juc相关知识

1、wait会释放锁，而sleep不会释放锁。

代码证明：

package com.xiangwen.day2;

public class DeadLockTest {
    public static void main(String[] args) {
        String a="aa";
        String b="bb";
        new Thread(new MyThread(a,b),"t1").start();
        new Thread(new MyThread(b,a),"t2").start();
    }
}
class MyThread implements Runnable{
    private Object a;
    private Object b;
    public MyThread(Object a,Object b){
        this.a=a;
        this.b=b;
    }
    @Override
    public void run() {
        synchronized (a){
            System.out.println("当前线程外"+Thread.currentThread().getName());
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
                if ("aa".equals(a)) {//t1是获取了aa的锁，t2是获取了bb的锁，现在t1wait，释放了aa的锁。t2可以跑完。
                    try {
                        a.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        synchronized (b){
            System.out.println("当前线程里"+Thread.currentThread().getName());
        }
        }
    }

　　运行截图