LeetCode（多线程）- 1115. 交替打印 FooBar

题目链接：点击打开链接

题目大意：略。

解题思路：略。

相关企业

• 阿里巴巴
• 亚马逊（Amazon）

AC 代码

// 手太阴肺经 BLOCKING Queue
public class FooBar {
    private int n;
    private BlockingQueue<Integer> bar = new LinkedBlockingQueue<>(1);
    private BlockingQueue<Integer> foo = new LinkedBlockingQueue<>(1);
    public FooBar(int n) {
        this.n = n;
    }
    public void foo(Runnable printFoo) throws InterruptedException {
        for (int i = 0; i < n; i++) {
            foo.put(i);
            printFoo.run();
            bar.put(i);
        }
    }

    public void bar(Runnable printBar) throws InterruptedException {
        for (int i = 0; i < n; i++) {
            bar.take();
            printBar.run();
            foo.take();
        }
    }
}

// 手阳明大肠经CyclicBarrier 控制先后
class FooBar6 {
    private int n;

    public FooBar6(int n) {
        this.n = n;
    }

    CyclicBarrier cb = new CyclicBarrier(2);
    volatile boolean fin = true;

    public void foo(Runnable printFoo) throws InterruptedException {
        for (int i = 0; i < n; i++) {
            while(!fin);
            printFoo.run();
            fin = false;
            try {
                cb.await();
            } catch (BrokenBarrierException e) {}
        }
    }

    public void bar(Runnable printBar) throws InterruptedException {
        for (int i = 0; i < n; i++) {
            try {
                cb.await();
            } catch (BrokenBarrierException e) {}
            printBar.run();
            fin = true;
        }
    }
}

// 手少阴心经 自旋 + 让出CPU
class FooBar5 {
    private int n;

    public FooBar5(int n) {
        this.n = n;
    }

    volatile boolean permitFoo = true;

    public void foo(Runnable printFoo) throws InterruptedException {     
        for (int i = 0; i < n; ) {
            if(permitFoo) {
        	    printFoo.run();
            	i++;
            	permitFoo = false;
            }else{
                Thread.yield();
            }
        }
    }

    public void bar(Runnable printBar) throws InterruptedException {       
        for (int i = 0; i < n; ) {
            if(!permitFoo) {
        	printBar.run();
        	i++;
        	permitFoo = true;
            }else{
                Thread.yield();
            }
        }
    }
}

// 手少阳三焦经 可重入锁 + Condition
class FooBar4 {
    private int n;

    public FooBar4(int n) {
        this.n = n;
    }
    Lock lock = new ReentrantLock(true);
    private final Condition foo = lock.newCondition();
    volatile boolean flag = true;
    public void foo(Runnable printFoo) throws InterruptedException {
        for (int i = 0; i < n; i++) {
            lock.lock();
            try {
            	while(!flag) {
                    foo.await();
                }
                printFoo.run();
                flag = false;
                foo.signal();
            }finally {
            	lock.unlock();
            }
        }
    }

    public void bar(Runnable printBar) throws InterruptedException {
        for (int i = 0; i < n;i++) {
            lock.lock();
            try {
            	while(flag) {
                    foo.await();
            	}
                printBar.run();
                flag = true;
                foo.signal();
            }finally {
            	lock.unlock();
            }
        }
    }
}

// 手厥阴心包经 synchronized + 标志位 + 唤醒
class FooBar3 {
    private int n;
    // 标志位，控制执行顺序，true执行printFoo，false执行printBar
    private volatile boolean type = true;
    private final Object foo=  new Object(); // 锁标志

    public FooBar3(int n) {
        this.n = n;
    }
    public void foo(Runnable printFoo) throws InterruptedException {
        for (int i = 0; i < n; i++) {
            synchronized (foo) {
                while(!type){
                    foo.wait();
                }
                printFoo.run();
                type = false;
                foo.notifyAll();
            }
        }
    }

    public void bar(Runnable printBar) throws InterruptedException {
        for (int i = 0; i < n; i++) {
            synchronized (foo) {
                while(type){
                    foo.wait();
                }
                printBar.run();
                type = true;
                foo.notifyAll();
            }
        }
    }
}

// 手太阳小肠经 信号量 适合控制顺序
class FooBar2 {
    private int n;
    private Semaphore foo = new Semaphore(1);
    private Semaphore bar = new Semaphore(0);
    public FooBar2(int n) {
        this.n = n;
    }

    public void foo(Runnable printFoo) throws InterruptedException {
        for (int i = 0; i < n; i++) {
            foo.acquire();
        	printFoo.run();
            bar.release();
        }
    }
    public void bar(Runnable printBar) throws InterruptedException {
        for (int i = 0; i < n; i++) {
            bar.acquire();
        	printBar.run();
            foo.release();
        }
    }
}

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