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();	}}