Java线程：并发协作-死锁

分手后的思念是犯贱 2022-08-24 01:56 170阅读 0赞

Java线程：并发协作-死锁

线程发生死锁可能性很小，即使看似可能发生死锁的代码，在运行时发生死锁的可能性也是小之又小。

发生死锁的原因一般是两个对象的锁相互等待造成的。

在《Java线程：线程的同步与锁》一文中，简述死锁的概念与简单例子，但是所给的例子是不完整的，这里给出一个完整的例子。

/\*\*  
\* Java线程：并发协作-死锁  
\*  
\* @author Administrator 2009-11-4 22:06:13  
\*/  
public class Test \{  
        public static void main(String\[\] args) \{  
                DeadlockRisk dead = new DeadlockRisk();  
                MyThread t1 = new MyThread(dead, 1, 2);  
                MyThread t2 = new MyThread(dead, 3, 4);  
                MyThread t3 = new MyThread(dead, 5, 6);  
                MyThread t4 = new MyThread(dead, 7, 8);  
  
                t1.start();  
                t2.start();  
                t3.start();  
                t4.start();  
        \}  
  
\}  
  
class MyThread extends Thread \{  
        private DeadlockRisk dead;  
        private int a, b;  
  
  
        MyThread(DeadlockRisk dead, int a,  int b) \{  
                this.dead = dead;  
                this.a = a;  
                this.b = b;  
        \}  
  
        @Override  
        public void run() \{  
                dead.read();  
                dead.write(a, b);  
        \}  
\}  
  
class DeadlockRisk \{  
        private static class Resource \{  
                public  int value;  
        \}  
  
        private Resource resourceA =  new Resource();  
        private Resource resourceB =  new Resource();  
  
        public int read() \{  
                synchronized (resourceA) \{  
                        System.out.println("read():" \+ Thread.currentThread().getName() + "获取了resourceA的锁！");  
                        synchronized (resourceB) \{  
                                System.out.println("read():" \+ Thread.currentThread().getName() + "获取了resourceB的锁！");  
                                return resourceB.value + resourceA.value;  
                        \}  
                \}  
        \}  
  
        public void write(int a, int b) \{  
                synchronized (resourceB) \{  
                        System.out.println("write():" \+ Thread.currentThread().getName() + "获取了resourceA的锁！");  
                        synchronized (resourceA) \{  
                                System.out.println("write():" \+ Thread.currentThread().getName() + "获取了resourceB的锁！");  
                                resourceA.value = a;  
                                resourceB.value = b;  
                        \}  
                \}  
        \}  
\}

下面死锁的情况发生了，真是难得一见啊：

![200911041257345567687.png][]

本文出自 “[熔  岩][Link 1]” 博客，请务必保留此出处[http://lavasoft.blog.51cto.com/62575/222074][http_lavasoft.blog.51cto.com_62575_222074]

[200911041257345567687.png]: /images/20220823/b1833014afe144b3a15c2b460dabb45d.png
[Link 1]: http://lavasoft.blog.51cto.com/
[http_lavasoft.blog.51cto.com_62575_222074]: http://lavasoft.blog.51cto.com/62575/222074