code: public static void removeDuplicatesFromOutputDirectory(File outputDirectory,
  			File originDirectory) {
  		if (originDirectory.isDirectory()) {
  			for (String name : originDirectory.list()) {
  				File targetFile = new File(outputDirectory, name);
  				if (targetFile.exists() && targetFile.canWrite()) {
  					if (!targetFile.isDirectory()) {
  						targetFile.delete();
  					}
  					else {
  						FileUtils.removeDuplicatesFromOutputDirectory(targetFile,
  								new File(originDirectory, name));
  					}
  				}
  			}
  		}
  	}
docs: Utility to remove duplicate files from an "output" directory if they already exist
  in an "origin". Recursively scans the origin directory looking for files (not
  directories) that exist in both places and deleting the copy.
  @param outputDirectory the output directory
  @param originDirectory the origin directory