This package defines an interface (IOFileFilter) that combines both {@link java.io.FileFilter} and {@link java.io.FilenameFilter}. Besides that the package offers a series of ready-to-use implementations of the IOFileFilter interface including implementation that allow you to combine other such filters.

These filter can be used to list files or in {@link java.awt.FileDialog}, for example.

There are a number of 'primitive' filters:
DirectoryFilter | Only accept directories
PrefixFileFilter | Filter based on a prefix
SuffixFileFilter | Filter based on a suffix
NameFileFilter | Filter based on a filename
WildcardFileFilter | Filter based on wildcards
AgeFileFilter | Filter based on last modified time of file
SizeFileFilter | Filter based on file size

And there are five 'boolean' filters:
TrueFileFilter | Accept all files
FalseFileFilter | Accept no files
NotFileFilter | Applies a logical NOT to an existing filter
AndFileFilter | Combines two filters using a logical AND
OrFileFilter | Combines two filter using a logical OR

These boolean FilenameFilters can be nested, to allow arbitrary expressions. For example, here is how one could print all non-directory files in the current directory, starting with "A", and ending in ".java" or ".class":

      File dir = new File(".");
      String[] files = dir.list(
        new AndFileFilter(
          new AndFileFilter(
            new PrefixFileFilter("A"),
            new OrFileFilter(
              new SuffixFileFilter(".class"),
              new SuffixFileFilter(".java")
            )
          ),
          new NotFileFilter(
            new DirectoryFileFilter()
          )
        )
      );
      for ( int i=0; i<files.length; i++ ) {
        System.out.println(files[i]);
      }

This package also contains a utility class: FileFilterUtils. It allows you to use all file filters without having to put them in the import section. Here's how the above example will look using FileFilterUtils:

      File dir = new File(".");
      String[] files = dir.list(
        FileFilterUtils.andFileFilter(
          FileFilterUtils.andFileFilter(
            FileFilterUtils.prefixFileFilter("A"),
            FileFilterUtils.orFileFilter(
              FileFilterUtils.suffixFileFilter(".class"),
              FileFilterUtils.suffixFileFilter(".java")
            )
          ),
          FileFilterUtils.notFileFilter(
            FileFilterUtils.directoryFileFilter()
          )
        )
      );
      for ( int i=0; i<files.length; i++ ) {
        System.out.println(files[i]);
      }

There are a few other goodies in that class so please have a look at the documentation in detail.