code: public static boolean changeFilenameSuffix(final File file, final String newSuffix,
  		final boolean delete)
  		throws IOException, FileDoesNotExistException, FileIsADirectoryException
  	{
  		if (!file.exists())
  		{
  			final String error = "The " + file + " does not exists.";
  			throw new FileDoesNotExistException(error);
  		}
  		final String fileNamePrefix = FileExtensions.getFilenamePrefix(file);
  		final String newFilename = fileNamePrefix + newSuffix;
  		final File file2 = new File(newFilename);
  		final boolean success = RenameFileExtensions.renameFile(file, file2, delete);
  		return success;
  	}
docs: Changes the suffix from the Filename. Example: test.dat to test.xxx
  
  @param file
  The file to change.
  @param newSuffix
  The new suffix. You must start with a dot. For instance: .xxx
  @param delete
  If its true than its deletes the existing file with the same name. But before it
  copys the contents into the new File.
  @return true, if change filename suffix
  @throws IOException
  Signals that an I/O exception has occurred.
  @throws FileDoesNotExistException
  If the file does not exist.
  @throws FileIsADirectoryException
  the file is A directory exception