protected AtomicLong createCounter(String counterName) {
    AtomicLong c = new AtomicLong(0);
    counters.put(counterName, c);
    return c;
  }
Create a new counter with the specified name
@return {@link AtomicLong} instance for the counter with counterName
hbase-client/src/main/java/org/apache/hadoop/hbase/client/metrics/ServerSideScanMetrics.java