code: public static long getDU(File dir) {
      long size = 0;
      if (!dir.exists())
        return 0;
      if (!dir.isDirectory()) {
        return dir.length();
      } else {
        size = dir.length();
        File[] allFiles = dir.listFiles();
        for (int i = 0; i < allFiles.length; i++) {
          size = size + getDU(allFiles[i]);
        }
        return size;
      }
    }
docs: Takes an input dir and returns the du on that local directory. Very basic
  implementation.
  
  @param dir
  The input dir to get the disk space of this local dir
  @return The total disk space of the input local directory