public class AtomicCounterTest {
	private static final int N_THREADS = 100;
	private static final int INCREMENT = 1_000_000;
	private static void incCounter(AtomicCounter atomicCounter) {
		for (int i= 0; i < INCREMENT; ++i) {
			atomicCounter.updateAndGet(x -> x+1);
		}
	}
	public static void main(String[] args) {
		AtomicCounter atomicCounter = new AtomicCounter();
		Thread[] threads = new Thread[N_THREADS];
		for (int i = 0; i < N_THREADS; ++i) {
			Thread incrementer = new Thread(()-> incCounter(atomicCounter));
			incrementer.start();
			threads[i] = incrementer;
		}
		for (Thread incrementer: threads) {
			try {
				incrementer.join();
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
		System.out.println("Counter value = " + 
		               		atomicCounter.updateAndGet(x -> x)  + // only to get, not to change
							" and that is" + 
		               		(atomicCounter.updateAndGet(x -> x) == N_THREADS * INCREMENT ? "" : "NOT") + 
		               		" correct.");
	}
}