如何解决ABA问题
使用AtomicStampedReference版本原子引用类可以解决ABA问题
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.AtomicStampedReference;
public class AtomicStampedReferenceDemo {
public static void main(String[] args) {
AtomicReference<Integer> atomicReference = new AtomicReference<>(100);
System.out.println("=============ABA问题产生=============");
new Thread(() -> {
System.out.println(Thread.currentThread().getName() + "\t" + atomicReference.compareAndSet(100, 101) + "\t" + atomicReference.get());
System.out.println(Thread.currentThread().getName() + "\t" + atomicReference.compareAndSet(101, 100) + "\t" + atomicReference.get());
}, "T1").start();
new Thread(() -> {
// 先让T1线程执行
try {
TimeUnit.SECONDS.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + "\t" + atomicReference.compareAndSet(100, 2019) + "\t" + atomicReference.get());
}, "T2").start();
// ABA问题解决
AtomicStampedReference<Integer> atomicStampedReference = new AtomicStampedReference<>(100, 1);
new Thread(() -> {
int stamp = atomicStampedReference.getStamp();
// 暂停2秒，等待T2线程执行完毕
try {
TimeUnit.SECONDS.sleep(2);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("=============ABA问题解决=============");
System.out.println(Thread.currentThread().getName() + "\t第一次版本号：" + stamp + "\t" + atomicStampedReference.compareAndSet(100, 101, stamp, atomicStampedReference.getStamp() + 1));
System.out.println(Thread.currentThread().getName() + "\t第二次版本号：" + atomicStampedReference.getStamp() + "\t" + atomicStampedReference.compareAndSet(101, 100, atomicStampedReference.getStamp(), atomicStampedReference.getStamp() + 1));
}, "T3").start();
new Thread(() -> {
int stamp = atomicStampedReference.getStamp();
// 暂停3秒，等待T3线程执行完毕
try {
TimeUnit.SECONDS.sleep(3);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(Thread.currentThread().getName() + "\t第三次版本号：" + atomicStampedReference.getStamp() + "\t当前实际值：" + atomicStampedReference.getReference() + "\t" + atomicStampedReference.compareAndSet(100, 2019, stamp, atomicStampedReference.getStamp() + 1));
}, "T4").start();
}
}
程序执行结果如下：
