apache common IO

This package defines utility classes for working with streams, readers, writers and files. The most commonly used classes are described here:

IOUtils is the most frequently used class. It provides operations to read, write, copy and close streams.

FileUtils provides operations based around the JDK File class. These include reading, writing, copying, comparing and deleting.

FilenameUtils provides utilities based on filenames. This utility class manipulates filenames without using File objects. It aims to simplify the transition between Windows and Unix. Before using this class however, you should consider whether you should be using File objects.

FileSystemUtils allows access to the filing system in ways the JDK does not support. At present this allows you to get the free space on a drive.

EndianUtils swaps data between Big-Endian and Little-Endian formats.

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:

And there are five 'boolean' filters:

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.

This package provides implementations of input classes, such as InputStream and Reader.

This package provides implementations of output classes, such as OutputStream and Writer.