多线程设计模式之——Producer-Consumer Pattern

此模式是在生产者与消费者之间加入一个“桥梁参与者”来缓冲线程之间的处理速度差。一般可以存在多个生产者与消费者，但当双方都只有一个的时候，又称为Pipe Pattern。

例子：假设有2个生产者,2个消费者，仓库里只能放4个产品。(这里的产品就是String类型的名字而已)

//Storage.java
public class Storage {
	private String[] buffer;
	private int head;//取走一个商品的位置
	private int tail;//存入一个商品的位置
	private int count;//buffer内的商品数量
	
	public Storage(int count){
		this.buffer = new String[count];
		this.count = 0;
		this.head = 0;
		this.tail = 0;
	}
	
	//这里的if警戒条件就运用了Guarded Suspension Pattern，要求不满足条件，便等待
	public synchronized void put(String goods) throws InterruptedException{
		System.out.println(Thread.currentThread().getName() + " produce the goods:" + goods);
		if(count >= buffer.length){
			System.out.println("the storage is full!");
			wait();
		}
		buffer[tail] = goods;
		tail = (tail + 1) % buffer.length;
		count++;
		notifyAll();
	}
	
	public synchronized String get() throws InterruptedException{
		if(count <= 0){
			System.out.println("the storage is empty!");
			wait();
		}
		String goods = buffer[head];
		head = (head + 1) % buffer.length;
		count--;
		notifyAll();
		System.out.println(Thread.currentThread().getName() + " consume the goods:" + goods );
		return goods;
	}

}

//ProducerThread.java
import java.util.Random;


public class ProducerThread extends Thread {
	private Storage storage;
	private Random random;
	private static int pid;  //产品编号
	
	public ProducerThread(String name , Storage storage){
		super(name);
		this.storage = storage;
		this.random = new Random();
	}
	
	public void run(){
		try{
			for(int i=0; i<10; i++){
				Thread.sleep(random.nextInt(1000));//模拟生产时间
				String goods = getName() + " produce the goods" + nextPId();
				storage.put(goods);
			}
		}catch(InterruptedException e){
			e.printStackTrace();
		}
	}
	
	private static synchronized int nextPId(){
		return pid++;
	}

}

//ConsumerThread.java
import java.util.Random;


public class ConsumerThread extends Thread {
	private Storage storage;
	private Random random;
	
	public ConsumerThread(String name , Storage storage){
		super(name);
		this.random = new Random();
		this.storage = storage;
	}
	
	public void run(){
		try{
			while(true){
				storage.get();
				Thread.sleep(random.nextInt(2000));//模拟商品使用时间
			}
		}catch(InterruptedException e){
			e.printStackTrace();
		}
	}

}

//Main.java
public class Main {

	public static void main(String[] args) {
		Storage storage = new Storage(4);
		new ProducerThread("producer_lulu01" , storage).start();
		new ProducerThread("producer_lulu02" , storage).start();
		new ConsumerThread("consumer_fang01" , storage).start();
		new ConsumerThread("consumer_fang02" , storage).start();
		

	}

}