code: private static String list(String[] arr, int from, int len) {
  	StringBuffer sb = new StringBuffer();
  	for (int i = from; i < len; i++) {
  	    sb.append(arr[i]);
  	    if (i + 1 != arr.length) sb.append('/');
  	}
  	return sb.toString();
      }
docs: convert a String array to a string list, but only part of it
  
  @param arr String Array
  @param from start from here
  @param len how many element
  @return String list