1. 一個生產者和一個消費者：操作值

1.1 公共值

public class ValueObject {
    public static String value = "";
}

1.2 生產者

public class Producer {
    private String lock;

    public Producer(String lock){
        super();
        this.lock = lock;
    }

    public void setValue(){
        try{
            synchronized
 
 (lock){
                //如果公共值還沒有被消費，則當前執行緒等待
                if (!ValueObject.value.equalsIgnoreCase("")){
                    lock.wait();
                }else {
                    String value = System.currentTimeMillis() + "_" + System.nanoTime();
                    System.out.println("set value is "
 
 + value);
                    //生產者給公共值賦值
                    ValueObject.value = value;
                }
                //通知消費者可以消費了
                lock.notify();
            }
        }catch (InterruptedException e){
            e.printStackTrace();
        }
    }
}

注意： 執行到lock.wait()這句，wait()立即釋放鎖。

1.3 消費者

public class Consumer {
    private String lock;

    public Consumer(String lock){
        super();
        this.lock = lock;
    }

    public void getValue(){
        try{
            synchronized (lock){
                if (ValueObject.value.equals("")){
                    lock.wait();
                }
                System.out.println("get value is " + ValueObject.value);
                ValueObject.value = "";
                lock.notify();
            }
        }catch (InterruptedException e){
            e.printStackTrace();
        }
    }
}

1.4 生產者執行緒

public class ThreadP extends Thread {
    private Producer producer;

    public ThreadP(Producer producer){
        super();
        this.producer = producer;
    }

    @Override
    public void run(){
        while (true){
            producer.setValue();
        }
    }
}

1.5 消費者執行緒

public class ThreadC extends Thread {
    private Consumer consumer;

    public ThreadC(Consumer consumer){
        super();
        this.consumer = consumer;
    }

    @Override
    public void run(){
        while (true){
            consumer.getValue();
        }
    }
}

1.6 Test

public class Test {
    public static void main(String[] args) {
        String lock = new String("");

        Producer producer = new Producer(lock);
        ThreadP threadP = new ThreadP(producer);

        Consumer consumer = new Consumer(lock);
        ThreadC threadC = new ThreadC(consumer);

        threadP.start();
        threadC.start();
    }
}

1.7 執行結果

...
set value is 1541748157877_7058115684144
get value is 1541748157877_7058115684144
set value is 1541748157877_7058115845581
get value is 1541748157877_7058115845581
set value is 1541748157877_7058115937711
get value is 1541748157877_7058115937711
set value is 1541748157877_7058116052944
get value is 1541748157877_7058116052944
...

set和get是交替出現的