import java.util.concurrent.locks.Condition;

import java.util.concurrent.locks.ReentrantLock;

/**

* https://leetcode-cn.com/problems/print-foobar-alternately/

*/

public class PrintFooBar {

public static void main(String[] args) {

FooBar fooBar = new FooBar(4);

new Thread(() -> {

try {

fooBar.foo(new PrintFoo());

} catch (InterruptedException e) {

e.printStackTrace();

}

},"FOO").start();

new Thread(() -> {

try {

fooBar.bar(new PrintBar());

} catch (InterruptedException e) {

e.printStackTrace();

}

},"Bar").start();

}

}

class FooBar {

private int n;

// 方式一：lock condition

private ReentrantLock lock;

private Condition conditionFoo;

private Condition conditionBar;

private volatile boolean flag;

// 方式二：semaphore

// private Semaphore semaphoreFoo = new Semaphore(1);

// private Semaphore semaphoreBar = new Semaphore(0);

public FooBar(int n) {

this.n = n;

this.lock = new ReentrantLock();

this.conditionFoo = this.lock.newCondition();

this.conditionBar = this.lock.newCondition();

this.flag = false;

}

public void foo(Runnable printFoo) throws InterruptedException {

for (int i = 0; i < n; i++) {

lock.lock();

while (flag)

conditionFoo.await();

// printFoo.run() outputs "foo". Do not change or remove this line.

printFoo.run();

flag = true;

conditionBar.signal();

lock.unlock();

}

}

public void bar(Runnable printBar) throws InterruptedException {

for (int i = 0; i < n; i++) {

lock.lock();

while (!flag)

conditionBar.await();

// printBar.run() outputs "bar". Do not change or remove this line.

printBar.run();

flag = false;

conditionFoo.signal();

lock.unlock();

}

}

}

class PrintFoo implements Runnable {

@Override

public void run() {

System.out.print("Foo");

}

}

class PrintBar implements Runnable {

@Override

public void run() {

System.out.println("Bar");

}

}