code: public synchronized void incrCounter(String group, String counter, long amount) {
      getGroup(group).getCounterForName(counter).increment(amount);
    }
docs: Increments the specified counter by the specified amount, creating it if
  it didn't already exist.
  @param group the name of the group
  @param counter the internal name of the counter
  @param amount amount by which counter is to be incremented