代码如下：

package com.java.day19ThreadLock;
// 2个线程交替打印数字，线程之间的通信，等待和唤醒
public class ThreadPrint {
    static int num = 0;

    public static void main(String[] args) {

        // 锁对象
        Object obj = new Object();
        new Thread(){
            @Override
            public void run() {
                System.out.println("准备开始打印了...");
                while (true){
                    synchronized (obj){
                        try {
                            // 线程等待
                            obj.wait();
                            System.out.println(num);
                            num++;
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }

            }
        }.start();


        new Thread(){
            @Override
            public void run() {
                while (true){
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    synchronized (obj){
                        System.out.println(num);
                        num++;
                        // 唤醒线程
                        obj.notify();
                    }
                }

            }
        }.start();
    }
}

运行如图：