/** * Gets the extension of a filename. This method returns the textual part of the filename after the last dot. There must be no directory separator after * the dot. * <pre> * foo.txt --> "txt" * a/b/c.jpg --> "jpg" * a/b.txt/c --> "" * a/b/c --> "" * </pre> * The output will be the same irrespective of the machine that the code is running on. * * @param filename the filename to retrieve the extension of. * @return the extension of the file or an empty string if none exists. */ public static String getExtension(String filename) { if (filename == null) { return null; } int index = indexOfExtension(filename); if (index == -1) { return ""; } else { return filename.substring(index + 1); } }