Pit encountered by handwritten ABA

AtomicStampedReference<Integer> stampedReference = new AtomicStampedReference<>(100, 1);

Thread t1 = new Thread(()->{
    boolean b = stampedReference.compareAndSet(100, 200, stampedReference.getStamp(), stampedReference.getStamp()+1);
    System.out.println("t1           "+b);
    try {
        TimeUnit.SECONDS.sleep(5);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    boolean b1 = stampedReference.compareAndSet(200, 100, stampedReference.getStamp(), stampedReference.getStamp()+1);
    System.out.println("t1           "+b1+"  "+ stampedReference.getReference()+" "+stampedReference.getStamp());
},"t1");
t1.start();

Thread t2 = new Thread(()->{
    System.out.println(stampedReference.getReference()+"   "+stampedReference.getStamp());
    boolean b = stampedReference.compareAndSet(200, 300, stampedReference.getStamp(), stampedReference.getStamp()+1);
    System.out.println("t2           "+b);
    boolean c = stampedReference.compareAndSet(300, 200, stampedReference.getStamp(), stampedReference.getStamp()+1);
    System.out.println("t2           "+c);
},"t2");
t2.start();

Running results ：

  I found out A Thread switching back failed ： At last, I got the idea ,Integer exceed 128 Meeting new, Instead of taking it from the cache , So it will fail .

Change to less than 128 Value , Observations ：

Thread t1 = new Thread(()->{
    boolean b = stampedReference.compareAndSet(100, 105, stampedReference.getStamp(), stampedReference.getStamp()+1);
    System.out.println("t1           "+b);
    try {
        TimeUnit.SECONDS.sleep(5);
    } catch (InterruptedException e) {
        e.printStackTrace();
    }
    boolean b1 = stampedReference.compareAndSet(105, 100, stampedReference.getStamp(), stampedReference.getStamp()+1);
    System.out.println("t1           "+b1+"  "+ stampedReference.getReference()+" "+stampedReference.getStamp());
},"t1");
t1.start();

Thread t2 = new Thread(()->{
    System.out.println(stampedReference.getReference()+"   "+stampedReference.getStamp());
    boolean b = stampedReference.compareAndSet(105, 104, stampedReference.getStamp(), stampedReference.getStamp()+1);
    System.out.println("t2           "+b);
    boolean c = stampedReference.compareAndSet(104, 105, stampedReference.getStamp(), stampedReference.getStamp()+1);
    System.out.println("t2           "+c);
},"t2");
t2.start();

  Find out aba The result was as successful as expected . You use Integer Be sure to note that the scope cannot exceed 128, Otherwise new object , Naturally, two objects are not the same .