生产者--消费者模式

生产者--消费者模式

1、示例：

class Resource{
	private String name;
	private int count = 1;
	private Boolean flag = false;

	public synchronized void set(String name){
		if(flag)
			try {
				this.wait();//this代表调用函数线程
			} catch (InterruptedException e) {}

		this.name = name+"__ " + count++;
		System.out.println(Thread.currentThread().getName()+ "......生产者" + this.name);
		flag = true;
		this.notifyAll();
	}

	public synchronized void show(){
		if(!flag)
			try {
				this.wait();
			} catch (InterruptedException e) {
			}

		System.out.println(Thread.currentThread().getName()+"消费者"+ this.name);
		flag = false;
		this.notifyAll();
	}
}

//定义生产类Producter，生产商品

class Producter implements Runnable{
	private Resource r;
	Producter(Resource r){
		this.r = r;
	}
	public void run(){
		while(true){
			r.set("商品");
		}
	}
}

//定义消费者类Customer，消费商品
class Customer implements Runnable{
	private Resource r;
	Customer(Resource r){
		this.r = r;
	}
	public void run(){
		while(true){
			r.show();
		}
	}
}

分析：

• 多个生产者、消费者定义使用while判断标记

　　　　原因：让被唤醒的线程再次判断标记

• 定义中使用notifyAll

　　　　原因： 因为需要唤醒对方线程，如果使用notify容易出现值唤醒本方线程的情况，导致线程中所有线程都处于等待状态

2.JDK5中提供多线程解决方案

• 将同步synchronized替换成lock操作
• 将object中的wait/notify/notifyALl替换成condtion对象
• 该对象可以通过lock锁进行获取

示例：

package unit18;

import java.util.concurrent.locks.*;

class Resources{
	private String name;
	private int count = 1;
	private Boolean flag = false;

	private Lock lock = new ReentrantLock();//定义Lock类

	private Condition condition_pro = lock.newCondition();
	private Condition condition_con = lock.newCondition();

	public  void set(String name)throws InterruptedException{
		lock.lock();//添加锁
		try{
		while(flag){
			condition_pro.wait();//生产者调用线程等待
		  }
		this.name = name+"__ " + count++;
		System.out.println(Thread.currentThread().getName()+ "......生产者" + this.name);
		flag = true;
		condition_pro.signal();	//唤醒消费者线程
		}catch(Exception e){}
		finally{
			lock.unlock();//解锁
		}
	}

	public synchronized void show()throws InterruptedException{
		lock.lock();
		try{
		while(!flag){
			condition_con.wait();
		}

		System.out.println(Thread.currentThread().getName()+"消费者"+ this.name);
		flag = false;
		condition_con.signal();//唤醒生产者线程
		}catch(Exception e){}
		finally{
			lock.unlock();
		}
	}
}

class Producters implements Runnable{
	private Resources r;
	Producters(Resources r){
		this.r = r;
	}
	public void run(){
		while(true){
			try {
				r.set("商品");
			} catch (InterruptedException e) {

			}
		}
	}
}

class Customers implements Runnable{
	private Resources r;
	Customers(Resources r){
		this.r = r;
	}
	public void run(){
		while(true){
			try {
				r.show();
			} catch (InterruptedException e) {

			}
		}
	}
}

public class ProducterCustomerTest2 {

	public static void main(String[] args) {
		Resources r = new Resources();
		Producters pro = new Producters(r);
		Customers cus = new Customers(r);
		Thread t1 = new Thread(pro);
//		Thread t2 = new Thread(pro);
//		Thread t3 = new Thread(cus);
		Thread t2 = new Thread(cus);
		t1.start();
//		t2.start();
//		t3.start();
		t2.start();
	}

}