Java鎖之自旋鎖

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目錄

java鎖之自旋鎖理論知識

java鎖之自旋鎖代碼驗證

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1. java鎖之自旋鎖理論知識

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自旋鎖是指嘗試獲取鎖的線程不會立即阻塞，而是采用循環的方式去嘗試獲取鎖，這樣的好處是減少線程上下文切換的消耗，缺
點是循環會消耗CPU

2. java鎖之自旋鎖代碼驗證

代碼驗證：通過CAS操作完成自旋鎖，A線程先進來調用myLock方法自己持有鎖5秒鐘，B隨后進來后發現當前有線程持有鎖，不是null，所以只能通過自旋等待，知道A釋放鎖后B隨后搶到。

import java.util.concurrent.TimeUnit; import java.util.concurrent.atomic.AtomicReference;public class SpinLockDemo {//原子引用線程AtomicReference<Thread> atomicReference = new AtomicReference<>();public void myLock(){Thread thread = Thread.currentThread();System.out.println(Thread.currentThread().getName()+"\t come in ");while (!atomicReference.compareAndSet(null,thread)){}}public void myUnlock(){Thread thread = Thread.currentThread();atomicReference.compareAndSet(thread,null);System.out.println(Thread.currentThread().getName()+"\t invoked myUnlock()");}public static void main(String[] args) {SpinLockDemo spinLockDemo = new SpinLockDemo();new Thread(() -> {spinLockDemo.myLock();try {TimeUnit.SECONDS.sleep(5);} catch (InterruptedException e) {e.printStackTrace();}spinLockDemo.myUnlock();},"AA").start();try {TimeUnit.SECONDS.sleep(1);} catch (InterruptedException e) {e.printStackTrace();}new Thread(() -> {spinLockDemo.myLock();try {TimeUnit.SECONDS.sleep(1);} catch (InterruptedException e) {e.printStackTrace();}spinLockDemo.myUnlock();},"BB").start();} }

編譯結果：

總結

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