Leetcode Concurrency本地调试 - Q1114

并发项目的经历不多，之前没见过参数是Runnable的方法，所以虽然题目本身不难，但还是花了一番力气去理解到底怎么运行调试这段代码，记录一下。

class Foo {     
        
    Semaphore twolock = new Semaphore(1);;
    Semaphore threelock = new Semaphore(1);
        
    public Foo() {
        try {           
            twolock.acquire();
            threelock.acquire();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }   
    }
        
    public void first(Runnable printFirst) throws InterruptedException {
        printFirst.run();
        twolock.release();
    }
        
    public void second(Runnable printSecond) throws InterruptedException {
        twolock.acquire();
        printSecond.run();
        threelock.release();
    }

    public void third(Runnable printThird) throws InterruptedException {
        threelock.acquire();
        printThird.run();
    }

        public static void main(String[] args) {
                Foo foo = new Foo();
        
        //create a runnable, and then create a thread base on it
                //wrap the runnables in foo functions, so they can share the same foo object
                Runnable r1 = new Runnable() {
            @Override
            public void run() {
                System.out.println("one");
            }
        };
        Thread t1 = new Thread(() -> {
                        try {
                                foo.first(r1);
                        } catch (InterruptedException e) {
                                 e.printStackTrace();
                        }
                });

                //if runnable is simple, can directly override it in the thread initialization
                Thread t2 = new Thread(() -> {
                         try {
                                 foo.second(() -> System.out.print("two"));
                         } catch (InterruptedException e) {
                                 e.printStackTrace();
                         }
                 });

                Thread t3 = new Thread(() -> {
                         try {
                                 foo.third(() -> System.out.print("three"));
                         } catch (InterruptedException e) {
                                 e.printStackTrace();
                         }
                 });
        
                //run threads
                try {
                t1.start();
                t2.start();
                t3.start();
        
                t1.join();
                t2.join();
                t3.join();
         } catch (InterruptedException e) {
                e.printStackTrace();
         }
        }
}

Leetcode CN - 1114 Print in Order 我的题解