public class ThreadTest {

    //声明一个线程可视化的list集合
    public static List<String> list = new ArrayList<>();

    public static void main(String[] args) {
        Object lock = new Object();

        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (lock) {
                    for (int i = 0; i < 10; i++) {
                        list.add("lenny");
                        System.out.println(Thread.currentThread().getName() + "往list增加了新项目");
                        if (list.size() == 5) {
                            lock.notify(); //通知lock挂起的线程 继续执行 synchronized 块代码 执行完成后 释放锁
                            System.out.println("当前线程：" + Thread.currentThread().getName() + "，已经发出通知");
                        }
                    }
                }
            }
        }, "t1");

        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                synchronized (lock) {
                    if (list.size() != 5) {
                        try {
                            lock.wait(); //此处线程挂起 释放lock
                            System.out.println("list长度"+list.size());
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                    System.out.println("当前线程：" + Thread.currentThread().getName() + "，收到通知");
                }
            }
        }, "t2");

        t2.start();
        t1.start();
    }
}