Java多线程22 Atomic

public class Sync01 implements Runnable {
    static AtomicInteger i = new AtomicInteger();

    public static void main(String[] args) throws InterruptedException {
        Sync01 sync01 = new Sync01();
        Sync01 sync02 = new Sync01();

        Thread thread = new Thread(sync01);
        Thread thread2 = new Thread(sync02);

        thread.start();
        thread2.start();

        thread.join();
        thread2.join();

        System.out.println(i);
    }

    @Override
    public void run() {
        add();
    }

    private void add() {
        synchronized (this) {
            for (int j = 0; j < 10000; j++) {
                i.incrementAndGet();
            }
        }
    }
}

public class AtomicBooleanExample {

    AtomicBoolean atomicBoolean = new AtomicBoolean(false);

    public void shutDown() {
        atomicBoolean.compareAndSet(false,true);
    }

    public void doWork() {
        while (!atomicBoolean.get()) {
        }
        System.out.println("你能读到我们...");
    }

    public static void main(String[] args) throws InterruptedException {
        AtomicBooleanExample volatile01 = new AtomicBooleanExample();
        new Thread(() -> {
            volatile01.doWork();
        }).start();

        Thread.sleep(2000);

        new Thread(() -> {
            volatile01.shutDown();
        }).start();
    }
}

ABA问题

public class AtomicIntegerABAExample {

    private static AtomicInteger atomicInt = new AtomicInteger(100);

    public static void main(String[] args) throws InterruptedException {
        Thread intT1 = new Thread(new Runnable() {
            @Override
            public void run() {
                atomicInt.compareAndSet(100, 101);
                atomicInt.compareAndSet(101, 100);
            }
        });
        Thread intT2 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    TimeUnit.SECONDS.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                boolean c3 = atomicInt.compareAndSet(100, 101);
                System.out.println(c3);
            }
        });
        intT1.start();
        intT2.start();
        intT1.join();
        intT2.join();
    }
}

输出true

解决 添加版本号

public class AtomicStampedReferenceABAExample {


    private static AtomicStampedReference atomicStampedRef = new AtomicStampedReference(100, 0);

    public static void main(String[] args) throws InterruptedException {
        Thread intT1 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    TimeUnit.SECONDS.sleep(1);
                } catch (InterruptedException e) {
                }
                atomicStampedRef.compareAndSet(100, 101, atomicStampedRef.getStamp(), atomicStampedRef.getStamp() + 1);
                atomicStampedRef.compareAndSet(101, 100, atomicStampedRef.getStamp(), atomicStampedRef.getStamp() + 1);
            }
        });
        Thread intT2 = new Thread(new Runnable() {
            @Override
            public void run() {

                int stamp = atomicStampedRef.getStamp();

                try {
                    TimeUnit.SECONDS.sleep(2);
                } catch (InterruptedException e) {
                }
                boolean c3 = atomicStampedRef.compareAndSet(100, 101,stamp,stamp+1);
                System.out.println(c3);
            }
        });
        intT1.start();
        intT2.start();
        intT1.join();
        intT2.join();
    }
}