List files by extension - empty directory

Script

class FileExtFilter implements FileFilter {

	public FileExtFilter(String ext) {
		this.ext = ext;
	}

	public boolean accept(File file) {
		return file.getName().endsWith(ext);
	}

	String ext = null;
}

if (extension == void || extension.equals("")) {
	throw new RuntimeException(
			"The 'extension' parameter cannot be null.  Please enter a valid file extension.");
}

if (directory == void || directory.equals("")) {
	throw new RuntimeException(
			"The 'directory' parameter cannot be null.  Please enter a valid file directory.");
}

File dirObj = new File(directory);

if (!dirObj.exists()) {
	throw new RuntimeException("The 'directory' parameter specified:" + directory
			+ "does not exist.  Please enter a valid file directory.");
}

File[] fileObjList = dirObj.listFiles(new FileExtFilter(extension));
List filelist = new ArrayList();
for (int i = 0; i < fileObjList.length; i++) {
	filelist.add(fileObjList[i].getAbsolutePath());
}

Script

File temp = File.createTempFile("taverna", ".dir");
temp.delete();
temp.mkdir();
temp.deleteOnExit();
directoryPath = temp.getCanonicalPath();

Value