一个多线程小程序

今天看见一个多线程问题，心里痒痒，就做了做，然后就有了这么一个小程序。

问题在这里：[url]http://www.iteye.com/problems/46763[/url]

有三方：厂家，电脑城，顾客
厂家2个，一个生产主板，一个生产显卡。
顾客有2个，他们各自不断购买主板和显卡。
电脑城有一个，卖显卡和主板。

货品类，方便调试：

public class Product {
    private String name;
    private int serial;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getSerial() {
        return serial;
    }

    public void setSerial(int serial) {
        this.serial = serial;
    }
}

货品供需管理类，多线程调度的核心：

import java.util.ArrayDeque;

public class StockManager {
    private final Object producerLock = new Object();
    private final Object consumerLock = new Object();
    private final int MAX_SIZE = 10;

    private final ArrayDeque queue = new ArrayDeque();

    public void stock(Product p) throws InterruptedException {
        synchronized (producerLock) {
            if (queue.size() >= MAX_SIZE) {
                producerLock.wait();
            }
        }
        synchronized (queue) {
            queue.add(p);
        }
        synchronized (consumerLock) {
            consumerLock.notify();
        }
    }

    public synchronized Product purchase() throws InterruptedException {
        synchronized (consumerLock) {
            if (queue.size() <= 0) {
                consumerLock.wait();
            }
        }
        Product product = null;
        synchronized (queue) {
            product = queue.remove();
        }
        synchronized (producerLock) {
            producerLock.notify();
        }
        return product;
    }
}

厂商类，可以生产产品，另有一个run，用于实现具体的生产过程，以调节测试时的供求关系：

import java.util.logging.Logger;

public class Producer implements Runnable{
    private static final Logger log = Logger.getLogger(Producer.class.getName());

    private String productName = null;
    private int serial = 0;
    private StockManager stockManager;

    public void setProductName(String productName) {
        this.productName = productName;
    }

    public void setStockManager(StockManager stockManager) {
        this.stockManager = stockManager;
    }

    public Product produce() {
        final Product p = new Product();
        p.setName(productName);
        p.setSerial(++serial);
        return p;
    }

    @Override
    public void run() {
        try {
            for( int i = 0; i < 20; i++) {
                deliver();
            }
            Thread.sleep(30 * 1000);
            while (true) {
                deliver();
            }
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }

    private void deliver() throws InterruptedException {
        final long s = System.currentTimeMillis();
        final Product product = produce();
        stockManager.stock(product);
        final long time = System.currentTimeMillis() - s;
        if (time > 10) {
            log.info(product.getName() + ", No. " +
                    product.getSerial() + " took " +
                    time + " milli seconds to finish." );
        }
    }
}

客户类，比较简单，外加调试信息：

import java.util.logging.Logger;

public class Consumer implements Runnable {
    private static final Logger log = Logger.getLogger(Consumer.class.getName());

    private String name;
    private StockManager[] stockManagers;

    public void setName(String name) {
        this.name = name;
    }

    public void setStockManagers(StockManager[] stockManagers) {
        this.stockManagers = stockManagers;
    }

    @Override
    public void run() {
        for (int i = 0; i < 50; i++) {
            final double v = Math.random() * stockManagers.length;
            final int k = (int) Math.floor(v);
            try {
                final long s = System.currentTimeMillis();
                final Product product = stockManagers[k].purchase();
                final long time = System.currentTimeMillis() - s;
                String l = "";
                if (time > 10) {
                    l += "after " + time + " milli seconds of waiting, ";
                }
                l += (name + " bought product " + product.getName()
                        + ", serial No. " + product.getSerial());
                log.info(l);
            } catch (InterruptedException e) {
                e.printStackTrace();
                break;
            }

            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
                break;
            }
        }
    }
}

程序入口，初始化上述各类，启动相应线程：

public class Mall {
    public static void main(String[] args) {
        final StockManager mb = new StockManager();
        final Producer pmb = new Producer();
        pmb.setProductName("Motherboard");
        pmb.setStockManager(mb);

        final StockManager vd = new StockManager();
        final Producer pvd = new Producer();
        pvd.setProductName("Video Card");
        pvd.setStockManager(vd);

        final StockManager[] stockManagers = new StockManager[2];
        stockManagers[0] = mb;
        stockManagers[1] = vd;

        final Consumer c1 = new Consumer();
        c1.setName("C1");
        c1.setStockManagers(stockManagers);

        final Consumer c2 = new Consumer();
        c2.setName("C2");
        c2.setStockManagers(stockManagers);

        final Thread tc1 = new Thread(c1);
        tc1.start();
        final Thread tc2 = new Thread(c2);
        tc2.start();

        try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        new Thread(pmb).start();
        new Thread(pvd).start();

        try {
            tc1.join();
            tc2.join();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        // kill system after consumer done shopping
        System.exit(0);
    }
}

感觉StockManager还是有些问题，但是又说不清楚。