生产者消费者模式

生产者生产速度和消费者消费速度不平衡，利用一个阻塞队列实现缓冲区，比如，如果生产者速度较快，当队列已满，就不再生产。同理，队列空的时候，消费者不再消费进入睡眠等到生产者有生产的时候才开始消费。所以

1. 这个模式实现了平衡两者间处理能力
2. 实现生产者和消费者逻辑间解耦


import java.util.Stack;
import java.util.concurrent.atomic.AtomicInteger;

/**
 * 1个生产者 3个消费者 生产、消费10次
 *
 * @作者 pt
 *
 */

public class ProducerConsumer {
Stack<Integer> items = new Stack<Integer>();
final static int NO_ITEMS = 10;

public static void main(String args[]) {
ProducerConsumer pc = new ProducerConsumer();
                Thread t1 = new Thread(pc.new Producer());
                Consumer consumer  = pc.new Consumer();

Thread t2 = new Thread(consumer);
Thread t3 = new Thread(consumer);
Thread t4 = new Thread(consumer);
t1.start();
try {
Thread.sleep(100);
} catch (InterruptedException e1) {
e1.printStackTrace();
}
t2.start();
t3.start();
t4.start();
try {
t2.join();
t3.join();
t4.join();
} catch (InterruptedException e) {
e.printStackTrace();
}
}

class Producer implements Runnable {
public void produce(int i) {
System.out.println("Producing " + i);
items.push(new Integer(i));
}

@Override
public void run() {
int i = 0;
// 生产10次
while (i++ < NO_ITEMS) {
synchronized (items) {
produce(i);
items.notifyAll();
}
try {
// 休眠一段时间
Thread.sleep(1000);
} catch (InterruptedException e) {
}
}
}
}

class Consumer implements Runnable {
                // consumed计数器允许线程停止
AtomicInteger consumed = new AtomicInteger();

public void consume() {
if (!items.isEmpty()) {
System.out.println(Thread.currentThread().getId()+" Consuming " + items.pop());
consumed.incrementAndGet();
}
}

private boolean theEnd() {
return consumed.get() >= NO_ITEMS;
}

@Override
public void run() {
while (!theEnd()) {
synchronized (items) {
while (items.isEmpty() && (!theEnd())) {
try {
//wait same time as Producer, 主要目的是sleep，减少CPU资源消耗
items.wait(1000);
} catch (InterruptedException e) {
Thread.interrupted();
}
}
consume();

}
}
}
}
}

ref: https://zh.wikipedia.org/wiki/%E7%94%9F%E4%BA%A7%E8%80%85%E6%B6%88%E8%B4%B9%E8%80%85%E9%97%AE%E9%A2%98
http://www.infoq.com/cn/articles/producers-and-consumers-mode