注意點

多執行緒操作資源類，牢記三步走：

• 判斷
• 幹活
• 喚醒

synchronized版

//A : num + 1
//B : num - 1
public class A {

    public static void main(String[] args) {

        Data data = new Data();

        new Thread(() -> {
            for (int i = 0;i<10;i++){
                try {
                    data.increment();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"A").start();

        new Thread(() -> {
            for (int i = 0;i<10;i++){
                try {
                    data.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"B").start();

        new Thread(() -> {
            for (int i = 0;i<10;i++){
                try {
                    data.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"C").start();

        new Thread(() -> {
            for (int i = 0;i<10;i++){
                try {
                    data.increment();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"D").start();
    }
}

//等待，業務，通知
class Data{

    private int number = 0;

    //+1
    public synchronized void increment() throws InterruptedException {
        //while的作用就是防止虛假喚醒
        while(number != 0){
            this.wait();
        }
        number++;
        System.out.println(Thread.currentThread().getName()+"< "+number);
        //通知其他執行緒，我+1完畢了
        this.notifyAll();
    }

    //-1
    public synchronized void decrement() throws InterruptedException {
        while(number == 0){
           this.wait();
        }
        number--;
        System.out.println(Thread.currentThread().getName()+"< "+number);
        //通知其他執行緒，我-1完畢了
        this.notifyAll();
    }
}

阻塞佇列版

/使用阻塞佇列實現生產者，消費者模型
//volatile/CAS/AutomicReference/BlockingQueue/執行緒互動
public class BlockingQueueCustomerProductor {

    public static void main(String[] args) throws InterruptedException {

        MySource mySource = new MySource(new ArrayBlockingQueue(10));

        new Thread(() -> {
            try {
                mySource.myProd();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"AAA").start();

        new Thread(() -> {
            try {
                mySource.myConsumer();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        },"BBB").start();

        TimeUnit.SECONDS.sleep(5);

        System.out.println("5秒已經過了，開始結束吧");
        mySource.stop();
    }

}

//判斷，幹活，通知
class MySource{

    private volatile boolean flag = true;  //預設開啓，進行生產
    private volatile boolean flag2 = true; //預設開啓，進行消費

    private AtomicInteger atomicInteger = new AtomicInteger();

    BlockingQueue<String> blockingQueue = null;

    public MySource(BlockingQueue blockingQueue){
        this.blockingQueue = blockingQueue;
        System.out.println(blockingQueue.getClass().getName());
    }

    public void myProd() throws InterruptedException {
        String data = null;
        boolean retValue;
        while (flag){
            data = atomicInteger.incrementAndGet()+"";
            retValue = blockingQueue.offer(data,2, TimeUnit.SECONDS);
            if (retValue){
                System.out.println(Thread.currentThread().getName()+"插入成功: "+data);
            }else {
                System.out.println(Thread.currentThread().getName()+"插入失敗: "+data);
            }
            TimeUnit.SECONDS.sleep(1);
        }
        System.out.println(Thread.currentThread().getName()+ "\t大老闆叫停生產: flag=false");
    }

    public void myConsumer() throws InterruptedException {
        String result = null;
        while (flag2){
            result = blockingQueue.poll(2,TimeUnit.SECONDS);
            if (null == result || result.equalsIgnoreCase(""))
            {
                flag2 = false;
                System.out.println(Thread.currentThread().getName()+"\t 超過兩秒鐘沒有渠道，消費退出");
            }else {
                System.out.println(Thread.currentThread().getName() + "消費佇列: " + result + " 成功");
            }
        }
    }

    public void stop(){
        this.flag = false;
    }
}