CAS

{
    static AtomicInteger atomicInteger = new AtomicInteger(100);
    static AtomicStampedReference<Integer> stampedReference = new AtomicStampedReference<>(100,1);

    public static void main(String[] args)
    {
        new Thread(() -> {
            int stamp = stampedReference.getStamp();
            System.out.println(Thread.currentThread().getName()+"\t"+"首次版本号："+stamp);

            //暂停500毫秒,保证后面的t4线程初始化拿到的版本号和我一样
            try { TimeUnit.MILLISECONDS.sleep(500); } catch (InterruptedException e) { e.printStackTrace(); }

            stampedReference.compareAndSet(100,101,stampedReference.getStamp(),stampedReference.getStamp()+1);
            System.out.println(Thread.currentThread().getName()+"\t"+"2次流水号："+stampedReference.getStamp());

            stampedReference.compareAndSet(101,100,stampedReference.getStamp(),stampedReference.getStamp()+1);
            System.out.println(Thread.currentThread().getName()+"\t"+"3次流水号："+stampedReference.getStamp());

        },"t3").start();

        new Thread(() -> {
            int stamp = stampedReference.getStamp();
            System.out.println(Thread.currentThread().getName()+"\t"+"首次版本号："+stamp);

            //暂停1秒钟线程,等待上面的t3线程，发生了ABA问题
            try { TimeUnit.SECONDS.sleep(1); } catch (InterruptedException e) { e.printStackTrace(); }

            boolean b = stampedReference.compareAndSet(100, 2022, stamp, stamp + 1);

            System.out.println(b+"\t"+stampedReference.getReference()+"\t"+stampedReference.getStamp());

        },"t4").start();

    }

    private static void abaHappen()
    {
        new Thread(() -> {
            atomicInteger.compareAndSet(100,101);
            try { TimeUnit.MILLISECONDS.sleep(10); } catch (InterruptedException e) { e.printStackTrace(); }
            atomicInteger.compareAndSet(101,100);
        },"t1").start();

        new Thread(() -> {
            try { TimeUnit.MILLISECONDS.sleep(200); } catch (InterruptedException e) { e.printStackTrace(); }
            System.out.println(atomicInteger.compareAndSet(100, 2022)+"\t"+atomicInteger.get());
        },"t2").start();
    }
}

@Getter
@ToString
@AllArgsConstructor
class User
{
    String userName;
    int    age;
}


public class AtomicReferenceDemo
{
    public static void main(String[] args)
    {
        AtomicReference<User> atomicReference = new AtomicReference<>();

        User z3 = new User("z3",22);
        User li4 = new User("li4",28);

        atomicReference.set(z3);

        System.out.println(atomicReference.compareAndSet(z3, li4)+"\t"+atomicReference.get().toString());
        System.out.println(atomicReference.compareAndSet(z3, li4)+"\t"+atomicReference.get().toString());


    }
}

@NoArgsConstructor
@AllArgsConstructor
@Data
class Book
{
    private int id;
    private String bookName;
}

public class AtomicStampedDemo
{
    public static void main(String[] args)
    {
        Book javaBook = new Book(1,"javaBook");

        AtomicStampedReference<Book> stampedReference = new AtomicStampedReference<>(javaBook,1);

        System.out.println(stampedReference.getReference()+"\t"+stampedReference.getStamp());

        Book mysqlBook = new Book(2,"mysqlBook");

        boolean b;
        b = stampedReference.compareAndSet(javaBook, mysqlBook, stampedReference.getStamp(), stampedReference.getStamp() + 1);

        System.out.println(b+"\t"+stampedReference.getReference()+"\t"+stampedReference.getStamp());


        b = stampedReference.compareAndSet(mysqlBook, javaBook, stampedReference.getStamp(), stampedReference.getStamp() + 1);

        System.out.println(b+"\t"+stampedReference.getReference()+"\t"+stampedReference.getStamp());

    }
}

{
    public static void main(String[] args)
    {
        AtomicInteger atomicInteger = new AtomicInteger(5);

        System.out.println(atomicInteger.compareAndSet(5, 2022)+"\t"+atomicInteger.get());
        System.out.println(atomicInteger.compareAndSet(5, 2022)+"\t"+atomicInteger.get());

        atomicInteger.getAndIncrement();
    }
}

/**
 * 题目：实现一个自旋锁,复习CAS思想
 * 自旋锁好处：循环比较获取没有类似wait的阻塞。
 *
 * 通过CAS操作完成自旋锁，A线程先进来调用myLock方法自己持有锁5秒钟，B随后进来后发现
 * 当前有线程持有锁，所以只能通过自旋等待，直到A释放锁后B随后抢到。
 */
public class SpinLockDemo
{
    AtomicReference<Thread> atomicReference = new AtomicReference<>();

    public void lock()
    {
        Thread thread = Thread.currentThread();
        System.out.println(Thread.currentThread().getName()+"\t"+"----come in");
        while (!atomicReference.compareAndSet(null, thread)) {

        }
    }

    public void unLock()
    {
        Thread thread = Thread.currentThread();
        atomicReference.compareAndSet(thread,null);
        System.out.println(Thread.currentThread().getName()+"\t"+"----task over,unLock...");
    }

    public static void main(String[] args)
    {
        SpinLockDemo spinLockDemo = new SpinLockDemo();

        new Thread(() -> {
            spinLockDemo.lock();
            //暂停几秒钟线程
            try { TimeUnit.SECONDS.sleep(5); } catch (InterruptedException e) { e.printStackTrace(); }
            spinLockDemo.unLock();
        },"A").start();

        //暂停500毫秒,线程A先于B启动
        try { TimeUnit.MILLISECONDS.sleep(500); } catch (InterruptedException e) { e.printStackTrace(); }

        new Thread(() -> {
            spinLockDemo.lock();

            spinLockDemo.unLock();
        },"B").start();


    }
}