死磕Java多线程（十）------JUC中相关原子操作类的简单使用

1. 常用的JUC下的原子操作类

更新基本类型类：AtomicBoolean，AtomicInteger，AtomicLong

更新数组类：AtomicIntegerArray，AtomicLongArray，AtomicReferenceArray

更新引用类型：AtomicReference，AtomicMarkableReference，AtomicStampedReference

更新字段类： AtomicReferenceFieldUpdater，AtomicIntegerFieldUpdater，AtomicLongFieldUpdater

2. 简单使用

注：详细使用请参照官方文档

2.1 AtomicInteger

import java.util.concurrent.atomic.AtomicInteger;
public class StringTest {    
    /**
     *演示基本类型的原子操作类
     */
   
        static AtomicInteger ai = new AtomicInteger(10);

        public static void main(String[] args) {
            System.out.println(ai.getAndIncrement());
            System.out.println(ai.incrementAndGet());
            System.out.println(ai.addAndGet(24));
        }    
}

结果

10
12
36

2. 2 AtomicIntegerArray

注意：数组value通过构造方法传递进去，然后AtomicIntegerArray会将当前数组复制一份，所以当AtomicIntegerArray对内部的数组元素进行修改时，不会影响传入的数组。

import java.util.concurrent.atomic.AtomicIntegerArray;

/**
 *类说明：
 */
public class UseAtomicIntegerArray {
    static int[] value = new int[] { 1, 2 };
    static AtomicIntegerArray ai = new AtomicIntegerArray(value);
    public static void main(String[] args) {
        ai.getAndSet(0, 3);
        System.out.println(ai.get(0));
        System.out.println(value[0]);//原数组不会变化
    }
}

2.3 AtomicReference

import java.util.concurrent.atomic.AtomicReference;

/**
 *类说明：演示引用类型的原子操作类
 */
public class UseAtomicReference {
    static AtomicReference<UserInfo> atomicUserRef;

    public static void main(String[] args) {
        UserInfo user = new UserInfo("Mark", 15);//要修改的实体的实例
        atomicUserRef = new AtomicReference(user);
        UserInfo updateUser = new UserInfo("Bill",17);
        atomicUserRef.compareAndSet(user,updateUser);

        System.out.println(atomicUserRef.get());
        System.out.println(user);
    }

    //定义一个实体类
    static class UserInfo {
        private volatile String name;
        private int age;
        public UserInfo(String name, int age) {
            this.name = name;
            this.age = age;
        }
        public String getName() {
            return name;
        }
        public int getAge() {
            return age;
        }

        @Override
        public String toString() {
            return "UserInfo{" +
                    "name='" + name + '\'' +
                    ", age=" + age +
                    '}';
        }
    }
}

2.4 AtomicStampedReference

利用版本戳的形式记录了每次改变以后的版本号，这样的话就不会存在ABA问题了。这就是AtomicStampedReference的解决方案。AtomicMarkableReference跟AtomicStampedReference差不多， AtomicStampedReference是使用pair的int stamp作为计数器使用，AtomicMarkableReference的pair使用的是boolean mark。

import java.util.concurrent.atomic.AtomicStampedReference;

/**
 *类说明：演示带版本戳的原子操作类
 */
public class UseAtomicStampedReference {
    static AtomicStampedReference<String> asr
            = new AtomicStampedReference("mark",0);

    public static void main(String[] args) throws InterruptedException {
        //拿到当前的版本号(旧)
        final int oldStamp = asr.getStamp();
        final String oldReference = asr.getReference();
        System.out.println(oldReference+"============"+oldStamp);

        Thread rightStampThread = new Thread(() ->
                System.out.println(Thread.currentThread().getName()+":当前变量值："
                        +oldReference + "-当前版本戳：" + oldStamp + "-"
                        + asr.compareAndSet(oldReference,
                        oldReference + "+Java", oldStamp,
                        oldStamp + 1)));

        Thread errorStampThread = new Thread(() -> {
            String reference = asr.getReference();
            System.out.println(Thread.currentThread().getName()
                    +":当前变量值："
                    +reference + "-当前版本戳：" + asr.getStamp() + "-"
                    + asr.compareAndSet(reference,
                    reference + "+C", oldStamp,
                    oldStamp + 1));
        });
        rightStampThread.start();
        rightStampThread.join();
        errorStampThread.start();
        errorStampThread.join();

        System.out.println(asr.getReference()+"============"+asr.getStamp());
    }
}