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)

Java代码

//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;
}

}

Java代码

//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++;
}

}

Java代码

//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();
}
}

}

Java代码

//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();


}

}