在家換衣服時，突然門鈴響了，原來郵遞員送快遞了。因為衣服不能換了一半就出去，所以對郵遞員將，請您稍等。在把門開啟，說“讓您久等了”，Guarded Suspension Pattern 就是適合這種情況的

下面我們用個簡單的例子來進行說明（範例由5個檔案組成）： 大家在要注意為什麼要加synchronized ，它想保護的究竟是什麼，為什麼要wait，為什麼put後要nitifyAll();

Main.java--呼叫類

public class Main {
    public static void main(String[] args) {
        RequestQueue requestQueue = new RequestQueue();
        new ClientThread(requestQueue, "郵遞員", 3141592L).start();
        new ServerThread(requestQueue, "主人", 6535897L).start();
    }
}

Request.java--請求類

public class Request {
    private final String name;
    public Request(String name) {
        this.name = name;
    }
    public String getName() {
        return name;
    }
    public String toString() {
        return "[ Request " + name + " ]";
    }
}

RequestQueue.java--請求佇列

import java.util.LinkedList;

public class RequestQueue {
    private final LinkedList queue = new LinkedList();
   
    public synchronized Request getRequest() {
        while (queue.size() <= 0) {
            try {                                  
                wait();
            } catch (InterruptedException e) {     
            }                                      
        }                                          
        return (Request)queue.removeFirst();
    }
   
    public synchronized void putRequest(Request request) {
        queue.addLast(request);
        notifyAll();
    }
}

ClientThread.java--送出請求類

import java.util.Random;

public class ClientThread extends Thread {
    private Random random;
    private RequestQueue requestQueue;
    public ClientThread(RequestQueue requestQueue, String name, long seed) {
        super(name);
        this.requestQueue = requestQueue;
        this.random = new Random(seed);
    }
    public void run() {
        for (int i = 0; i < 10000; i++) {
            Request request = new Request("No." + i);
            System.out.println(Thread.currentThread().getName() + " 送出請求 " + request);
            requestQueue.putRequest(request);
            try {
                Thread.sleep(random.nextInt(1000));
            } catch (InterruptedException e) {
            }
        }
    }
}

ServerThread.java--接受請求類

import java.util.Random;

public class ServerThread extends Thread {
    private Random random;
    private RequestQueue requestQueue;
    public ServerThread(RequestQueue requestQueue, String name, long seed) {
        super(name);
        this.requestQueue = requestQueue;
        this.random = new Random(seed);
    }
    public void run() {
        for (int i = 0; i < 10000; i++) {
            Request request = requestQueue.getRequest();
            System.out.println(Thread.currentThread().getName() + " 處理  " + request);
            try {
                Thread.sleep(random.nextInt(1000));
            } catch (InterruptedException e) {
            }
        }
    }
}