线程之旅--Guarded Suspension Pattern

在家换衣服时，突然门铃响了，原来邮递员送快递了。因为衣服不能换了一半就出去，所以对邮递员将，请您稍等。在把门打开，说“让您久等了”，Guarded Suspension Pattern 就是适合这种情况的

下面我们用个简单的例子来进行说明（范例由5个文件组成）： 大家在要注意为什么要加synchronized ，它想保护的究竟是什么，为什么要wait，为什么put后要nitifyAll();

Main.java--调用类

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

Request.java--请求类

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--请求队列

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--送出请求类

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() + " 送出请求 " + request);
            requestQueue.putRequest(request);
            try {
                Thread.sleep(random.nextInt(1000));
            } catch (InterruptedException e) {
            }
        }
    }
}

ServerThread.java--接受请求类

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() + " 处理  " + request);
            try {
                Thread.sleep(random.nextInt(1000));
            } catch (InterruptedException e) {
            }
        }
    }
}