java进程通信问题求助 - 编程论坛

程序代码：

package ThreadTest;

import java.util.ArrayList;
import java.util.List;

public class FirstThread {
    static List<Object> goods = new ArrayList<>();    //储存物品的仓库，最多储存1
    public static void main(String[] args) throws InterruptedException {
        Producer thread1 = new Producer();
        Consumer thread2 = new Consumer();

        Thread p1 = new Thread(thread1, "生产者1");
        Thread p2 = new Thread(thread1, "生产者2");
        Thread p3 = new Thread(thread1, "生产者3");
        Thread c1 = new Thread(thread2, "消费者1");
        Thread c2 = new Thread(thread2, "消费者2");
        Thread c3 = new Thread(thread2, "消费者3");

        p1.start();
        p2.start();
        p3.start();
        c1.start();
        c2.start();
        c3.start();

}
    static class Producer implements Runnable {

        @Override
        public void run() {
            // TODO Auto-generated method stub
            int num = 0;
            while(true) {
                synchronized (goods) {
                    if(goods.size()==0) {
                        goods.add("商品" + ++num);
                        System.out.println(Thread.currentThread().getName()+"生产了第"+num+"个产品");
                    }
                    else if(goods.size()>0)
                        try {
                            goods.wait();
                        } catch (InterruptedException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                }
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }
}
    static class Consumer implements Runnable {

        @Override
        public void run() {
            // TODO Auto-generated method stub
            int num = 0;
            while(true) {
                synchronized (goods) {
                    if(goods.size()>0) {
                        goods.remove("商品"+ ++num);
                        System.out.println(Thread.currentThread().getName()+"消费了第"+num+"个产品");
                    }
                    else if (goods.size()==0)
                        goods.notify();;
                }
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
            }
        }

    }
}

为什么所有的生产者不是共用一个num,输出时每个生产者都会输出1，2...。我按照书上的例子可以实现共享，是不是这里是内部类的问题，但是如果不用内部类我又怎么实现生产者和消费者之间的通信呢，
顺便再问一个问题，那就是我按照书上的例子敲的，但是每次执行的结果都是几乎由一个窗口完成全部售票，没有达到上下两张票的窗口一定不同，代码如下：
按理来说sleep(100)会保证不让同一线程连续执行

程序代码：

package ThreadTest;

class SaleThread2 implements Runnable {
    int tickets = 10;
    Object lock = new Object();
    @Override
    public void run() {
        // TODO Auto-generated method stub
        while(true) {
            synchronized (lock) {
                if(tickets>0) {
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName()+"正在出售第"+tickets-- +"张票");
                }
            }
        }
    }

}

public class Example12 {
    public static void main(String[] args) {
        SaleThread2 st = new SaleThread2();
        new Thread(st, "窗口1").start();
        new Thread(st, "窗口2").start();
        new Thread(st, "窗口3").start();
        new Thread(st, "窗口4").start();
    }
}