code: public synchronized void incrAllCounters(Counters other) {
      for (Group otherGroup: other) {
        Group group = getGroup(otherGroup.getName());
        group.displayName = otherGroup.displayName;
        for (Counter otherCounter : otherGroup) {
          Counter counter = group.getCounterForName(otherCounter.getName());
          counter.setDisplayName(otherCounter.getDisplayName());
          counter.increment(otherCounter.getValue());
        }
      }
    }
docs: Increments multiple counters by their amounts in another Counters
  instance.
  @param other the other Counters instance