Foo.java

package thread.leetcode1114;

/**
 * 按序打印
 * LeetCode 1114 https://leetcode-cn.com/problems/print-in-order/
 *
 * @author yangyi 2021年05月02日15:18:19
 */
public class Foo {

    private boolean firstFinish = false;
    private boolean secondFinish = false;
    private final Object lock = new Object();

    public Foo() {

    }

    public void first(Runnable printFirst) throws InterruptedException {
        synchronized (lock) {
            // printFirst.run() outputs "first". Do not change or remove this line.
            printFirst.run();
            firstFinish = true;
            lock.notifyAll();
        }

    }

    public void second(Runnable printSecond) throws InterruptedException {
        synchronized (lock) {
            while (!firstFinish) {
                lock.wait();
            }
            // printSecond.run() outputs "second". Do not change or remove this line.
            printSecond.run();
            secondFinish = true;
            lock.notifyAll();
        }
    }

    public void third(Runnable printThird) throws InterruptedException {
        synchronized (lock) {
            while (!secondFinish) {
                lock.wait();
            }
            // printThird.run() outputs "third". Do not change or remove this line.
            printThird.run();
            lock.notifyAll();
        }

    }

    public static void main(String[] args) throws InterruptedException {
        Foo foo = new Foo();
        Runnable printFirst = () -> System.out.println("first");
        Runnable printSecond = () -> System.out.println("second");
        Runnable printThird = () -> System.out.println("third");
        new Thread(() -> {
            try {
                foo.third(printThird);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }).start();
        new Thread(() -> {
            try {
                foo.first(printFirst);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }).start();
        new Thread(() -> {
            try {
                foo.second(printSecond);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }).start();
    }
}