Java线程：并发协作-死锁

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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：

这里写图片描述

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