leetcode中等1115交替打印 FooBar

Posted 2022-02-19 qq_40707462

1115、交替打印 FooBar

交替打印 n 次，一个线程打印 foo ，另一个打印 bar

public class test 

    public static void main(String[] args) 
        //a，b这两个runnable 
        Runnable a = ()->
            System.out.print("foo");
        ;

        Runnable b = ()->
            System.out.print("bar");
        ;

        FooBar fooBar = new FooBar(11);

        //真正start的是这个。lamada表达式创建的匿名类
        new Thread(()->
            try 
                fooBar.bar(b);
             catch (InterruptedException e) 
                e.printStackTrace();
            
        ).start();

        new Thread(()->
            try 
                fooBar.foo(a);
             catch (InterruptedException e) 
                e.printStackTrace();
            
        ).start();
    


class FooBar 
    private int n;
    private Object obj = new Object();
    private volatile boolean fooExec = true;

    public FooBar(int n) 
        this.n = n;
    

    public void foo(Runnable printFoo) throws InterruptedException 

        for (int i = 0; i < n; i++) 
            synchronized (obj) 
                if (!fooExec) //fooExec为false时，该线程等待，为true的时候执行下面的操作
                    obj.wait();
                
                printFoo.run();
                fooExec = false;
                obj.notifyAll();//唤醒其他线程
            

        
    

    public void bar(Runnable printBar) throws InterruptedException 

        for (int i = 0; i < n; i++) 
            synchronized (obj) 
                if (fooExec) 
                    obj.wait();
                
                printBar.run();
                fooExec = true;
                obj.notifyAll();
            

        
    

补充：两个线程循环交替打印1-100。

public class DoubleThreadPrintNumber 
    public static int i = 1;
    public static Object lock = new Object();
    private static AtomicInteger num = new AtomicInteger(1);
    private static CountDownLatch countDownLatch = new CountDownLatch(2);
    public static void main(String[] args) throws InterruptedException 
        System.out.println("请输入要执行的操作：");
        System.out.println("1、使用CountDownLatch实现");
        System.out.println("2、使用syncchronized实现");
        System.out.println("3、使用AtomicInteger实现");
        //创建Scanner对象，接受从控制台输入
        Scanner input=new Scanner(System.in);
        //接受String类型
        String str=input.next();
        switch (str)
            case "1": doCountDownLatch();
                break;
            case "2":doSynchronized() ;break;
            case "3":doAtomicInteger();
                break;
                default:doAtomicInteger();
        
    
    /**
     * countdownlatch 实现
     */
    private static void  doCountDownLatch()
        Thread t1 = new Thread() 
            @Override public void run() 
                while (num.intValue() < 100) 
                    if (num.intValue() % 2 == 1) 

                        System.out.println("奇数线程:" + num.intValue());
                        num.incrementAndGet();
                    
                    countDownLatch.countDown();
                
            
        ;

        Thread t2 = new Thread() 
            @Override public void run() 
                while (num.intValue() <= 100) 
                    if (num.intValue() % 2 == 0) 
                        System.out.println("偶数线程:" + num.intValue());
                        num.incrementAndGet();
                    
                    countDownLatch.countDown();
                
            
        ;
        t1.start();
        t2.start();
        try 
            countDownLatch.await();

        catch (Throwable e)
            System.out.println(e);
        
    
    /**
     * synchronized 关键字实现
     */
    private static void doSynchronized()
        int TOTAL = 100;
        Thread thread1 = new Thread(() -> 
            while (i <= TOTAL) 
                synchronized (lock) 
                    if (i % 2 == 1) 
                        System.out.println("i=" + i++);
                        lock.notify();
                        System.out.println("奇数打印完毕，释放锁");
                     else 
                        try 
                            System.out.println("奇数锁等待");

                            lock.wait();
                         catch (InterruptedException e) 
                            e.printStackTrace();
                        
                    
                
            
        );
        Thread thread2 = new Thread(() -> 
            while (i <= TOTAL) 
                synchronized (lock) 
                    if (i % 2 == 0) 
                        System.out.println("i=" + i++);
                        lock.notify();
                        System.out.println("偶数打印完毕，释放锁");

                     else 
                        try 
                            System.out.println("偶数锁等待");
                            lock.wait();
                         catch (InterruptedException e) 
                            e.printStackTrace();
                        
                    
                
            
        );
        thread1.start();
        thread2.start();
    
    /**
     * AtomicInteger实现
     */
    public static void doAtomicInteger() 
        ReentrantLock reentrantLock = new ReentrantLock();
        Condition condition = reentrantLock.newCondition();
        new Thread(new Runnable() 
        int i =1;
        // 第一个线程
            @Override public void run() 
                for ( ;num.intValue()<=100;)
                    if (num.intValue()%3==0)
                       // reentrantLock.lock();
                        System.out.println(num.intValue());
                        num.addAndGet(1);
                        //reentrantLock.unlock();
                    else 

                    
                
            
        ).start();
        // 第二个线程
        new Thread(new Runnable() 
            @Override public void run() 
                for (;num.intValue()<=100;)
                    if (num.intValue()%3==1)
                        System.out.println(num.intValue());
                        num.addAndGet(1);
                    //    reentrantLock.unlock();

                    else 
                     //  reentrantLock.lock();

                    
                
            
        ).start();
        // 第二个线程
        new Thread(new Runnable() 
            @Override public void run() 
                for (;num.intValue()<=100;)
                    if (num.intValue()%3==2)
                        System.out.println(num.intValue());
                        num.addAndGet(1);
                        //    reentrantLock.unlock();

                    else 
                        //  reentrantLock.lock();

                    
                
            
        ).start();