??Object類的方法：等待wait() ， 喚醒隊首線程notify() ， 喚醒全部等待線程notifyAll()。利用等待和喚醒實現(xiàn)Producer線程、Consumer線程的互斥訪問Message對象。
代碼如下：

package ThreadDemo;

class Message {
    private String msg = "";
    private boolean flag = true; //記錄型信號量，規(guī)定true表示沒有消息（允許生產(chǎn)、不許消費），false表示已有消息（不許生產(chǎn)、允許消費）
    
    public synchronized void setMessage(String msg) {
        if(flag==false) {   
            try {
                super.wait();   //不許生產(chǎn)、讓Producer線程等待
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        this.msg=msg;
        flag = false;   //生產(chǎn)完成，改變信號量、喚醒Consumer
        super.notify();
    }
    
    public synchronized String getMessage() {
        if(flag==true) {    
            try {
                super.wait();   //不許消費、讓Consumer線程等待
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        try {
        return "msg = "+this.msg;
        }
        finally {       //return后用finally確保指令執(zhí)行
        flag = true;    //消費完成，改變信號量、喚醒Producer
        super.notify();
        }
    }
}

class Producer implements Runnable{
    private Message msg;
    
    public Producer(Message msg) {
        this.msg = msg;
    }
    @Override
    public void run() {
        for(int x=0;x<30;x++) {
            if(x%2==0) {
                msg.setMessage("夏天，穿短袖短褲");
            }
            else {
                msg.setMessage("冬天，換秋衣秋褲");
            }
        }
    }
}

class Consumer implements Runnable{
    private Message msg;
    
    public Consumer(Message msg) {
        this.msg = msg;
    }
    @Override
    public void run() {
        for(int x=0;x<30;x++) {
            System.out.println(msg.getMessage());
        }
    }
}

public class Main {
    public static void main(String[] args){
        Message msg = new Message();
        new Thread(new Producer(msg)).start();  //啟動生產(chǎn)者線程
        new Thread(new Consumer(msg)).start();  //啟動消費者線程
    }
}