ABA问题解决

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mb5fdb0f4aaf587 2021-08-06 18:15:00

文章标签 Java 复用 java 包装类 java开发 文章分类 Java 后端开发

什么是ABA问题？

解决方案：引入原子引用，AtomicStampedReference

import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicStampedReference;


public class AtomicReferenceDemo {
    public static void main(String[] args) {
        AtomicStampedReference<Integer> atomic = new AtomicStampedReference<Integer>(1, 1);
        new Thread(()->{
            int stamp = atomic.getStamp();
            System.out.println("a1=>" + stamp);

            //延时2秒，保证A,线程进来后取得的版本号一致
            try {
                TimeUnit.SECONDS.sleep(1);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            System.out.println("A------");
            System.out.println(atomic.compareAndSet(1, 2, atomic.getStamp(), atomic.getStamp() + 1));
            System.out.println("a2=>" + atomic.getStamp());

            System.out.println("A------");
            System.out.println(atomic.compareAndSet(2, 1, atomic.getStamp(), atomic.getStamp() + 1));
            System.out.println("a3=>" + atomic.getStamp());

        }, "a").start();



        new Thread(()->{
            int stamp = atomic.getStamp();
            System.out.println("b1=>" + stamp);

            try {
                TimeUnit.SECONDS.sleep(2);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            System.out.println("B------");
            System.out.println(atomic.compareAndSet(1, 6, stamp, stamp + 1));
            System.out.println("b2=>" + atomic.getStamp());

        }, "b").start();
    }
}

这里需要注意的是，对于包装类Integer有个大坑，详见阿里巴巴java开发手册：