Java 线程同步问题 生产者-消费者 算法实现 -Java学习笔记（29）

我们晦涩的操作系统课本也讲过 生产者-消费者问题，不过是由Pascal写的用来解决 进程 同步的，不幸的是我并没学过Pascal。考试时大家都是用C语言写的，但是我极其怀疑这些应试程序段能不能拿到项目中应用。
课本上的算法是有信号量机制实现的（不要问我什么是信号量，课本上没讲）。声明一个int变量mutex（信号量），调用wait()     signal()方法 。
wait(mutex);   // if(mutex==0) { 阻塞当前进程; } else ( mutex--; }  
signal(mutex);    // mutex++;  唤醒wait进程

Java中似乎没有类似的方法，java中线程同步是由Object的方法wait()   notify() / notifyAll()  实现的。这些方法必须在同步块（Critical Section 关键字synchronized）中。
我们知道synchronized (Object o) 是拿走对象o所拥有的唯一的钥匙（具体见我的另外一篇博客http://blog.youkuaiyun.com/nyzhl/archive/2007/05/19/1617014.aspx），
而o.wait()的作用就是阻塞当前线程并且释放对象o的钥匙
o.notify()/notifyAll()的作用是唤醒对象o   wait阻塞的线程，重新竞争o的钥匙。

Thead.sleep()也是阻塞当前线程，但不释放钥匙

下面是我的程序源代码，3个生产者Alice,Bob,Lucy他们向只能放一个产品的容器里放产品  2个消费者James,Charlie。他们从容器里拿产品

/**/ /* 消费者生产者线程演示
 * Coding by ZhaoHongliang.
**/
public   class  ProducerConsumer  ... {
    public static void main(String[] args) ...{
        Container container = new Container();
        Producer Alice = new Producer("Alice",container);
        Thread produceThread1 = new Thread(Alice);
        produceThread1.start();
        Producer Bob = new Producer("Bob",container);
        Thread produceThread2 = new Thread(Bob);
        produceThread2.start();
        Producer Lucy = new Producer("Lucy",container);
        Thread produceThread3 = new Thread(Lucy);
        produceThread3.start();
        Consumer James = new Consumer("James",container);
        Thread consumeThread1 = new Thread(James);
        consumeThread1.start();
        Consumer Charlie = new Consumer("Charlie",container);
        Thread consumeThread2 = new Thread(Charlie);
        consumeThread2.start();
    }
}
/**/ /* 生产者 */
class  Producer  implements  Runnable  ... {
    private String name;
    private Container container = null;
    //Constructor
    public Producer(String producerName,Container container) ...{
        this.name = producerName;
        this.container = container;
    }
    //Override abstract methoed of Interface Runnable.
    public void run() ...{
        while(true) ...{
            synchronized(this.container) ...{
                while(!this.container.isEmpty()) ...{
                    try ...{
                        this.container.wait();
                    }
                    catch (InterruptedException e) ...{
                        e.printStackTrace();
                    }
                }
                Product pushedProduct = new Product(this.name);
                container.push(pushedProduct);
                try ...{
                    Thread.sleep((int)(Math.random()*2000));
                }
                catch (InterruptedException e) ...{
                    e.printStackTrace();
                }
                this.container.notifyAll();
            }
        }
    }
}
/**/ /* 消费者 */
class  Consumer  implements  Runnable  ... {
    private String name;
    private Container container = null;
    //Constructor
    public Consumer(String consumerName,Container container) ...{
        this.name = consumerName;
        this.container = container;
    }
    //Override abstract methoed of Interface Runnable.
    public void run() ...{
        while(true) ...{
            synchronized (this.container) ...{
                while(this.container.isEmpty()) ...{
                    try ...{
                        this.container.wait();
                    }
                    catch (InterruptedException e) ...{
                        e.printStackTrace();
                    }
                }
                Product popedProduct = container.pop(name);
                try ...{
                    Thread.sleep((int)(Math.random()*1000));
                }
                catch (InterruptedException e) ...{
                    e.printStackTrace();
                }
                this.container.notifyAll();
            }
        }
    }
}
/**/ /* 产品 */
class  Product  ... {
    private static int id = 0;
    //Constructor
    private String producerName;
    public Product(String producerName) ...{
        this.producerName = producerName;
        this.id ++;
    }
    //Override method of Class Object.
    public String toString() ...{
        return "Product No."+id+"; Made by "+producerName;
    }
}
/**/ /* 容器 只允许放一个产品 */
class  Container  ... {
    private Product container = null;
    //Test if the container is empty.
    public boolean isEmpty() ...{
        if (this.container==null) ...{
            return true;
        }
        else ...{
            return false;
        }
    }
    public synchronized void push(Product product) ...{
        if (this.isEmpty()) ...{
            this.container = product;
            System.out.println("Pushed: "+product);
        }
        else ...{
            throw new RuntimeException("Can't push! The container is full.");
        }
    }
    public synchronized Product pop(String consumerName) ...{
        if (!this.isEmpty()) ...{
            Product temp = this.container;
            this.container = null;
            System.out.println(consumerName+" poped: "+temp);
            return temp;
        }
        else ...{
            throw new RuntimeException("Can't pop! The container is empty.");
        }
    } 
}

运行结果（死循环）
Pushed: Product No.1; Made by Alice
Charlie poped: Product No.1; Made by Alice
Pushed: Product No.2; Made by Lucy
James poped: Product No.2; Made by Lucy
Pushed: Product No.3; Made by Alice
Charlie poped: Product No.3; Made by Alice
Pushed: Product No.4; Made by Bob
James poped: Product No.4; Made by Bob
Pushed: Product No.5; Made by Alice
Charlie poped: Product No.5; Made by Alice
Pushed: Product No.6; Made by Lucy
James poped: Product No.6; Made by Lucy
Pushed: Product No.7; Made by Alice
Charlie poped: Product No.7; Made by Alice
Pushed: Product No.8; Made by Bob
James poped: Product No.8; Made by Bob
Pushed: Product No.9; Made by Alice
Charlie poped: Product No.9; Made by Alice
Pushed: Product No.10; Made by Lucy
James poped: Product No.10; Made by Lucy
。。。 。。。