JUC个人学习笔记19---各种锁的理解

根据b站UP主狂神说JUC课程所写的个人学习笔记

视频地址：https://www.bilibili.com/video/BV1B7411L7tE?from=search&seid=14761503393031794075

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1.公平锁/非公平锁

公平锁:非常公平，不能插队，先来后到

非公平锁:可以插队(默认)

public ReentrantLock() {
    sync = new NonfairSync();
}

public ReentrantLock(boolean fair) {
    sync = fair ? new FairSync() : new NonfairSync();
}

2.可重入锁

可重入锁(递归锁)

3.自旋锁

4.死锁

public class DeadLockDemo {
    public static void main(String[] args) {
        String lockA = "lockA";
        String lockB = "lockB";
        new Thread(new MyThread(lockA,lockB),"T1").start();
        new Thread(new MyThread(lockB,lockA),"T2").start();

    }

}
class MyThread implements Runnable{
    private String lockA;
    private String lockB;

    public MyThread(String lockA ,String lockB){
        this.lockA = lockA;
        this.lockB = lockB;
    }

    @Override
    public void run() {
        synchronized (lockA){
            System.out.println(Thread.currentThread().getName()+"lock:"+lockA+" get"+lockB);
            try {
                TimeUnit.SECONDS.sleep(2);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

        synchronized (lockB){
            System.out.println(Thread.currentThread().getName()+"lock:"+lockB+" get"+lockA);


        }

    }
}}
解决问题:

1.使用jps定位进程号

2.查看进程信息 jstack 进程号