already exists.
     *
     * @param source            the <code>URL</code> to copy bytes from, must not be {@code null}
     * @param destination       the non-directory <code>File</code> to write bytes to
     *                          (possibly overwriting), must not be {@code null}
     * @param connectionTimeout the number of milliseconds until this method
     *                          will timeout if no connection could be established to the <code>source</code>
     * @param readTimeout       the number of milliseconds until this method will
     *                          timeout if no data could be read from the <code>source</code>
     * @throws IOException if <code>source</code> URL cannot be opened
     * @throws IOException if <code>destination</code> is a directory
     * @throws IOException if <code>destination</code> cannot be written
     * @throws IOException if <code>destination</code> needs creating but can't be
     * @throws IOException if an IO error occurs during copying
     * @since 2.0
     */
    public static void copyURLToFile(final URL source, final File destination,
                                     final int connectionTimeout, final int readTimeout) throws IOException {
        final URLConnection connection = source.openConnection();
        connection.setConnectTimeout(connectionTimeout);
        connection.setReadTimeout(readTimeout);
        copyInputStreamToFile(connection.getInputStream(), destination);
    }

    /**
     * Copies bytes from an {@link InputStream} <code>source</code> to a file
     * <code>destination</code>. The directories up to <code>destination</code>
     * will be created if they don't already exist. <code>destination</code>
     * will be overwritten if it already exists.
     * The {@code source} stream is closed.
     * See {@link #copyToFile(InputStream, File)} for a method that does not close the input stream.
     *
     * @param source      the <code>InputStream</code> to copy bytes from, must not be {@code null}, will be closed
     * @param destination the non-directory <code>File</code> to write bytes to
     *                    (possibly overwriting), must not be {@code null}
     * @throws IOException if <code>destination</code> is a directory
     * @throws IOException if <code>destination</code> cannot be written
     * @throws IOException if <code>destination</code> needs creating but can't be
     * @throws IOException if an IO error occurs during copying
     * @since 2.0
     */
    public static void copyInputStreamToFile(final InputStream source, final File destination) throws IOException {
        try (InputStream in = source) {
            copyToFile(in, destination);
        }
    }

    /**
     * Copies bytes from an {@link InputStream} <code>source</code> to a file
     * <code>destination</code>. The directories up to <code>destination</code>
     * will be created if they don't already exist. <code>destination</code>
     * will be overwritten if it already exists.
     * The {@code source} stream is left open, e.g. for use with {@link java.util.zip.ZipInputStream ZipInputStream}.
     * See {@link #copyInputStreamToFile(InputStream, File)} for a method that closes the input stream.
     *
     * @param source      the <code>InputStream</code> to copy bytes from, must not be {@code null}
     * @param destination the non-directory <code>File</code> to write bytes to
     *                    (possibly overwriting), must not be {@code null}
     * @throws IOException if <code>destination</code> is a directory
     * @throws IOException if <code>destination</code> cannot be written
     * @throws IOException if <code>destination</code> needs creating but can't be
     * @throws IOException if an IO error occurs during copying
     * @since 2.5
     */
    public static void copyToFile(final InputStream source, final File destination) throws IOException {
        try (InputStream in = source;
             OutputStream out = openOutputStream(destination)) {
            IOUtils.copy(in, out);
        }
    }

    /**
     * Copies a file or directory to within another directory preserving the file dates.
     * <p>
     * This method copies the source file or directory, along all its contents, to a
     * directory of the same name in the specified destination directory.
     * <p>
     * The destination directory is created if it does not exist.
     * If the destination directory did exist, then this method merges
     * the source with the destination, with the source taking precedence.
     * <p>
     * <strong>Note:</strong> This method tries to preserve the files' last
     * modified date/times using {@link File#setLastModified(long)}, however
     * it is not guaranteed that those operations will succeed.
     * If the modification operation fails, no indication is provided.
     *
     * @param src      an existing file or directory to copy, must not be {@code null}
     * @param destDir  the directory to place the copy in, must not be {@code null}
     *
     * @throws NullPointerException if source or destination is {@code null}
     * @throws IOException if source or destination is invalid
     * @throws IOException if an IO error occurs during copying
     * @see #copyDirectoryToDirectory(File, File)
     * @see #copyFileToDirectory(File, File)
     * @since 2.6
     */
    public static void copyToDirectory(final File src, final File destDir) throws IOException {
        if (src == null) {
            throw new NullPointerException("Source must not be null");
        }
        if (src.isFile()) {
            copyFileToDirectory(src, destDir);
        } else if (src.isDirectory()) {
            copyDirectoryToDirectory(src, destDir);
        } else {
            throw new IOException("The source " + src + " does not exist");
        }
    }

    /**
     * Copies a files to a directory preserving each file's date.
     * <p>
     * This method copies the contents of the specified source files
     * to a file of the same name in the specified destination directory.
     * The destination directory is created if it does not exist.
     * If the destination file exists, then this method will overwrite it.
     * <p>
     * <strong>Note:</strong> This method tries to preserve the file's last
     * modified date/times using {@link File#setLastModified(long)}, however
     * it is not guaranteed that the operation will succeed.
     * If the modification operation fails, no indication is provided.
     *
     * @param srcs     a existing files to copy, must not be {@code null}
     * @param destDir  the directory to place the copy in, must not be {@code null}
     *
     * @throws NullPointerException if source or destination is null
     * @throws IOException if source or destination is invalid
     * @throws IOException if an IO error occurs during copying
     * @see #copyFileToDirectory(File, File)
     * @since 2.6
     */
    public static void copyToDirectory(final Iterable<File> srcs, final File destDir) throws IOException {
        if (srcs == null) {
            throw new NullPointerException("Sources must not be null");
        }
        for (final File src : srcs) {
            copyFileToDirectory(src, destDir);
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Deletes a directory recursively.
     *
     * @param directory directory to delete
     * @throws IOException              in case deletion is unsuccessful
     * @throws IllegalArgumentException if {@code directory} does not exist or is not a directory
     */
    public static void deleteDirectory(final File directory) throws IOException {
        if (!directory.exists()) {
            return;
        }

        if (!isSymlink(directory)) {
            cleanDirectory(directory);
        }

        if (!directory.delete()) {
            final String message =
                    "Unable to delete directory " + directory + ".";
            throw new IOException(message);
        }
    }

    /**
     * Deletes a file, never throwing an exception. If file is a directory, delete it and all sub-directories.
     * <p>
     * The difference between File.delete() and this method are:
     * <ul>
     * <li>A directory to be deleted does not have to be empty.</li>
     * <li>No exceptions are thrown when a file or directory cannot be deleted.</li>
     * </ul>
     *
     * @param file file or directory to delete, can be {@code null}
     * @return {@code true} if the file or directory was deleted, otherwise
     * {@code false}
     *
     * @since 1.4
     */
    public static boolean deleteQuietly(final File file) {
        if (file == null) {
            return false;
        }
        try {
            if (file.isDirectory()) {
                cleanDirectory(file);
            }
        } catch (final Exception ignored) {
        }

        try {
            return file.delete();
        } catch (final Exception ignored) {
            return false;
        }
    }

    /**
     * Determines whether the {@code parent} directory contains the {@code child} element (a file or directory).
     * <p>
     * Files are normalized before comparison.
     * </p>
     *
     * Edge cases:
     * <ul>
     * <li>A {@code directory} must not be null: if null, throw IllegalArgumentException</li>
     * <li>A {@code directory} must be a directory: if not a directory, throw IllegalArgumentException</li>
     * <li>A directory does not contain itself: return false</li>
     * <li>A null child file is not contained in any parent: return false</li>
     * </ul>
     *
     * @param directory the file to consider as the parent.
     * @param child     the file to consider as the child.
     * @return true is the candidate leaf is under by the specified composite. False otherwise.
     * @throws IOException              if an IO error occurs while checking the files.
     * @throws IllegalArgumentException if {@code directory} is null or not a directory.
     * @see FilenameUtils#directoryContains(String, String)
     * @since 2.2
     */
    public static boolean directoryContains(final File directory, final File child) throws IOException {

        // Fail fast against NullPointerException
        if (directory == null) {
            throw new IllegalArgumentException("Directory must not be null");
        }

        if (!directory.isDirectory()) {
            throw new IllegalArgumentException("Not a directory: " + directory);
        }

        if (child == null) {
            return false;
        }

        if (!directory.exists() || !child.exists()) {
            return false;
        }

        // Canonicalize paths (normalizes relative paths)
        final String canonicalParent = directory.getCanonicalPath();
        final String canonicalChild = child.getCanonicalPath();

        return FilenameUtils.directoryContains(canonicalParent, canonicalChild);
    }

    /**
     * Cleans a directory without deleting it.
     *
     * @param directory directory to clean
     * @throws IOException              in case cleaning is unsuccessful
     * @throws IllegalArgumentException if {@code directory} does not exist or is not a directory
     */
    public static void cleanDirectory(final File directory) throws IOException {
        final File[] files = verifiedListFiles(directory);

        IOException exception = null;
        for (final File file : files) {
            try {
                forceDelete(file);
            } catch (final IOException ioe) {
                exception = ioe;
            }
        }

        if (null != exception) {
            throw exception;
        }
    }

    /**
     * Lists files in a directory, asserting that the supplied directory satisfies exists and is a directory
     * @param directory The directory to list
     * @return The files in the directory, never null.
     * @throws IOException if an I/O error occurs
     */
    private static File[] verifiedListFiles(final File directory) throws IOException {
        if (!directory.exists()) {
            final String message = directory + " does not exist";
            throw new IllegalArgumentException(message);
        }

        if (!directory.isDirectory()) {
            final String message = directory + " is not a directory";
            throw new IllegalArgumentException(message);
        }

        final File[] files = directory.listFiles();
        if (files == null) {  // null if security restricted
            throw new IOException("Failed to list contents of " + directory);
        }
        return files;
    }

    //-----------------------------------------------------------------------
    /**
     * Waits for NFS to propagate a file creation, imposing a timeout.
     * <p>
     * This method repeatedly tests {@link File#exists()} until it returns
     * true up to the maximum time specified in seconds.
     *
     * @param file    the file to check, must not be {@code null}
     * @param seconds the maximum time in seconds to wait
     * @return true if file exists
     * @throws NullPointerException if the file is {@code null}
     */
    public static boolean waitFor(final File file, final int seconds) {
        final long finishAt = System.currentTimeMillis() + (seconds * 1000L);
        boolean wasInterrupted = false;
        try {
            while (!file.exists()) {
                final long remaining = finishAt -  System.currentTimeMillis();
                if (remaining < 0){
                    return false;
                }
                try {
                    Thread.sleep(Math.min(100, remaining));
                } catch (final InterruptedException ignore) {
                    wasInterrupted = true;
                } catch (final Exception ex) {
                    break;
                }
            }
        } finally {
            if (wasInterrupted) {
                Thread.currentThread().interrupt();
            }
        }
        return true;
    }

    //-----------------------------------------------------------------------
    /**
     * Reads the contents of a file into a String.
     * The file is always closed.
     *
     * @param file     the file to read, must not be {@code null}
     * @param encoding the encoding to use, {@code null} means platform default
     * @return the file contents, never {@code null}
     * @throws IOException in case of an I/O error
     * @since 2.3
     */
    public static String readFileToString(final File file, final Charset encoding) throws IOException {
        try (InputStream in = openInputStream(file)) {
            return IOUtils.toString(in, Charsets.toCharset(encoding));
        }
    }

    /**
     * Reads the contents of a file into a String. The file is always closed.
     *
     * @param file     the file to read, must not be {@code null}
     * @param encoding the encoding to use, {@code null} means platform default
     * @return the file contents, never {@code null}
     * @throws IOException                 in case of an I/O error
     * @throws java.nio.charset.UnsupportedCharsetException thrown instead of {@link java.io
     * .UnsupportedEncodingException} in version 2.2 if the encoding is not supported.
     * @since 2.3
     */
    public static String readFileToString(final File file, final String encoding) throws IOException {
        return readFileToString(file, Charsets.toCharset(encoding));
    }


    /**
     * Reads the contents of a file into a String using the default encoding for the VM.
     * The file is always closed.
     *
     * @param file the file to read, must not be {@code null}
     * @return the file contents, never {@code null}
     * @throws IOException in case of an I/O error
     * @since 1.3.1
     * @deprecated 2.5 use {@link #readFileToString(File, Charset)} instead (and specify the appropriate encoding)
     */
    @Deprecated
    public static String readFileToString(final File file) throws IOException {
        return readFileToString(file, Charset.defaultCharset());
    }

    /**
     * Reads the contents of a file into a byte array.
     * The file is always closed.
     *
     * @param file the file to read, must not be {@code null}
     * @return the file contents, never {@code null}
     * @throws IOException in case of an I/O error
     * @since 1.1
     */
    public static byte[] readFileToByteArray(final File file) throws IOException {
        try (InputStream in = openInputStream(file)) {
            final long fileLength = file.length();
            // file.length() may return 0 for system-dependent entities, treat 0 as unknown length - see IO-453
            return fileLength > 0 ? IOUtils.toByteArray(in, fileLength) : IOUtils.toByteArray(in);
        }
    }

    /**
     * Reads the contents of a file line by line to a List of Strings.
     * The file is always closed.
     *
     * @param file     the file to read, must not be {@code null}
     * @param encoding the encoding to use, {@code null} means platform default
     * @return the list of Strings representing each line in the file, never {@code null}
     * @throws IOException in case of an I/O error
     * @since 2.3
     */
    public static List<String> readLines(final File file, final Charset encoding) throws IOException {
        try (InputStream in = openInputStream(file)) {
            return IOUtils.readLines(in, Charsets.toCharset(encoding));
        }
    }

    /**
     * Reads the contents of a file line by line to a List of Strings. The file is always closed.
     *
     * @param file     the file to read, must not be {@code null}
     * @param encoding the encoding to use, {@code null} means platform default
     * @return the list of Strings representing each line in the file, never {@code null}
     * @throws IOException                 in case of an I/O error
     * @throws java.nio.charset.UnsupportedCharsetException thrown instead of {@link java.io
     * .UnsupportedEncodingException} in version 2.2 if the encoding is not supported.
     * @since 1.1
     */
    public static List<String> readLines(final File file, final String encoding) throws IOException {
        return readLines(file, Charsets.toCharset(encoding));
    }

    /**
     * Reads the contents of a file line by line to a List of Strings using the default encoding for the VM.
     * The file is always closed.
     *
     * @param file the file to read, must not be {@code null}
     * @return the list of Strings representing each line in the file, never {@code null}
     * @throws IOException in case of an I/O error
     * @since 1.3
     * @deprecated 2.5 use {@link #readLines(File, Charset)} instead (and specify the appropriate encoding)
     */
    @Deprecated
    public static List<String> readLines(final File file) throws IOException {
        return readLines(file, Charset.defaultCharset());
    }

    /**
     * Returns an Iterator for the lines in a <code>File</code>.
     * <p>
     * This method opens an <code>InputStream</code> for the file.
     * When you have finished with the iterator you should close the stream
     * to free internal resources. This can be done by calling the
     * {@link LineIterator#close()} or
     * {@link LineIterator#closeQuietly(LineIterator)} method.
     * <p>
     * The recommended usage pattern is:
     * <pre>
     * LineIterator it = FileUtils.lineIterator(file, "UTF-8");
     * try {
     *   while (it.hasNext()) {
     *     String line = it.nextLine();
     *     /// do something with line
     *   }
     * } finally {
     *   LineIterator.closeQuietly(iterator);
     * }
     * </pre>
     * <p>
     * If an exception occurs during the creation of the iterator, the
     * underlying stream is closed.
     *
     * @param file     the file to open for input, must not be {@code null}
     * @param encoding the encoding to use, {@code null} means platform default
     * @return an Iterator of the lines in the file, never {@code null}
     * @throws IOException in case of an I/O error (file closed)
     * @since 1.2
     */
    public static LineIterator lineIterator(final File file, final String encoding) throws IOException {
        InputStream in = null;
        try {
            in = openInputStream(file);
            return IOUtils.lineIterator(in, encoding);
        } catch (final IOException | RuntimeException ex) {
            try {
                if (in != null) {
                    in.close();
                }
            }
            catch (final IOException e) {
                ex.addSuppressed(e);
            }
            throw ex;
        }
    }

    /**
     * Returns an Iterator for the lines in a <code>File</code> using the default encoding for the VM.
     *
     * @param file the file to open for input, must not be {@code null}
     * @return an Iterator of the lines in the file, never {@code null}
     * @throws IOException in case of an I/O error (file closed)
     * @see #lineIterator(File, String)
     * @since 1.3
     */
    public static LineIterator lineIterator(final File file) throws IOException {
        return lineIterator(file, null);
    }

    //-----------------------------------------------------------------------

    /**
     * Writes a String to a file creating the file if it does not exist.
     * <p>
     * NOTE: As from v1.3, the parent directories of the file will be created
     * if they do not exist.
     *
     * @param file     the file to write
     * @param data     the content to write to the file
     * @param encoding the encoding to use, {@code null} means platform default
     * @throws IOException                          in case of an I/O error
     * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
     * @since 2.4
     */
    public static void writeStringToFile(final File file, final String data, final Charset encoding)
            throws IOException {
        writeStringToFile(file, data, encoding, false);
    }

    /**
     * Writes a String to a file creating the file if it does not exist.
     * <p>
     * NOTE: As from v1.3, the parent directories of the file will be created
     * if they do not exist.
     *
     * @param file     the file to write
     * @param data     the content to write to the file
     * @param encoding the encoding to use, {@code null} means platform default
     * @throws IOException                          in case of an I/O error
     * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
     */
    public static void writeStringToFile(final File file, final String data, final String encoding) throws IOException {
        writeStringToFile(file, data, encoding, false);
    }

    /**
     * Writes a String to a file creating the file if it does not exist.
     *
     * @param file     the file to write
     * @param data     the content to write to the file
     * @param encoding the encoding to use, {@code null} means platform default
     * @param append   if {@code true}, then the String will be added to the
     *                 end of the file rather than overwriting
     * @throws IOException in case of an I/O error
     * @since 2.3
     */
    public static void writeStringToFile(final File file, final String data, final Charset encoding,
                                         final boolean append) throws IOException {
        try (OutputStream out = openOutputStream(file, append)) {
            IOUtils.write(data, out, encoding);
        }
    }

    /**
     * Writes a String to a file creating the file if it does not exist.
     *
     * @param file     the file to write
     * @param data     the content to write to the file
     * @param encoding the encoding to use, {@code null} means platform default
     * @param append   if {@code true}, then the String will be added to the
     *                 end of the file rather than overwriting
     * @throws IOException                 in case of an I/O error
     * @throws java.nio.charset.UnsupportedCharsetException thrown instead of {@link java.io
     * .UnsupportedEncodingException} in version 2.2 if the encoding is not supported by the VM
     * @since 2.1
     */
    public static void writeStringToFile(final File file, final String data, final String encoding,
                                         final boolean append) throws IOException {
        writeStringToFile(file, data, Charsets.toCharset(encoding), append);
    }

    /**
     * Writes a String to a file creating the file if it does not exist using the default encoding for the VM.
     *
     * @param file the file to write
     * @param data the content to write to the file
     * @throws IOException in case of an I/O error
     * @deprecated 2.5 use {@link #writeStringToFile(File, String, Charset)} instead (and specify the appropriate encoding)
     */
    @Deprecated
    public static void writeStringToFile(final File file, final String data) throws IOException {
        writeStringToFile(file, data, Charset.defaultCharset(), false);
    }

    /**
     * Writes a String to a file creating the file if it does not exist using the default encoding for the VM.
     *
     * @param file   the file to write
     * @param data   the content to write to the file
     * @param append if {@code true}, then the String will be added to the
     *               end of the file rather than overwriting
     * @throws IOException in case of an I/O error
     * @since 2.1
     * @deprecated 2.5 use {@link #writeStringToFile(File, String, Charset, boolean)} instead (and specify the appropriate encoding)
     */
    @Deprecated
    public static void writeStringToFile(final File file, final String data, final boolean append) throws IOException {
        writeStringToFile(file, data, Charset.defaultCharset(), append);
    }

    /**
     * Writes a CharSequence to a file creating the file if it does not exist using the default encoding for the VM.
     *
     * @param file the file to write
     * @param data the content to write to the file
     * @throws IOException in case of an I/O error
     * @since 2.0
     * @deprecated 2.5 use {@link #write(File, CharSequence, Charset)} instead (and specify the appropriate encoding)
     */
    @Deprecated
    public static void write(final File file, final CharSequence data) throws IOException {
        write(file, data, Charset.defaultCharset(), false);
    }

    /**
     * Writes a CharSequence to a file creating the file if it does not exist using the default encoding for the VM.
     *
     * @param file   the file to write
     * @param data   the content to write to the file
     * @param append if {@code true}, then the data will be added to the
     *               end of the file rather than overwriting
     * @throws IOException in case of an I/O error
     * @since 2.1
     * @deprecated 2.5 use {@link #write(File, CharSequence, Charset, boolean)} instead (and specify the appropriate encoding)
     */
    @Deprecated
    public static void write(final File file, final CharSequence data, final boolean append) throws IOException {
        write(file, data, Charset.defaultCharset(), append);
    }

    /**
     * Writes a CharSequence to a file creating the file if it does not exist.
     *
     * @param file     the file to write
     * @param data     the content to write to the file
     * @param encoding the encoding to use, {@code null} means platform default
     * @throws IOException in case of an I/O error
     * @since 2.3
     */
    public static void write(final File file, final CharSequence data, final Charset encoding) throws IOException {
        write(file, data, encoding, false);
    }

    /**
     * Writes a CharSequence to a file creating the file if it does not exist.
     *
     * @param file     the file to write
     * @param data     the content to write to the file
     * @param encoding the encoding to use, {@code null} means platform default
     * @throws IOException                          in case of an I/O error
     * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
     * @since 2.0
     */
    public static void write(final File file, final CharSequence data, final String encoding) throws IOException {
        write(file, data, encoding, false);
    }

    /**
     * Writes a CharSequence to a file creating the file if it does not exist.
     *
     * @param file     the file to write
     * @param data     the content to write to the file
     * @param encoding the encoding to use, {@code null} means platform default
     * @param append   if {@code true}, then the data will be added to the
     *                 end of the file rather than overwriting
     * @throws IOException in case of an I/O error
     * @since 2.3
     */
    public static void write(final File file, final CharSequence data, final Charset encoding, final boolean append)
            throws IOException {
        final String str = data == null ? null : data.toString();
        writeStringToFile(file, str, encoding, append);
    }

    /**
     * Writes a CharSequence to a file creating the file if it does not exist.
     *
     * @param file     the file to write
     * @param data     the content to write to the file
     * @param encoding the encoding to use, {@code null} means platform default
     * @param append   if {@code true}, then the data will be added to the
     *                 end of the file rather than overwriting
     * @throws IOException                 in case of an I/O error
     * @throws java.nio.charset.UnsupportedCharsetException thrown instead of {@link java.io
     * .UnsupportedEncodingException} in version 2.2 if the encoding is not supported by the VM
     * @since 2.1
     */
    public static void write(final File file, final CharSequence data, final String encoding, final boolean append)
            throws IOException {
        write(file, data, Charsets.toCharset(encoding), append);
    }

    /**
     * Writes a byte array to a file creating the file if it does not exist.
     * <p>
     * NOTE: As from v1.3, the parent directories of the file will be created
     * if they do not exist.
     *
     * @param file the file to write to
     * @param data the content to write to the file
     * @throws IOException in case of an I/O error
     * @since 1.1
     */
    public static void writeByteArrayToFile(final File file, final byte[] data) throws IOException {
        writeByteArrayToFile(file, data, false);
    }

    /**
     * Writes a byte array to a file creating the file if it does not exist.
     *
     * @param file   the file to write to
     * @param data   the content to write to the file
     * @param append if {@code true}, then bytes will be added to the
     *               end of the file rather than overwriting
     * @throws IOException in case of an I/O error
     * @since 2.1
     */
    public static void writeByteArrayToFile(final File file, final byte[] data, final boolean append)
            throws IOException {
        writeByteArrayToFile(file, data, 0, data.length, append);
    }

    /**
     * Writes {@code len} bytes from the specified byte array starting
     * at offset {@code off} to a file, creating the file if it does
     * not exist.
     *
     * @param file the file to write to
     * @param data the content to write to the file
     * @param off  the start offset in the data
     * @param len  the number of bytes to write
     * @throws IOException in case of an I/O error
     * @since 2.5
     */
    public static void writeByteArrayToFile(final File file, final byte[] data, final int off, final int len)
            throws IOException {
        writeByteArrayToFile(file, data, off, len, false);
    }

    /**
     * Writes {@code len} bytes from the specified byte array starting
     * at offset {@code off} to a file, creating the file if it does
     * not exist.
     *
     * @param file   the file to write to
     * @param data   the content to write to the file
     * @param off    the start offset in the data
     * @param len    the number of bytes to write
     * @param append if {@code true}, then bytes will be added to the
     *               end of the file rather than overwriting
     * @throws IOException in case of an I/O error
     * @since 2.5
     */
    public static void writeByteArrayToFile(final File file, final byte[] data, final int off, final int len,
                                            final boolean append) throws IOException {
        try (OutputStream out = openOutputStream(file, append)) {
            out.write(data, off, len);
        }
    }

    /**
     * Writes the <code>toString()</code> value of each item in a collection to
     * the specified <code>File</code> line by line.
     * The specified character encoding and the default line ending will be used.
     * <p>
     * NOTE: As from v1.3, the parent directories of the file will be created
     * if they do not exist.
     *
     * @param file     the file to write to
     * @param encoding the encoding to use, {@code null} means platform default
     * @param lines    the lines to write, {@code null} entries produce blank lines
     * @throws IOException                          in case of an I/O error
     * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
     * @since 1.1
     */
    public static void writeLines(final File file, final String encoding, final Collection<?> lines)
            throws IOException {
        writeLines(file, encoding, lines, null, false);
    }

    /**
     * Writes the <code>toString()</code> value of each item in a collection to
     * the specified <code>File</code> line by line, optionally appending.
     * The specified character encoding and the default line ending will be used.
     *
     * @param file     the file to write to
     * @param encoding the encoding to use, {@code null} means platform default
     * @param lines    the lines to write, {@code null} entries produce blank lines
     * @param append   if {@code true}, then the lines will be added to the
     *                 end of the file rather than overwriting
     * @throws IOException                          in case of an I/O error
     * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
     * @since 2.1
     */
    public static void writeLines(final File file, final String encoding, final Collection<?> lines,
                                  final boolean append) throws IOException {
        writeLines(file, encoding, lines, null, append);
    }

    /**
     * Writes the <code>toString()</code> value of each item in a collection to
     * the specified <code>File</code> line by line.
     * The default VM encoding and the default line ending will be used.
     *
     * @param file  the file to write to
     * @param lines the lines to write, {@code null} entries produce blank lines
     * @throws IOException in case of an I/O error
     * @since 1.3
     */
    public static void writeLines(final File file, final Collection<?> lines) throws IOException {
        writeLines(file, null, lines, null, false);
    }

    /**
     * Writes the <code>toString()</code> value of each item in a collection to
     * the specified <code>File</code> line by line.
     * The default VM encoding and the default line ending will be used.
     *
     * @param file   the file to write to
     * @param lines  the lines to write, {@code null} entries produce blank lines
     * @param append if {@code true}, then the lines will be added to the
     *               end of the file rather than overwriting
     * @throws IOException in case of an I/O error
     * @since 2.1
     */
    public static void writeLines(final File file, final Collection<?> lines, final boolean append) throws IOException {
        writeLines(file, null, lines, null, append);
    }

    /**
     * Writes the <code>toString()</code> value of each item in a collection to
     * the specified <code>File</code> line by line.
     * The specified character encoding and the line ending will be used.
     * <p>
     * NOTE: As from v1.3, the parent directories of the file will be created
     * if they do not exist.
     *
     * @param file       the file to write to
     * @param encoding   the encoding to use, {@code null} means platform default
     * @param lines      the lines to write, {@code null} entries produce blank lines
     * @param lineEnding the line separator to use, {@code null} is system default
     * @throws IOException                          in case of an I/O error
     * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
     * @since 1.1
     */
    public static void writeLines(final File file, final String encoding, final Collection<?> lines,
                                  final String lineEnding) throws IOException {
        writeLines(file, encoding, lines, lineEnding, false);
    }

    /**
     * Writes the <code>toString()</code> value of each item in a collection to
     * the specified <code>File</code> line by line.
     * The specified character encoding and the line ending will be used.
     *
     * @param file       the file to write to
     * @param encoding   the encoding to use, {@code null} means platform default
     * @param lines      the lines to write, {@code null} entries produce blank lines
     * @param lineEnding the line separator to use, {@code null} is system default
     * @param append     if {@code true}, then the lines will be added to the
     *                   end of the file rather than overwriting
     * @throws IOException                          in case of an I/O error
     * @throws java.io.UnsupportedEncodingException if the encoding is not supported by the VM
     * @since 2.1
     */
    public static void writeLines(final File file, final String encoding, final Collection<?> lines,
                                  final String lineEnding, final boolean append) throws IOException {
        try (OutputStream out = new BufferedOutputStream(openOutputStream(file, append))) {
            IOUtils.writeLines(lines, lineEnding, out, encoding);
        }
    }

    /**
     * Writes the <code>toString()</code> value of each item in a collection to
     * the specified <code>File</code> line by line.
     * The default VM encoding and the specified line ending will be used.
     *
     * @param file       the file to write to
     * @param lines      the lines to write, {@code null} entries produce blank lines
     * @param lineEnding the line separator to use, {@code null} is system default
     * @throws IOException in case of an I/O error
     * @since 1.3
     */
    public static void writeLines(final File file, final Collection<?> lines, final String lineEnding)
            throws IOException {
        writeLines(file, null, lines, lineEnding, false);
    }

    /**
     * Writes the <code>toString()</code> value of each item in a collection to
     * the specified <code>File</code> line by line.
     * The default VM encoding and the specified line ending will be used.
     *
     * @param file       the file to write to
     * @param lines      the lines to write, {@code null} entries produce blank lines
     * @param lineEnding the line separator to use, {@code null} is system default
     * @param append     if {@code true}, then the lines will be added to the
     *                   end of the file rather than overwriting
     * @throws IOException in case of an I/O error
     * @since 2.1
     */
    public static void writeLines(final File file, final Collection<?> lines, final String lineEnding,
                                  final boolean append) throws IOException {
        writeLines(file, null, lines, lineEnding, append);
    }

    //-----------------------------------------------------------------------
    /**
     * Deletes a file. If file is a directory, delete it and all sub-directories.
     * <p>
     * The difference between File.delete() and this method are:
     * <ul>
     * <li>A directory to be deleted does not have to be empty.</li>
     * <li>You get exceptions when a file or directory cannot be deleted.
     * (java.io.File methods returns a boolean)</li>
     * </ul>
     *
     * @param file file or directory to delete, must not be {@code null}
     * @throws NullPointerException  if the directory is {@code null}
     * @throws FileNotFoundException if the file was not found
     * @throws IOException           in case deletion is unsuccessful
     */
    public static void forceDelete(final File file) throws IOException {
        if (file.isDirectory()) {
            deleteDirectory(file);
        } else {
            final boolean filePresent = file.exists();
            if (!file.delete()) {
                if (!filePresent) {
                    throw new FileNotFoundException("File does not exist: " + file);
                }
                final String message =
                        "Unable to delete file: " + file;
                throw new IOException(message);
            }
        }
    }

    /**
     * Schedules a file to be deleted when JVM exits.
     * If file is directory delete it and all sub-directories.
     *
     * @param file file or directory to delete, must not be {@code null}
     * @throws NullPointerException if the file is {@code null}
     * @throws IOException          in case deletion is unsuccessful
     */
    public static void forceDeleteOnExit(final File file) throws IOException {
        if (file.isDirectory()) {
            deleteDirectoryOnExit(file);
        } else {
            file.deleteOnExit();
        }
    }

    /**
     * Schedules a directory recursively for deletion on JVM exit.
     *
     * @param directory directory to delete, must not be {@code null}
     * @throws NullPointerException if the directory is {@code null}
     * @throws IOException          in case deletion is unsuccessful
     */
    private static void deleteDirectoryOnExit(final File directory) throws IOException {
        if (!directory.exists()) {
            return;
        }

        directory.deleteOnExit();
        if (!isSymlink(directory)) {
            cleanDirectoryOnExit(directory);
        }
    }

    /**
     * Cleans a directory without deleting it.
     *
     * @param directory directory to clean, must not be {@code null}
     * @throws NullPointerException if the directory is {@code null}
     * @throws IOException          in case cleaning is unsuccessful
     */
    private static void cleanDirectoryOnExit(final File directory) throws IOException {
        final File[] files = verifiedListFiles(directory);

        IOException exception = null;
        for (final File file : files) {
            try {
                forceDeleteOnExit(file);
            } catch (final IOException ioe) {
                exception = ioe;
            }
        }

        if (null != exception) {
            throw exception;
        }
    }

    /**
     * Makes a directory, including any necessary but nonexistent parent
     * directories. If a file already exists with specified name but it is
     * not a directory then an IOException is thrown.
     * If the directory cannot be created (or does not already exist)
     * then an IOException is thrown.
     *
     * @param directory directory to create, must not be {@code null}
     * @throws NullPointerException if the directory is {@code null}
     * @throws IOException          if the directory cannot be created or the file already exists but is not a directory
     */
    public static void forceMkdir(final File directory) throws IOException {
        if (directory.exists()) {
            if (!directory.isDirectory()) {
                final String message =
                        "File "
                                + directory
                                + " exists and is "
                                + "not a directory. Unable to create directory.";
                throw new IOException(message);
            }
        } else {
            if (!directory.mkdirs()) {
                // Double-check that some other thread or process hasn't made
                // the directory in the background
                if (!directory.isDirectory()) {
                    final String message =
                            "Unable to create directory " + directory;
                    throw new IOException(message);
                }
            }
        }
    }

    /**
     * Makes any necessary but nonexistent parent directories for a given File. If the parent directory cannot be
     * created then an IOException is thrown.
     *
     * @param file file with parent to create, must not be {@code null}
     * @throws NullPointerException if the file is {@code null}
     * @throws IOException          if the parent directory cannot be created
     * @since 2.5
     */
    public static void forceMkdirParent(final File file) throws IOException {
        final File parent = file.getParentFile();
        if (parent == null) {
            return;
        }
        forceMkdir(parent);
    }

    //-----------------------------------------------------------------------
    /**
     * Returns the size of the specified file or directory. If the provided
     * {@link File} is a regular file, then the file's length is returned.
     * If the argument is a directory, then the size of the directory is
     * calculated recursively. If a directory or subdirectory is security
     * restricted, its size will not be included.
     * <p>
     * Note that overflow is not detected, and the return value may be negative if
     * overflow occurs. See {@link #sizeOfAsBigInteger(File)} for an alternative
     * method that does not overflow.
     *
     * @param file the regular file or directory to return the size
     *             of (must not be {@code null}).
     *
     * @return the length of the file, or recursive size of the directory,
     * provided (in bytes).
     *
     * @throws NullPointerException     if the file is {@code null}
     * @throws IllegalArgumentException if the file does not exist.
     *
     * @since 2.0
     */
    public static long sizeOf(final File file) {

        if (!file.exists()) {
            final String message = file + " does not exist";
            throw new IllegalArgumentException(message);
        }

        if (file.isDirectory()) {
            return sizeOfDirectory0(file); // private method; expects directory
        } else {
            return file.length();
        }

    }

    /**
     * Returns the size of the specified file or directory. If the provided
     * {@link File} is a regular file, then the file's length is returned.
     * If the argument is a directory, then the size of the directory is
     * calculated recursively. If a directory or subdirectory is security
     * restricted, its size will not be included.
     *
     * @param file the regular file or directory to return the size
     *             of (must not be {@code null}).
     *
     * @return the length of the file, or recursive size of the directory,
     * provided (in bytes).
     *
     * @throws NullPointerException     if the file is {@code null}
     * @throws IllegalArgumentException if the file does not exist.
     *
     * @since 2.4
     */
    public static BigInteger sizeOfAsBigInteger(final File file) {

        if (!file.exists()) {
            final String message = file + " does not exist";
            throw new IllegalArgumentException(message);
        }

        if (file.isDirectory()) {
            return sizeOfDirectoryBig0(file); // internal method
        } else {
            return BigInteger.valueOf(file.length());
        }

    }

    /**
     * Counts the size of a directory recursively (sum of the length of all files).
     * <p>
     * Note that overflow is not detected, and the return value may be negative if
     * overflow occurs. See {@link #sizeOfDirectoryAsBigInteger(File)} for an alternative
     * method that does not overflow.
     *
     * @param directory directory to inspect, must not be {@code null}
     * @return size of directory in bytes, 0 if directory is security restricted, a negative number when the real total
     * is greater than {@link Long#MAX_VALUE}.
     * @throws NullPointerException if the directory is {@code null}
     */
    public static long sizeOfDirectory(final File directory) {
        checkDirectory(directory);
        return sizeOfDirectory0(directory);
    }

    // Private method, must be invoked will a directory parameter

    /**
     * the size of a director
     * @param directory the directory to check
     * @return the size
     */
    private static long sizeOfDirectory0(final File directory) {
        final File[] files = directory.listFiles();
        if (files == null) {  // null if security restricted
            return 0L;
        }
        long size = 0;

        for (final File file : files) {
            try {
                if (!isSymlink(file)) {
                    size += sizeOf0(file); // internal method
                    if (size < 0) {
                        break;
                    }
                }
            } catch (final IOException ioe) {
                // Ignore exceptions caught when asking if a File is a symlink.
            }
        }

        return size;
    }

    // Internal method - does not check existence

    /**
     * the size of a file
     * @param file the file to check
     * @return the size of the file
     */
    private static long sizeOf0(final File file) {
        if (file.isDirectory()) {
            return sizeOfDirectory0(file);
        } else {
            return file.length(); // will be 0 if file does not exist
        }
    }

    /**
     * Counts the size of a directory recursively (sum of the length of all files).
     *
     * @param directory directory to inspect, must not be {@code null}
     * @return size of directory in bytes, 0 if directory is security restricted.
     * @throws NullPointerException if the directory is {@code null}
     * @since 2.4
     */
    public static BigInteger sizeOfDirectoryAsBigInteger(final File directory) {
        checkDirectory(directory);
        return sizeOfDirectoryBig0(directory);
    }

    // Must be called with a directory

    /**
     * Finds the size of a directory
     *
     * @param directory The directory
     * @return the size
     */
    private static BigInteger sizeOfDirectoryBig0(final File directory) {
        final File[] files = directory.listFiles();
        if (files == null) {  // null if security restricted
            return BigInteger.ZERO;
        }
        BigInteger size = BigInteger.ZERO;

        for (final File file : files) {
            try {
                if (!isSymlink(file)) {
                    size = size.add(sizeOfBig0(file));
                }
            } catch (final IOException ioe) {
                // Ignore exceptions caught when asking if a File is a symlink.
            }
        }

        return size;
    }

    // internal method; if file does not exist will return 0

    /**
     * Returns the size of a file
     * @param fileOrDir The file
     * @return the size
     */
    private static BigInteger sizeOfBig0(final File fileOrDir) {
        if (fileOrDir.isDirectory()) {
            return sizeOfDirectoryBig0(fileOrDir);
        } else {
            return BigInteger.valueOf(fileOrDir.length());
        }
    }

    /**
     * Checks that the given {@code File} exists and is a directory.
     *
     * @param directory The {@code File} to check.
     * @throws IllegalArgumentException if the given {@code File} does not exist or is not a directory.
     */
    private static void checkDirectory(final File directory) {
        if (!directory.exists()) {
            throw new IllegalArgumentException(directory + " does not exist");
        }
        if (!directory.isDirectory()) {
            throw new IllegalArgumentException(directory + " is not a directory");
        }
    }

    //-----------------------------------------------------------------------
    /**
     * Tests if the specified <code>File</code> is newer than the reference
     * <code>File</code>.
     *
     * @param file      the <code>File</code> of which the modification date must
     *                  be compared, must not be {@code null}
     * @param reference the <code>File</code> of which the modification date
     *                  is used, must not be {@code null}
     * @return true if the <code>File</code> exists and has been modified more
     * recently than the reference <code>File</code>
     * @throws IllegalArgumentException if the file is {@code null}
     * @throws IllegalArgumentException if the reference file is {@code null} or doesn't exist
     */
    public static boolean isFileNewer(final File file, final File reference) {
        if (reference == null) {
            throw new IllegalArgumentException("No specified reference file");
        }
        if (!reference.exists()) {
            throw new IllegalArgumentException("The reference file '"
                    + reference + "' doesn't exist");
        }
        return isFileNewer(file, reference.lastModified());
    }

    /**
     * Tests if the specified <code>File</code> is newer than the specified
     * <code>Date</code>.
     *
     * @param file the <code>File</code> of which the modification date
     *             must be compared, must not be {@code null}
     * @param date the date reference, must not be {@code null}
     * @return true if the <code>File</code> exists and has been modified
     * after the given <code>Date</code>.
     * @throws IllegalArgumentException if the file is {@code null}
     * @throws IllegalArgumentException if the date is {@code null}
     */
    public static boolean isFileNewer(final File file, final Date date) {
        if (date == null) {
            throw new IllegalArgumentException("No specified date");
        }
        return isFileNewer(file, date.getTime());
    }

    /**
     * Tests if the specified <code>File</code> is newer than the specified
     * time reference.
     *
     * @param file       the <code>File</code> of which the modification date must
     *                   be compared, must not be {@code null}
     * @param timeMillis the time reference measured in milliseconds since the
     *                   epoch (00:00:00 GMT, January 1, 1970)
     * @return true if the <code>File</code> exists and has been modified after
     * the given time reference.
     * @throws IllegalArgumentException if the file is {@code null}
     */
    public static boolean isFileNewer(final File file, final long timeMillis) {
        if (file == null) {
            throw new IllegalArgumentException("No specified file");
        }
        if (!file.exists()) {
            return false;
        }
        return file.lastModified() > timeMillis;
    }


    //-----------------------------------------------------------------------
    /**
     * Tests if the specified <code>File</code> is older than the reference
     * <code>File</code>.
     *
     * @param file      the <code>File</code> of which the modification date must
     *                  be compared, must not be {@code null}
     * @param reference the <code>File</code> of which the modification date
     *                  is used, must not be {@code null}
     * @return true if the <code>File</code> exists and has been modified before
     * the reference <code>File</code>
     * @throws IllegalArgumentException if the file is {@code null}
     * @throws IllegalArgumentException if the reference file is {@code null} or doesn't exist
     */
    public static boolean isFileOlder(final File file, final File reference) {
        if (reference == null) {
            throw new IllegalArgumentException("No specified reference file");
        }
        if (!reference.exists()) {
            throw new IllegalArgumentException("The reference file '"
                    + reference + "' doesn't exist");
        }
        return isFileOlder(file, reference.lastModified());
    }

    /**
     * Tests if the specified <code>File</code> is older than the specified
     * <code>Date</code>.
     *
     * @param file the <code>File</code> of which the modification date
     *             must be compared, must not be {@code null}
     * @param date the date reference, must not be {@code null}
     * @return true if the <code>File</code> exists and has been modified
     * before the given <code>Date</code>.
     * @throws IllegalArgumentException if the file is {@code null}
     * @throws IllegalArgumentException if the date is {@code null}
     */
    public static boolean isFileOlder(final File file, final Date date) {
        if (date == null) {
            throw new IllegalArgumentException("No specified date");
        }
        return isFileOlder(file, date.getTime());
    }

    /**
     * Tests if the specified <code>File</code> is older than the specified
     * time reference.
     *
     * @param file       the <code>File</code> of which the modification date must
     *                   be compared, must not be {@code null}
     * @param timeMillis the time reference measured in milliseconds since the
     *                   epoch (00:00:00 GMT, January 1, 1970)
     * @return true if the <code>File</code> exists and has been modified before
     * the given time reference.
     * @throws IllegalArgumentException if the file is {@code null}
     */
    public static boolean isFileOlder(final File file, final long timeMillis) {
        if (file == null) {
            throw new IllegalArgumentException("No specified file");
        }
        if (!file.exists()) {
            return false;
        }
        return file.lastModified() < timeMillis;
    }

    //-----------------------------------------------------------------------
    /**
     * Computes the checksum of a file using the CRC32 checksum routine.
     * The value of the checksum is returned.
     *
     * @param file the file to checksum, must not be {@code null}
     * @return the checksum value
     * @throws NullPointerException     if the file or checksum is {@code null}
     * @throws IllegalArgumentException if the file is a directory
     * @throws IOException              if an IO error occurs reading the file
     * @since 1.3
     */
    public static long checksumCRC32(final File file) throws IOException {
        final CRC32 crc = new CRC32();
        checksum(file, crc);
        return crc.getValue();
    }

    /**
     * Computes the checksum of a file using the specified checksum object.
     * Multiple files may be checked using one <code>Checksum</code> instance
     * if desired simply by reusing the same checksum object.
     * For example:
     * <pre>
     *   long csum = FileUtils.checksum(file, new CRC32()).getValue();
     * </pre>
     *
     * @param file     the file to checksum, must not be {@code null}
     * @param checksum the checksum object to be used, must not be {@code null}
     * @return the checksum specified, updated with the content of the file
     * @throws NullPointerException     if the file or checksum is {@code null}
     * @throws IllegalArgumentException if the file is a directory
     * @throws IOException              if an IO error occurs reading the file
     * @since 1.3
     */
    public static Checksum checksum(final File file, final Checksum checksum) throws IOException {
        if (file.isDirectory()) {
            throw new IllegalArgumentException("Checksums can't be computed on directories");
        }
        try (InputStream in = new CheckedInputStream(new FileInputStream(file), checksum)) {
            IOUtils.copy(in, new NullOutputStream());
        }
        return checksum;
    }

    /**
     * Moves a directory.
     * <p>
     * When the destination directory is on another file system, do a "copy and delete".
     *
     * @param srcDir  the directory to be moved
     * @param destDir the destination directory
     * @throws NullPointerException if source or destination is {@code null}
     * @throws FileExistsException  if the destination directory exists
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs moving the file
     * @since 1.4
     */
    public static void moveDirectory(final File srcDir, final File destDir) throws IOException {
        if (srcDir == null) {
            throw new NullPointerException("Source must not be null");
        }
        if (destDir == null) {
            throw new NullPointerException("Destination must not be null");
        }
        if (!srcDir.exists()) {
            throw new FileNotFoundException("Source '" + srcDir + "' does not exist");
        }
        if (!srcDir.isDirectory()) {
            throw new IOException("Source '" + srcDir + "' is not a directory");
        }
        if (destDir.exists()) {
            throw new FileExistsException("Destination '" + destDir + "' already exists");
        }
        final boolean rename = srcDir.renameTo(destDir);
        if (!rename) {
            if (destDir.getCanonicalPath().startsWith(srcDir.getCanonicalPath() + File.separator)) {
                throw new IOException("Cannot move directory: " + srcDir + " to a subdirectory of itself: " + destDir);
            }
            copyDirectory(srcDir, destDir);
            deleteDirectory(srcDir);
            if (srcDir.exists()) {
                throw new IOException("Failed to delete original directory '" + srcDir +
                        "' after copy to '" + destDir + "'");
            }
        }
    }

    /**
     * Moves a directory to another directory.
     *
     * @param src           the file to be moved
     * @param destDir       the destination file
     * @param createDestDir If {@code true} create the destination directory,
     *                      otherwise if {@code false} throw an IOException
     * @throws NullPointerException if source or destination is {@code null}
     * @throws FileExistsException  if the directory exists in the destination directory
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs moving the file
     * @since 1.4
     */
    public static void moveDirectoryToDirectory(final File src, final File destDir, final boolean createDestDir)
            throws IOException {
        if (src == null) {
            throw new NullPointerException("Source must not be null");
        }
        if (destDir == null) {
            throw new NullPointerException("Destination directory must not be null");
        }
        if (!destDir.exists() && createDestDir) {
            destDir.mkdirs();
        }
        if (!destDir.exists()) {
            throw new FileNotFoundException("Destination directory '" + destDir +
                    "' does not exist [createDestDir=" + createDestDir + "]");
        }
        if (!destDir.isDirectory()) {
            throw new IOException("Destination '" + destDir + "' is not a directory");
        }
        moveDirectory(src, new File(destDir, src.getName()));

    }

    /**
     * Moves a file.
     * <p>
     * When the destination file is on another file system, do a "copy and delete".
     *
     * @param srcFile  the file to be moved
     * @param destFile the destination file
     * @throws NullPointerException if source or destination is {@code null}
     * @throws FileExistsException  if the destination file exists
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs moving the file
     * @since 1.4
     */
    public static void moveFile(final File srcFile, final File destFile) throws IOException {
        if (srcFile == null) {
            throw new NullPointerException("Source must not be null");
        }
        if (destFile == null) {
            throw new NullPointerException("Destination must not be null");
        }
        if (!srcFile.exists()) {
            throw new FileNotFoundException("Source '" + srcFile + "' does not exist");
        }
        if (srcFile.isDirectory()) {
            throw new IOException("Source '" + srcFile + "' is a directory");
        }
        if (destFile.exists()) {
            throw new FileExistsException("Destination '" + destFile + "' already exists");
        }
        if (destFile.isDirectory()) {
            throw new IOException("Destination '" + destFile + "' is a directory");
        }
        final boolean rename = srcFile.renameTo(destFile);
        if (!rename) {
            copyFile(srcFile, destFile);
            if (!srcFile.delete()) {
                FileUtils.deleteQuietly(destFile);
                throw new IOException("Failed to delete original file '" + srcFile +
                        "' after copy to '" + destFile + "'");
            }
        }
    }

    /**
     * Moves a file to a directory.
     *
     * @param srcFile       the file to be moved
     * @param destDir       the destination file
     * @param createDestDir If {@code true} create the destination directory,
     *                      otherwise if {@code false} throw an IOException
     * @throws NullPointerException if source or destination is {@code null}
     * @throws FileExistsException  if the destination file exists
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs moving the file
     * @since 1.4
     */
    public static void moveFileToDirectory(final File srcFile, final File destDir, final boolean createDestDir)
            throws IOException {
        if (srcFile == null) {
            throw new NullPointerException("Source must not be null");
        }
        if (destDir == null) {
            throw new NullPointerException("Destination directory must not be null");
        }
        if (!destDir.exists() && createDestDir) {
            destDir.mkdirs();
        }
        if (!destDir.exists()) {
            throw new FileNotFoundException("Destination directory '" + destDir +
                    "' does not exist [createDestDir=" + createDestDir + "]");
        }
        if (!destDir.isDirectory()) {
            throw new IOException("Destination '" + destDir + "' is not a directory");
        }
        moveFile(srcFile, new File(destDir, srcFile.getName()));
    }

    /**
     * Moves a file or directory to the destination directory.
     * <p>
     * When the destination is on another file system, do a "copy and delete".
     *
     * @param src           the file or directory to be moved
     * @param destDir       the destination directory
     * @param createDestDir If {@code true} create the destination directory,
     *                      otherwise if {@code false} throw an IOException
     * @throws NullPointerException if source or destination is {@code null}
     * @throws FileExistsException  if the directory or file exists in the destination directory
     * @throws IOException          if source or destination is invalid
     * @throws IOException          if an IO error occurs moving the file
     * @since 1.4
     */
    public static void moveToDirectory(final File src, final File destDir, final boolean createDestDir)
            throws IOException {
        if (src == null) {
            throw new NullPointerException("Source must not be null");
        }
        if (destDir == null) {
            throw new NullPointerException("Destination must not be null");
        }
        if (!src.exists()) {
            throw new FileNotFoundException("Source '" + src + "' does not exist");
        }
        if (src.isDirectory()) {
            moveDirectoryToDirectory(src, destDir, createDestDir);
        } else {
            moveFileToDirectory(src, destDir, createDestDir);
        }
    }

    /**
     * Determines whether the specified file is a Symbolic Link rather than an actual file.
     * <p>
     * Will not return true if there is a Symbolic Link anywhere in the path,
     * only if the specific file is.
     * <p>
     * When using jdk1.7, this method delegates to {@code boolean java.nio.file.Files.isSymbolicLink(Path path)}
     *
     * <b>Note:</b> the current implementation always returns {@code false} if running on
     * jkd1.6 and the system is detected as Windows using {@link FilenameUtils#isSystemWindows()}
     * <p>
     * For code that runs on Java 1.7 or later, use the following method instead:
     * <br>
     * {@code boolean java.nio.file.Files.isSymbolicLink(Path path)}
     * @param file the file to check
     * @return true if the file is a Symbolic Link
     * @throws IOException if an IO error occurs while checking the file
     * @since 2.0
     */
    public static boolean isSymlink(final File file) throws IOException {
        if (file == null) {
            throw new NullPointerException("File must not be null");
        }
        return Files.isSymbolicLink(file.toPath());
    }
}
