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java中可重入锁和自旋锁

时间:2018-04-17 00:03:20      阅读:54      评论:0      收藏:0      [点我收藏+]

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1、可重入锁:

也称为递归锁,当外层函数获得该锁之后,内层递归函数仍有获取该锁的代码,结果不受影响;

java中的synchronized  ReentrantLock都是可重的

举例:

public class Test implements Runnable{

    public synchronized void get(){
        System.out.println(Thread.currentThread().getId());
        set();
    }

    public synchronized void set(){
        System.out.println(Thread.currentThread().getId());
    }

    @Override
    public void run() {
        get();
    }
    public static void main(String[] args) {
        Test ss=new Test();
        new Thread(ss).start();
        new Thread(ss).start();
        new Thread(ss).start();
    }
}



public class Test implements Runnable {
    ReentrantLock lock = new ReentrantLock();

    public void get() {
        lock.lock();
        System.out.println(Thread.currentThread().getId());
        set();
        lock.unlock();
    }

    public void set() {
        lock.lock();
        System.out.println(Thread.currentThread().getId());
        lock.unlock();
    }

    @Override
    public void run() {
        get();
    }

    public static void main(String[] args) {
        Test ss = new Test();
        new Thread(ss).start();
        new Thread(ss).start();
        new Thread(ss).start();
    }
}

 

2、自旋锁

一个线程直接循环执行一个任务,不触发临界条件,另一个线程控制临界条件,另一个线程执行时可以使前一个线程停止执行。

例子:

public class SpinLock {

  private AtomicReference<Thread> sign =new AtomicReference<>();

  public void lock(){
    Thread current = Thread.currentThread();
    while(!sign .compareAndSet(null, current)){
    }
  }

  public void unlock (){
    Thread current = Thread.currentThread();
    sign .compareAndSet(current, null);
  }
}

  

 

 

public class Test implements Runnable{
02  
03     public synchronized void get(){
04         System.out.println(Thread.currentThread().getId());
05         set();
06     }
07  
08     public synchronized void set(){
09         System.out.println(Thread.currentThread().getId());
10     }
11  
12     @Override
13     public void run() {
14         get();
15     }
16     public static void main(String[] args) {
17         Test ss=new Test();
18         new Thread(ss).start();
19         new Thread(ss).start();
20         new Thread(ss).start();
21     }
22 }
01 public class Test implements Runnable {
02     ReentrantLock lock = new ReentrantLock();
03  
04     public void get() {
05         lock.lock();
06         System.out.println(Thread.currentThread().getId());
07         set();
08         lock.unlock();
09     }
10  
11     public void set() {
12         lock.lock();
13         System.out.println(Thread.currentThread().getId());
14         lock.unlock();
15     }
16  
17     @Override
18     public void run() {
19         get();
20     }
21  
22     public static void main(String[] args) {
23         Test ss = new Test();
24         new Thread(ss).start();
25         new Thread(ss).start();
26         new Thread(ss).start();
27     }
28 }

java中可重入锁和自旋锁

标签:content   执行   ola   ati   top   over   rect   ons   可重入锁   

原文地址:https://www.cnblogs.com/hy87/p/8859021.html

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