【JAVA】線程 打印ABC

通過控制變量的方式

public class Test {

    public static  int num = 1;

    public static void main(String[] args) {

        Thread a = new Thread(new Runnable() {
            @Override
            public void run(){
                while (true){
                    if(num == 30){
                        break;
                    }
                    if(num % 3 == 1){
                        System.out.println("A");
                        num++;
                    }
                }
            }
        });
        Thread b = new Thread(new Runnable() {
            @Override
            public void run(){
                while (true){
                    if(num == 30){
                        break;
                    }
                    if(num % 3 == 2){
                        System.out.println("B");
                        num++;
                    }
                }
            }
        });
        Thread c = new Thread(new Runnable() {
            @Override
            public void run(){
                while (true){
                    if(num == 30){
                        break;
                    }
                    if(num % 3 == 0){
                        System.out.println("C");
                        num++;
                    }
                }
            }
        });
        a.start();
        b.start();
        c.start();
    }

}

通過用synchronized、wait、notifyAll實現

public class Test {

    public  static  int num = 1;

    public static class Pabc implements Runnable{
        private int id;
        private char[] ch = { 'C', 'A', 'B' };

        public Pabc(int id){
            this.id = id;
        }

        @Override
        public void run(){
            while (num <= 30){
                synchronized (Pabc.class){
                    if (num  % 3 == id){
                        System.out.println(ch[id]);
                        num++;
                        Pabc.class.notifyAll();
                    }else{

                        try {
                            Pabc.class.wait();
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        }
    }

    public static void main(String[] args) {
        new Thread(new Pabc(1)).start();
        new Thread(new Pabc(2)).start();
        new Thread(new Pabc(0)).start();
    }

}

Condition 和 Lock 一起使用

    public  static  int num = 1;
    final  static  ReentrantLock lock = new ReentrantLock();
    final static Condition condition = lock.newCondition();

    public static class Pabc implements Runnable{
        private int id;
        private char[] ch = { 'C', 'A', 'B' };

        public Pabc(int id){
            this.id = id;
        }

        @Override
        public void run(){
            lock.lock();
            try {
                while (num <= 30){
                    if(num % 3 != id){
                        condition.await();
                    }else{
                        System.out.println(ch[id]);
                        num++;
                        condition.signalAll();
                    }
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }finally {
                lock.unlock();
            }

        }
    }

    public static void main(String[] args) {
        new Thread(new Pabc(1)).start();
        new Thread(new Pabc(2)).start();
        new Thread(new Pabc(0)).start();
    }