java-15种锁之自旋锁_java自旋锁有哪些

1、Java自旋锁理论

自旋锁（spinlock）：是指尝试去获取锁的线程不会立即阻塞，而是采用循环的方式去获取锁，这样的好处是减少线程上下文切换消耗，缺点是循环会消耗CPU。   （等待的时候还可以去处理其他任务）

 public final int getAndAddInt(Object var1, long var2, int var4) {
 
        int var5;
 
        do {
 
            var5 = this.getIntVolatile(var1, var2);
 
        } while(!this.compareAndSwapInt(var1, var2, var5, var5 + var4));
 
 
 
        return var5;
 
}

2、手写自旋锁

public class SpinlockDemo {
 
       // AtomicReference对象创建初始值为null
 
    private AtomicReference<Thread> threadAtomicReference = new AtomicReference<>();
 
 
 
    public void lock() {
 
        Thread currentThread  = Thread.currentThread();
 
              // 模拟自旋
 
        while(!threadAtomicReference.compareAndSet(null,currentThread)) {
 
 
 
        }
 
        System.out.println(Thread.currentThread().getName()+"\t get lock");
 
    }
 
 
 
    public void unLock(){
 
        Thread currentThread  = Thread.currentThread();
 
        threadAtomicReference.compareAndSet(currentThread,null);
 
        System.out.println(Thread.currentThread().getName()+"\t release lock");
 
    }
 
 
 
    public static void main(String[] args) {
 
        SpinlockDemo spinlockDemo = new SpinlockDemo();
 
        // T1线程使用自旋方式获取锁，然后模拟5s业务处理
 
        new Thread(()-> {
 
            spinlockDemo.lock();
 
            try {
 
                System.out.println(Thread.currentThread().getName()+"\t开始模拟5s业务处理");
 
                TimeUnit.SECONDS.sleep(5);
 
                System.out.println(Thread.currentThread().getName()+"\t模拟5s业务处理完毕");
 
            } catch (InterruptedException e) {
 
                e.printStackTrace();
 
            }
 
            spinlockDemo.unLock();
 
        },"T1").start();
 
 
 
        // T1线程使用自旋方式获取锁，然后模拟3s业务处理
 
        new Thread(()-> {
 
            spinlockDemo.lock();
 
            try {
 
                System.out.println(Thread.currentThread().getName()+"\t开始模拟5s业务处理");
 
                TimeUnit.SECONDS.sleep(5);
 
                System.out.println(Thread.currentThread().getName()+"\t模拟5s业务处理完毕");
 
            } catch (InterruptedException e) {
 
                e.printStackTrace();
 
            }
 
            spinlockDemo.unLock();
 
        },"T2").start();
 
    }
 
}