Java多线程模式之Guarded Suspension Pattern

Guarded Suspension Pattern:保护暂停模式

 设计方法
  1。施加条件加以防卫
  2。区分等待和不等待的情况
  3。执行wait等待条件的变化

 参与者
  GuardedObject:被防卫的对象,有2个方法
   guardedMethod方法
    满足警戒条件时，马上执行
    不满足警戒条件时，等待
   stateChangingMethod方法
    更改警戒条件

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

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

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 + " ]";
    }
}


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();
    }
}

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

 

1. 将while改成if条件的问题

2.synchronized的范围只有wait

3.try..catch放在while 的外面

4.以Thread.sleep代替wait