java死鎖分析

Java 的死鎖分析

(*)JDK: 提供強大診斷工具：Thread Dump ----> 文本信息

(*)windows: ctrl+break /(fn+B) 打印鎖信息

linux: kill -3 pid ----> 命令：jps 打印鎖信息

Java stack information for the threads listed above:

===================================================

"Thread-1":

at ThreadB.run(DeadLock.java:68)

-waiting to lock <0x244f6498> (a java.lang.Object)

-locked <0x244f64a0> (a java.lang.Object) "Thread-0":
at ThreadA.run(DeadLock.java:41)

-waiting to lock <0x244f64a0> (a java.lang.Object)

-locked <0x244f6498> (a java.lang.Object)

Found 1 deadlock.

代碼如下
public class DeadLock {

final Object lockA = new Object();
final Object lockB = new Object();

public static void main(String[] args) {
    DeadLock demo = new DeadLock();
    demo.startLock();
}

public void startLock(){
    ThreadA a= new ThreadA(lockA,lockB);
    ThreadB b= new ThreadB(lockA,lockB);

    //start threads
    a.start();
    b.start();
}

}

class ThreadA extends Thread{

private Object lockA = null;
private Object lockB = null;

public ThreadA(Object a, Object b){
    this.lockA = a;
    this.lockB = b;
}

public void run() {
    synchronized (lockA) {
        System.out.println("*** Thread A: ***: Lock A" );
        try {
            sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        synchronized (lockB) {
            System.out.println("*** Thread A: ***: Lock B" );
        }
    }

    System.out.println("*** Thread A: ***: Finished" );
}

}

class ThreadB extends Thread{

private Object lockA = null;
private Object lockB = null;

public ThreadB(Object a, Object b){
    this.lockA = a;
    this.lockB = b;
}
public void run() {
    synchronized (lockB) {
        System.out.println("*** Thread B: ***: Lock B" );
        try {
            sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        synchronized (lockA) {
            System.out.println("*** Thread B: ***: Lock A" );
        }
    }   

    System.out.println("*** Thread B: ***: Finished" );
}

}