死鎖：是兩個(gè)或者兩個(gè)以上的線(xiàn)程被無(wú)限的阻塞，線(xiàn)程之間互相等待所需資源。

線(xiàn)程死鎖產(chǎn)生的條件：

• 當(dāng)兩個(gè)線(xiàn)程相互調(diào)用Join（）方法。
• 當(dāng)兩個(gè)線(xiàn)程使用嵌套的同步代碼塊的時(shí)候，一個(gè)線(xiàn)程占用了另一個(gè)線(xiàn)程的鎖，互相等待阻塞，就有可能產(chǎn)生死鎖。

下面看代碼：

代碼1：死鎖的案例

package com.lp.ecjtu.Thread;/* 死鎖：常見(jiàn)情景之一：同步的嵌套。*/ class Ticket implements Runnable {private int num = 100;Object obj = new Object();boolean flag = true;public void run(){if(flag)while(true){synchronized(obj)//同步代碼塊里面調(diào)用同步函數(shù) {show();}}elsewhile(true)this.show();}public synchronized void show()//同步函數(shù)里面的調(diào)用同步代碼塊 {synchronized(obj){if(num>0){try{Thread.sleep(10);}catch (InterruptedException e){}System.out.println(Thread.currentThread().getName()+".....sale...."+num--);}}} }public class DeathLockThread1 {public static void main(String[] args) {Ticket t = new Ticket();Thread t1 = new Thread(t);Thread t2 = new Thread(t);t1.start();try{Thread.sleep(10);}catch(InterruptedException e){}t.flag = false;t2.start();} }

代碼2：

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package com.lp.ecjtu.Thread;class DeathLockRunable implements Runnable{private boolean flag;public DeathLockRunable(boolean flag){this.flag = flag;}@Overridepublic void run() {if(flag){synchronized (Lock.mylock1){System.out.println("if mylock1"+Thread.currentThread().getName());synchronized (Lock.mylock2){System.out.println("if mylock2"+Thread.currentThread().getName());}}}else{synchronized (Lock.mylock2){System.out.println("else mylock2"+Thread.currentThread().getName());synchronized (Lock.mylock1){System.out.println("else mylock1"+Thread.currentThread().getName());}}}}}class Lock{static Object mylock1 = new Object();static Object mylock2 = new Object();}public class DeathLockThread{public static void main(String[] args){Thread t1 = new Thread(new DeathLockRunable(true));Thread t2 = new Thread(new DeathLockRunable(false));t1.start();t2.start();}}

輸出結(jié)果：if mylock1Thread-0
else mylock2Thread-1

?

總結(jié)

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