[Java] 生产者&消费者问题

于 2012-07-24 18:00:19 发布
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本文链接：https://blog.youkuaiyun.com/sodino/article/details/7781626
本文介绍了一个简单的生产者消费者模式实现，使用Java语言并通过synchronized关键字确保线程间的同步。该程序实现了生产者向仓库添加商品，消费者从仓库移除商品的过程，同时限制了仓库的最大容量及生产的商品数量。

无聊，想起还没自己实现过。写了个。备忘。

生产者&消费者问题描述

有一个生产者线程在生产产品，并放入仓库，另有一消费者线程从仓库中取出产品进行消费。
这个过程可以是无休止的，不能因为仓库已满生产者放不进产品而终止，也不能因为仓库中没有产品了消费者停止消费。

本例子采用使生产者与消费者之间的保持同步的方式实现此功能。当生产者生产的产品放入仓库时，会通知消费者可以进行消费了，如果放满了仓库则生产者暂时放弃自己的执行权，进入等待状态等待消费者消费产品;消费者从仓库中消费产品，如果发现仓库已空，则进入等待状态等待生产者生产新产品，并且每消费一件产品则通知生产者生产。

由程序最后的打印输出可看出，从“通知”到生产者/消费者真正执行生产/消费操作的时机也是不固定的。

下面是代码：

package lab.sodino.pc;

import java.util.LinkedList;

/**
 * @author Sodino E-mail:sodinoopen@hotmail.com
 * @version Time：2012-7-24 下午04:25:47
 */
public class Sync {
	/** 仓库。 */
	private LinkedList<Goods> list;
	/** 仓库最多存储10产品。 */
	public static final int CAPABILITY = 10;
	/** 限制只生产/消费100个产品，然后结束运行。 */
	public static final int MAX_AMOUNT = 100;

	public static void main(String[] args) {
		Sync sync = new Sync();
		sync.run();
	}

	public void run() {
		list = new LinkedList<Goods>();

		new Product().start();
		new Consume().start();
	}

	/**
	 * 生产者：<br/>
	 * 1.负责生产产品；<br/>
	 * 2.生产出产品后负责通知消费者线程消费；<br/>
	 * 3.库存为MAX时，暂停生产；<br/>
	 * 4.每次只生产一件产品。<br/>
	 */
	class Product extends Thread {
		int goodsIdx = 0;

		public void run() {
			try {
				while (true) {
					if (goodsIdx > MAX_AMOUNT) {
						break;
					}
					synchronized (list) {
						while (list.size() == CAPABILITY) {
							if (list.size() == CAPABILITY) {
								System.out.println("Product		Goodses's Amount is full.  wait");
								// 等待消费者消费才有空间腾出给新生产的产品
								list.wait();
							}
						}

						Goods goods = new Goods(goodsIdx++);
						if (list.add(goods)) {
							System.out.println("Product		new[" + String.valueOf(goods) + "]");
							// 通知消费者消费
							list.notify();
						}
					}
				}
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}

	/**
	 * 消费者：<br/>
	 * 1.一次只消费一个产品；<br/>
	 * 2.消费完产品后负责通知生产者继续生产。<br/>
	 * */
	class Consume extends Thread {
		public void run() {
			try {
				while (true) {
					synchronized (list) {
						while (list.size() == 0) {
							System.out.println("Consume		There's no goods,wait...");
							// 等待生产者生产
							list.wait();
						}
						Goods goods = list.remove(0);
						System.out.println("Consume		remove[" + String.valueOf(goods) + "]");
						if (goods.getIndex() < MAX_AMOUNT) {
							// 通知生产者继续生产
							list.notify();
						} else {
							System.out.println("List.size=" + list.size());
							break;
						}
					}
				}
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		}
	}
}

package lab.sodino.pc;

/**
 * @author Sodino E-mail:sodinoopen@hotmail.com
 * @version Time：2012-7-24 下午04:25:47
 */
public class Goods {
	private int index;

	public Goods(int idx) {
		index = idx;
	}

	public int getIndex() {
		return index;
	}

	public String toString() {
		String line = "Goods id:" + Integer.toString(index);
		return line;
	}
}

输出： 

Consume		There's no goods,wait...
Product		new[Goods id:0]
Consume		remove[Goods id:0]
Consume		There's no goods,wait...
Product		new[Goods id:1]
Consume		remove[Goods id:1]
Consume		There's no goods,wait...
Product		new[Goods id:2]
Consume		remove[Goods id:2]
Consume		There's no goods,wait...
Product		new[Goods id:3]
Consume		remove[Goods id:3]
Consume		There's no goods,wait...
Product		new[Goods id:4]
Consume		remove[Goods id:4]
Consume		There's no goods,wait...
Product		new[Goods id:5]
Consume		remove[Goods id:5]
Consume		There's no goods,wait...
Product		new[Goods id:6]
Consume		remove[Goods id:6]
Consume		There's no goods,wait...
Product		new[Goods id:7]
Consume		remove[Goods id:7]
Consume		There's no goods,wait...
Product		new[Goods id:8]
Consume		remove[Goods id:8]
Consume		There's no goods,wait...
Product		new[Goods id:9]
Consume		remove[Goods id:9]
Consume		There's no goods,wait...
Product		new[Goods id:10]
Product		new[Goods id:11]
Product		new[Goods id:12]
Product		new[Goods id:13]
Product		new[Goods id:14]
Product		new[Goods id:15]
Product		new[Goods id:16]
Product		new[Goods id:17]
Product		new[Goods id:18]
Product		new[Goods id:19]
Product		Goodses's Amount is full.  wait
Consume		remove[Goods id:10]
Consume		remove[Goods id:11]
Consume		remove[Goods id:12]
Consume		remove[Goods id:13]
Consume		remove[Goods id:14]
Consume		remove[Goods id:15]
Consume		remove[Goods id:16]
Consume		remove[Goods id:17]
Consume		remove[Goods id:18]
Consume		remove[Goods id:19]
Consume		There's no goods,wait...
Product		new[Goods id:20]
Product		new[Goods id:21]
Product		new[Goods id:22]
Product		new[Goods id:23]
Product		new[Goods id:24]
Product		new[Goods id:25]
Product		new[Goods id:26]
Product		new[Goods id:27]
Product		new[Goods id:28]
Product		new[Goods id:29]
Product		Goodses's Amount is full.  wait
Consume		remove[Goods id:20]
Consume		remove[Goods id:21]
Consume		remove[Goods id:22]
Consume		remove[Goods id:23]
Consume		remove[Goods id:24]
Consume		remove[Goods id:25]
Consume		remove[Goods id:26]
Consume		remove[Goods id:27]
Consume		remove[Goods id:28]
Consume		remove[Goods id:29]
Consume		There's no goods,wait...
Product		new[Goods id:30]
Product		new[Goods id:31]
Product		new[Goods id:32]
Product		new[Goods id:33]
Product		new[Goods id:34]
Product		new[Goods id:35]
Product		new[Goods id:36]
Product		new[Goods id:37]
Product		new[Goods id:38]
Product		new[Goods id:39]
Product		Goodses's Amount is full.  wait
Consume		remove[Goods id:30]
Consume		remove[Goods id:31]
Consume		remove[Goods id:32]
Consume		remove[Goods id:33]
Consume		remove[Goods id:34]
Consume		remove[Goods id:35]
Consume		remove[Goods id:36]
Consume		remove[Goods id:37]
Consume		remove[Goods id:38]
Consume		remove[Goods id:39]
Consume		There's no goods,wait...
Product		new[Goods id:40]
Product		new[Goods id:41]
Product		new[Goods id:42]
Product		new[Goods id:43]
Product		new[Goods id:44]
Product		new[Goods id:45]
Product		new[Goods id:46]
Product		new[Goods id:47]
Product		new[Goods id:48]
Product		new[Goods id:49]
Product		Goodses's Amount is full.  wait
Consume		remove[Goods id:40]
Consume		remove[Goods id:41]
Consume		remove[Goods id:42]
Consume		remove[Goods id:43]
Consume		remove[Goods id:44]
Consume		remove[Goods id:45]
Consume		remove[Goods id:46]
Consume		remove[Goods id:47]
Consume		remove[Goods id:48]
Consume		remove[Goods id:49]
Consume		There's no goods,wait...
Product		new[Goods id:50]
Product		new[Goods id:51]
Product		new[Goods id:52]
Product		new[Goods id:53]
Product		new[Goods id:54]
Product		new[Goods id:55]
Product		new[Goods id:56]
Product		new[Goods id:57]
Product		new[Goods id:58]
Product		new[Goods id:59]
Product		Goodses's Amount is full.  wait
Consume		remove[Goods id:50]
Consume		remove[Goods id:51]
Consume		remove[Goods id:52]
Product		new[Goods id:60]
Product		new[Goods id:61]
Product		new[Goods id:62]
Product		Goodses's Amount is full.  wait
Consume		remove[Goods id:53]
Consume		remove[Goods id:54]
Consume		remove[Goods id:55]
Consume		remove[Goods id:56]
Consume		remove[Goods id:57]
Consume		remove[Goods id:58]
Consume		remove[Goods id:59]
Consume		remove[Goods id:60]
Consume		remove[Goods id:61]
Consume		remove[Goods id:62]
Consume		There's no goods,wait...
Product		new[Goods id:63]
Product		new[Goods id:64]
Product		new[Goods id:65]
Product		new[Goods id:66]
Product		new[Goods id:67]
Product		new[Goods id:68]
Product		new[Goods id:69]
Product		new[Goods id:70]
Product		new[Goods id:71]
Product		new[Goods id:72]
Product		Goodses's Amount is full.  wait
Consume		remove[Goods id:63]
Consume		remove[Goods id:64]
Consume		remove[Goods id:65]
Consume		remove[Goods id:66]
Consume		remove[Goods id:67]
Consume		remove[Goods id:68]
Consume		remove[Goods id:69]
Consume		remove[Goods id:70]
Consume		remove[Goods id:71]
Consume		remove[Goods id:72]
Consume		There's no goods,wait...
Product		new[Goods id:73]
Product		new[Goods id:74]
Product		new[Goods id:75]
Product		new[Goods id:76]
Product		new[Goods id:77]
Product		new[Goods id:78]
Product		new[Goods id:79]
Product		new[Goods id:80]
Product		new[Goods id:81]
Product		new[Goods id:82]
Product		Goodses's Amount is full.  wait
Consume		remove[Goods id:73]
Consume		remove[Goods id:74]
Product		new[Goods id:83]
Product		new[Goods id:84]
Product		Goodses's Amount is full.  wait
Consume		remove[Goods id:75]
Consume		remove[Goods id:76]
Consume		remove[Goods id:77]
Consume		remove[Goods id:78]
Consume		remove[Goods id:79]
Consume		remove[Goods id:80]
Consume		remove[Goods id:81]
Consume		remove[Goods id:82]
Consume		remove[Goods id:83]
Consume		remove[Goods id:84]
Consume		There's no goods,wait...
Product		new[Goods id:85]
Product		new[Goods id:86]
Product		new[Goods id:87]
Product		new[Goods id:88]
Product		new[Goods id:89]
Product		new[Goods id:90]
Product		new[Goods id:91]
Product		new[Goods id:92]
Product		new[Goods id:93]
Product		new[Goods id:94]
Product		Goodses's Amount is full.  wait
Consume		remove[Goods id:85]
Product		new[Goods id:95]
Product		Goodses's Amount is full.  wait
Consume		remove[Goods id:86]
Consume		remove[Goods id:87]
Consume		remove[Goods id:88]
Consume		remove[Goods id:89]
Consume		remove[Goods id:90]
Consume		remove[Goods id:91]
Product		new[Goods id:96]
Product		new[Goods id:97]
Product		new[Goods id:98]
Product		new[Goods id:99]
Product		new[Goods id:100]
Consume		remove[Goods id:92]
Consume		remove[Goods id:93]
Consume		remove[Goods id:94]
Consume		remove[Goods id:95]
Consume		remove[Goods id:96]
Consume		remove[Goods id:97]
Consume		remove[Goods id:98]
Consume		remove[Goods id:99]
Consume		remove[Goods id:100]
List.size=0



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