public static void orderByLength(String fliePath) {
    List<File> files = Arrays.asList(new File(fliePath).listFiles());
    Collections.sort(files, new Comparator<File>() {
        public int compare(File f1, File f2) {
            long diff = f1.length() - f2.length();
            if (diff > 0)
                return 1;
            else if (diff == 0)
                return 0;
            else
                return -1;
        }

        public boolean equals(Object obj) {
            return true;
        }
    });
    for (File f : files) {
        if (f.isDirectory()) continue;
        System.out.println(f.getName() + ":" + f.length());
    }
}

public static void orderByName(String fliePath) {
    List files = Arrays.asList(new File(fliePath).listFiles());
    Collections.sort(files, new Comparator<File>() {
        @Override
        public int compare(File o1, File o2) {
            if (o1.isDirectory() && o2.isFile())
                return -1;
            if (o1.isFile() && o2.isDirectory())
                return 1;
            return o1.getName().compareTo(o2.getName());
        }
    });
    for (File f : files) {
        System.out.println(f.getName());
    }
}    

public static void orderByDate(String fliePath) {
    File file = new File(fliePath);
    File[] fs = file.listFiles();
    Arrays.sort(fs, new Comparator<File>() {
        public int compare(File f1, File f2) {
            long diff = f1.lastModified() - f2.lastModified();
            if (diff > 0)
                return 1;
            else if (diff == 0)
                return 0;
            else
                return -1;
        }

        public boolean equals(Object obj) {
            return true;
        }

    });
    for (int i = fs.length - 1; i > -1; i--) {
        System.out.println(fs[i].getName());
        System.out.println(new Date(fs[i].lastModified()));
    }
}