Extract the extension of a file from a full pathname

public static String getFileExtension(String fileName) {
        File tmpFile = new File(fileName);
        tmpFile.getName();
        int whereDot = tmpFile.getName().lastIndexOf('.');
        if (0 < whereDot && whereDot <= tmpFile.getName().length() - 2 ) {
            return tmpFile.getName().substring(whereDot+1);
        }    
        return "";
    }