static void dumpAll(Path p, String prefix1, String prefix2) {
   synchronized (Path.class) {
     MediaObject obj = p.getObject();
     Log.d(
         TAG,
         prefix1 + p.mSegment + ":" + (obj == null ? "null" : obj.getClass().getSimpleName()));
     if (p.mChildren != null) {
       ArrayList<String> childrenKeys = p.mChildren.keys();
       int i = 0, n = childrenKeys.size();
       for (String key : childrenKeys) {
         Path child = p.mChildren.get(key);
         if (child == null) {
           ++i;
           continue;
         }
         Log.d(TAG, prefix2 + "|");
         if (++i < n) {
           dumpAll(child, prefix2 + "+-- ", prefix2 + "|   ");
         } else {
           dumpAll(child, prefix2 + "+-- ", prefix2 + "    ");
         }
       }
     }
   }
 }
 static void dumpAll() {
   dumpAll(sRoot, "", "");
 }