Java生产者与消费者（上）
本文来自http://blog.csdn.net/liuxian13183/ ，引用必须注明出处！
生产与消费者模式，是编程中最常用的模式之一，在多线程中应用比较明显。个人理解：在自助餐厅，厨师在不断做菜放桌子上，吃货不断从桌子上拿东西，这中间如果桌子上已经摆满那厨师要暂停工作 ，桌子上已没有食物则吃货要暂停拿东西吃。
先决条件，食材充足，桌子一定。
本程序设计原则：由于synchronized加锁方法，使得内部的所有变量也被加锁；我们采取多线程操作，故中间要用sleep（为了把锁让给别人，比如A上厕所开启sleep模式，B就偷偷拿上锁溜进来，方便后再还锁给A，要保证B修改同一个资源的话，要在A sleep的时间内完成），以便其他线程可以使用（windows多线程亦采取同样设计原则），sleep很短的时间，故用户不会有停滞感。为结果清晰，producer和consumer共执行操作50次，则程序停止运行。
桌子：
count，即桌子数量一定，produce和consume均对count操作。当蛋糕数大于等于桌子数时，生产线程要等待；当蛋糕数少于或等于0时，消费线程要等待。notifyAll是唤醒所有线程，如果生产线程watit时，消费线程已经把cake吃光，则要唤醒生产线程，反之亦然，故用notifyAll，而notify仅唤醒当前线程，在这里是没有用的。
public class Table {
private volatile int count;
private int cake;
private int stopCounts;
public Table(int count) {
// TODO Auto-generated constructor stub
this.count = count;
}
public synchronized void produce(String threadName) throws InterruptedException {
while (cake >= count) {
System.out.println(threadName + " begin to wait !");
wait();
System.out.println(threadName + " stop waiting !");
}
System.out.println(threadName + " produce:" + ++cake);
notifyAll();
if (++stopCounts > 50) {
System.out.println(threadName + " stop at last !");
System.exit(0);
}
}
public synchronized void consume(String threadName) throws InterruptedException {
while (cake <= 0) {
System.out.println(threadName + " begin to wait !");
wait();
System.out.println(threadName + " stop waiting !");
}
System.out.println(threadName + " consume:" + cake--);
notifyAll();
if (++stopCounts > 50) {
System.out.println(threadName + " stop at last !");
System.exit(0);
}
}
}
生产蛋糕，一次停止1毫秒
public class Producer extends Thread {
Table table;
String threadName;
public Producer(String string, Table table) {
// TODO Auto-generated constructor stub
this.table = table;
this.threadName=string;
this.setName(threadName);
}
@Override
public void run() {
// TODO Auto-generated method stub
super.run();
try {
while (true) {
table.produce(threadName);
sleep(1);
}
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
消费者：
消费蛋糕，一次停止1毫秒
public class Consumer extends Thread {
Table table;
String threadName;
public Consumer(String string, Table table) {
// TODO Auto-generated constructor stub
this.table = table;
this.threadName=string;
this.setName(threadName);
}
@Override
public void run() {
// TODO Auto-generated method stub
super.run();
try {
while (true) {
table.consume(threadName);
sleep(1);
}
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
验证程序：
多线程
public class TestCP {
public static void main(String[] args) {
Table table = new Table(5);
Thread p1 = new Producer("Produce1",table);
Thread c1 = new Consumer("Consumer1",table);
Thread p2 = new Producer("Produce2",table);
Thread c2 = new Consumer("Consumer2",table);
p1.start();
c1.start();
p2.start();
c2.start();
}
}
验证结果：
Produce1 produce:1 //Producer1先生产一只cake Produce2 produce:2 //Producer2得到锁生产一只 Consumer1 consume:2 //Consumer1先消费一只 Consumer2 consume:1 //Consumer2得到锁也消费一只 Consumer1 begin to wait ! //Consumer1得到锁开始等待 Produce1 produce:1 //Producer1开始生产 Produce2 produce:2 // Producer2开始生产 Consumer2 consume:2 //Consumer2开始消费 Consumer1 stop waiting ! //当cake数大于0，Consumer1停止等待 Consumer1 consume:1 //Consumer1开始消费 Consumer1 begin to wait ! //当cake数等于0，Consumer1开始等待 Consumer1 consume:1 //Consumer1开始消费 Consumer1 begin to wait ! //当cake数等于0，Consumer1开始等待 Produce2 produce:1 //.............................. Consumer1 stop waiting ! Consumer1 consume:1 Produce1 produce:1 Consumer2 consume:1 Consumer1 begin to wait ! Consumer2 begin to wait ! Produce1 produce:1 Produce2 produce:2 Consumer2 stop waiting ! Consumer2 consume:2 Consumer1 stop waiting ! Consumer1 consume:1 Consumer2 begin to wait ! Consumer1 begin to wait ! Produce1 produce:1 Consumer1 stop waiting ! Consumer1 consume:1 Consumer2 stop waiting ! Consumer2 begin to wait ! Produce2 produce:1 Consumer2 stop waiting ! Consumer2 consume:1 Consumer2 begin to wait ! Produce1 produce:1 Consumer1 consume:1 Consumer2 stop waiting ! Consumer2 begin to wait ! Produce2 produce:1 Consumer2 stop waiting ! Consumer2 consume:1 Produce1 produce:1 Produce2 produce:2 Consumer2 consume:2 Consumer1 consume:1 Consumer1 begin to wait ! Consumer2 begin to wait ! Produce1 produce:1 Produce2 produce:2 Consumer2 stop waiting ! Consumer2 consume:2 Consumer1 stop waiting ! Consumer1 consume:1 Consumer1 begin to wait ! Produce2 produce:1 Produce1 produce:2 Consumer1 stop waiting ! Consumer1 consume:2 Consumer2 consume:1 Consumer1 begin to wait ! Produce1 produce:1 Consumer2 consume:1 Produce2 produce:1 Consumer1 stop waiting ! Consumer1 consume:1 Consumer2 begin to wait ! Consumer1 begin to wait ! Produce1 produce:1 Consumer1 stop waiting ! Consumer1 consume:1 Consumer2 stop waiting ! Consumer2 begin to wait ! Produce2 produce:1 Consumer2 stop waiting ! Consumer2 consume:1 Consumer2 begin to wait ! Produce2 produce:1 Produce1 produce:2 Consumer1 consume:2 Consumer2 stop waiting ! Consumer2 consume:1 Consumer1 begin to wait ! Produce2 produce:1 Consumer1 stop waiting ! Consumer1 consume:1 Consumer2 begin to wait ! Produce1 produce:1 Produce1 stop at last !
需要拓展知识的请关注：