java并发AtomicReference

AtomicReference的作用

已经介绍过AtomicInteger,AtomicIntegerArray，AtomicReference是针对对象的。

他通过CAS和volatile保证了对象操作的原子性和可见性，既然是引用，就会造成引用对象的变化。

public AtomicReference(V initialValue) {        value = initialValue;    }

如果value改变了对象的属性，initialValue的属性也会改变

CAS函数的实现

/**     * Atomically sets the value to the given updated value     * if the current value {@code ==} the expected value.     * @param expect the expected value     * @param update the new value     * @return {@code true} if successful. False return indicates that     * the actual value was not equal to the expected value.     */    public final boolean compareAndSet(V expect, V update) {        return unsafe.compareAndSwapObject(this, valueOffset, expect, update);    }

例子

package javalearn.javabase.thread.atomic;import lombok.AllArgsConstructor;import lombok.Data;import lombok.ToString;import lombok.extern.slf4j.Slf4j;import java.util.concurrent.atomic.AtomicReference;@Slf4jpublic class AtomicReferanceTest {    public static void main(String[] args) {        Persion p1 = new Persion("jack", 1);        Persion p2 = new Persion("linda", 2);        Persion p3 = new Persion("tony", 3);        log.info("persion 3 :{}",p3.toString());        AtomicReference
    
      atomicReference =new AtomicReference(p3);        log.info("AtomicReference is :{}",atomicReference.toString());        atomicReference.compareAndSet(p3,p1);        log.info("AtomicReference is :{}",atomicReference.toString());        log.info("persion 3 :{}",p3.toString());        atomicReference.set(p2);        log.info("AtomicReference is :{}",atomicReference.toString());        log.info("persion 3 :{}",p3.toString());        atomicReference.get().setId(33);        log.info("AtomicReference is :{}",atomicReference.toString());        log.info("AtomicReference is :{}",atomicReference.toString());        log.info("persion 3 :{}",p3.toString());        log.info("persion 2 :{}",p2.toString());    }    @AllArgsConstructor    @Data    @ToString    static class Persion {        private String name;        private int id;    }}
    

结果

13:34:22.313 [main] INFO javalearn.javabase.thread.atomic.AtomicReferanceTest - persion 3 :AtomicReferanceTest.Persion(name=tony, id=3)13:34:22.321 [main] INFO javalearn.javabase.thread.atomic.AtomicReferanceTest - AtomicReference is :AtomicReferanceTest.Persion(name=tony, id=3)13:34:22.321 [main] INFO javalearn.javabase.thread.atomic.AtomicReferanceTest - AtomicReference is :AtomicReferanceTest.Persion(name=jack, id=1)13:34:22.321 [main] INFO javalearn.javabase.thread.atomic.AtomicReferanceTest - persion 3 :AtomicReferanceTest.Persion(name=tony, id=3)13:34:22.321 [main] INFO javalearn.javabase.thread.atomic.AtomicReferanceTest - AtomicReference is :AtomicReferanceTest.Persion(name=linda, id=2)13:34:22.321 [main] INFO javalearn.javabase.thread.atomic.AtomicReferanceTest - persion 3 :AtomicReferanceTest.Persion(name=tony, id=3)13:34:22.321 [main] INFO javalearn.javabase.thread.atomic.AtomicReferanceTest - AtomicReference is :AtomicReferanceTest.Persion(name=linda, id=33)13:34:22.321 [main] INFO javalearn.javabase.thread.atomic.AtomicReferanceTest - AtomicReference is :AtomicReferanceTest.Persion(name=linda, id=33)13:34:22.321 [main] INFO javalearn.javabase.thread.atomic.AtomicReferanceTest - persion 3 :AtomicReferanceTest.Persion(name=tony, id=3)13:34:22.321 [main] INFO javalearn.javabase.thread.atomic.AtomicReferanceTest - persion 2 :AtomicReferanceTest.Persion(name=linda, id=33)