Hello World Atomic

TestCounter.java

package cun;

import java.util.concurrent.atomic.AtomicInteger;

public class TestCounter {

    public static void main(String[] args) {
        ExecutorService executors = Executors.newCachedThreadPool();

        Counter counter = new Counter();
        executors.submit(new TestThread(counter, "thread1"));
        executors.submit(new TestThread(counter, "thread2"));
        executors.submit(new TestThread(counter, "thread3"));
        executors.submit(new TestThread(counter, "thread4"));
        executors.submit(new TestThread(counter, "thread5"));
    }

    static class TestThread implements Runnable {
        Counter counter;
        String name;

        public TestThread(Counter counter, String name) {
            this.counter = counter;
            this.name = name;
        }


        @Override
        public void run() {
            for (int i = 1; i < 3; i++) {
                System.out.println(name + ": " + counter.increment());
            }
        }
    }

    static class Counter {
        AtomicInteger i = new AtomicInteger();

        int increment() {
            int old;
            int newResult;

            do {
                old = i.get();
                try {
                    Thread.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                newResult = old + 1;
            }
            while (!i.compareAndSet(old, newResult));

            return newResult;
        }
    }
}

output
thread2: 1
thread1: 2
thread1: 3
thread4: 4
thread2: 5
thread4: 6
thread3: 7
thread3: 8
thread5: 9
thread5: 10