Commons IO is a package of Java utility classes for java.io's hierarchy.  
Classes in this package are considered to be so standard and of such high 
reuse as to justify existence in java.io.

Commons IO contains utility classes, stream implementations, file filters, 
and endian transformation classes.


Compatibility with 1.2
----------------------
Binary compatible - Yes

Source compatible - Yes

Semantic compatible - Yes
  Check the bug fixes section for semantic bug fixes


Deprecations from 1.2
---------------------
- WildcardFilter deprecated, replaced by WildcardFileFilter
  - old class only accepted files, thus had a confusing dual purpose

- FileSystemUtils.freeSpace deprecated, replaced by freeSpaceKb
  - freeSpace returns a result that varies by operating system and
    thus isn't that useful
  - freeSpaceKb returns much better and more consistent results
  - freeSpaceKb existed in v1.2, so this is a gentle cutover


Bug fixes from 1.2
------------------
- LineIterator now implements Iterator
  - It was always supposed to...

- FileSystemUtils.freeSpace/freeSpaceKb [IO-83]
  - These should now work on AIX and HP-UX

- FileSystemUtils.freeSpace/freeSpaceKb [IO-90]
  - Avoid infinite looping in Windows
  - Catch more errors with nice messages

- FileSystemUtils.freeSpace [IO-91]
  - This is now documented not to work on SunOS 5

- FileSystemUtils [IO-93]
  - Fixed resource leak leading to 'Too many open files' error
  - Previously did not destroy Process instances (as JDK Javadoc is so poor)
  - http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4801027

- FileUtils.touch [IO-100]
  - The touch method previously gave no indication when the file could not
    be touched successfully (such as due to access restrictions) - it now
    throws an IOException if the last modified date cannot be changed

- FileCleaner
  - This now handles the situation where an error occurs when deleting the file

- IOUtils.copy [IO-84]
  - Copy methods could return inaccurate byte/char count for large streams
  - The copy(InputStream, OutputStream) method now returns -1 if the count is greater than an int
  - The copy(Reader, Writer) method now returns -1 if the count is greater than an int
  - Added a new copyLarge(InputStream, OutputStream) method that returns a long
  - Added a new copyLarge(Reader, Writer) method that returns a long

- CountingInputStream/CountingOutputStream [IO-84]
  - Methods were declared as int thus the count was inaccurate for large streams
  - new long based methods getByteCount()/resetByteCount() added
  - existing methods changed to throw an exception if the count is greater than an int

- FileBasedTestCase
  - Fixed bug in compare content methods identified by GNU classpath

- EndianUtils.writeSwappedLong(byte[], int) [IO-101]
  - An int overrun in the bit shifting when it should have been a long

- EndianUtils.writeSwappedLong(InputStream) [IO-102]
  - The return of input.read(byte[]) was not being checked to ensure all 8 bytes were read

Enhancements from 1.2
---------------------
- DirectoryWalker [IO-86]
  - New class designed for subclassing to walk through a set of files.
    DirectoryWalker provides the walk of the directories, filtering of
    directories and files, and cancellation support. The subclass must provide
    the specific behavior, such as text searching or image processing.

- IOCase
  - New class/enumeration for case-sensitivity control

- FilenameUtils
  - New methods to handle case-sensitivity
  - wildcardMatch - new method that has IOCase as a parameter
  - equals - new method that has IOCase as a parameter

- FileUtils [IO-108] - new default encoding methods for:
  - readFileToString(File)
  - readLines(File)
  - lineIterator(File)
  - writeStringToFile(File, String)
  - writeLines(File, Collection)
  - writeLines(File, Collection, String)

- FileUtils.openOutputStream  [IO-107]
  - new method to open a FileOutputStream, creating parent directories if required
- FileUtils.touch
- FileUtils.copyURLToFile
- FileUtils.writeStringToFile
- FileUtils.writeByteArrayToFile
- FileUtils.writeLines
  - enhanced to create parent directories if required
- FileUtils.openInputStream  [IO-107]
  - new method to open a FileInputStream, providing better error messages than the JDK

- FileUtils.isFileOlder
  - new methods to check if a file is older (i.e. isFileOlder()) - counterparts
    to the existing isFileNewer() methods.

- FileUtils.checksum, FileUtils.checksumCRC32
  - new methods to create a checksum of a file

- FileUtils.copyFileToDirectory  [IO-104]
  - new variant that optionally retains the file date

- FileDeleteStrategy
- FileCleaner    [IO-56,IO-70]
  - FileDeleteStrategy is a strategy for handling file deletion
  - This can be used as a callback in FileCleaner
  - Together these allow FileCleaner to do a forceDelete to kill directories

- FileCleaner.exitWhenFinished [IO-99]
  - A new method that allows the internal cleaner thread to be cleanly terminated

- WildcardFileFilter
  - Replacement for WildcardFilter
  - Accepts both files and directories
  - Ability to control case-sensitivity

- NameFileFilter
  - Ability to control case-sensitivity

- FileFileFilter
  - New IOFileFilter implementation
  - Accepts files where File.isFile() is true
  - In other words it filters out directories
  - Singleton instance provided (FILE)

- CanReadFileFilter
  - New IOFileFilter implementation
  - Accepts files where File.canRead() is true
  - Singleton instances provided (CAN_READ/CANNOT_READ/READ_ONLY)

- CanWriteFileFilter
  - New IOFileFilter implementation
  - Accepts files where File.canWrite() is true
  - Singleton instances provided (CAN_WRITE/CANNOT_WRITE)

- HiddenFileFilter
  - New IOFileFilter implementation
  - Accepts files where File.isHidden() is true
  - Singleton instances provided (HIDDEN/VISIBLE)

- EmptyFileFilter
  - New IOFileFilter implementation
  - Accepts files or directories that are empty
  - Singleton instances provided (EMPTY/NOT_EMPTY)

- TrueFileFilter/FalseFileFilter/DirectoryFileFilter
  - New singleton instance constants (TRUE/FALSE/DIRECTORY)
  - The new constants are more JDK 1.5 friendly with regards to static imports
    (whereas if everything uses INSTANCE, then they just clash)
  - The old INSTANCE constants are still present and have not been deprecated

- FileFilterUtils.sizeRangeFileFilter
  - new sizeRangeFileFilter(long minimumSize, long maximumSize) method which 
    creates a filter that accepts files within the specified size range.

- FileFilterUtils.makeDirectoryOnly/makeFileOnly
  - two new methods that decorate a file filter to make it apply to
    directories only or files only

- NullWriter
  - New writer that acts as a sink for all data, as per /dev/null

- NullInputStream
  - New input stream that emulates a stream of a specified size

- NullReader
  - New reader that emulates a reader of a specified size

- ByteArrayOutputStream  [IO-97]
  - Performance enhancements