线程死锁
死锁是指两个或两个以上的线程在执行过程中,由于竞争资源或者由于彼此通信而造成的一种阻塞的现象,若无外力作用,它们都将无法推进下去(百度百科)。
代码示例:
/**
* @ClassName ThreadDeadLock
* @projectName: object1
* @author: Zhangmingda
* @description: XXX
* date: 2021/4/22.
*/
public class ThreadDeadLock {
private static class MyDeadLockRunnable implements Runnable{
private Object lockA = new Object();
private Object lockB = new Object(); @Override
public void run() {
String tName = Thread.currentThread().getName();
try {
if ("A".equals(tName)){
runA();
}else {
runB();
}
}catch (InterruptedException e){e.printStackTrace();}
} private void runA() throws InterruptedException {
synchronized (lockA){
System.out.println("我开始运行了,我是A");
Thread.sleep(1000);
synchronized (lockB){
System.out.println("我运行完了,我是A");
}
}
} private void runB() throws InterruptedException {
synchronized (lockB){
System.out.println("我开始运行了,我是B");
Thread.sleep(1000);
synchronized (lockA){
System.out.println("我运行完了,我是B");
}
}
}
} public static void main(String[] args) {
Runnable myDeadlock = new MyDeadLockRunnable();
new Thread(myDeadlock,"A").start();
new Thread(myDeadlock,"B").start();
}
}
运行结果:
打印了两句话:
如何判断我们写的程序是有死锁
1,jps -l 命令来获取对应的进程pid:
2,获取到对应的Pid之后用jstack命令来查看是否有死锁:
jstack -l 26640