@Override
 public int compare(FolderInfo lhs, FolderInfo rhs) {
   if (lhs.getNumOfTracks() > rhs.getNumOfTracks()) {
     return -1;
   } else if (lhs.getNumOfTracks() < rhs.getNumOfTracks()) {
     return 1;
   } else {
     return 0;
   }
 }