case '1':
long val=counter.incrementAndGet();
System.out.println("counter: " + val);
break;
case '2':
val=counter.decrementAndGet();
System.out.println("counter: " + val);
break;
case '3':
long expect=Util.readLongFromStdin("expected value: ");
long update=Util.readLongFromStdin("update: ");