LeetCode刷题之旅【多线程篇】简单 - 1：按序打印

LeetCode刷题之旅【多线程篇】简单 - 1：按序打印

2019年11月15日

题目

注意:

尽管输入中的数字似乎暗示了顺序，但是我们并不保证线程在操作系统中的调度顺序。

你看到的输入格式主要是为了确保测试的全面性。

解题1：CountDownLatch

class Foo { private CountDownLatch countDownLatchTwo = new CountDownLatch(1); private CountDownLatch countDownLatchThree = new CountDownLatch(1); public Foo() { } public void first(Runnable printFirst) throws InterruptedException { // printFirst.run() outputs "first". Do not change or remove this line. printFirst.run(); countDownLatchTwo.countDown(); } public void second(Runnable printSecond) throws InterruptedException { countDownLatchTwo.await(); // printSecond.run() outputs "second". Do not change or remove this line. printSecond.run(); countDownLatchThree.countDown(); } public void third(Runnable printThird) throws InterruptedException { countDownLatchThree.await(); // printThird.run() outputs "third". Do not change or remove this line. printThird.run(); }}

解题2

class Foo { private boolean firstFinished; private boolean secondFinished; private 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(); firstFinished = true; lock.notifyAll(); } } public void second(Runnable printSecond) throws InterruptedException { synchronized (lock) { while (!firstFinished) { lock.wait(); } // printSecond.run() outputs "second". Do not change or remove this line. printSecond.run(); secondFinished = true; lock.notifyAll(); } } public void third(Runnable printThird) throws InterruptedException { synchronized (lock) { while (!secondFinished) { lock.wait(); } // printThird.run() outputs "third". Do not change or remove this line. printThird.run(); } }}

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