Java多线程，消费问题

Java多线程，消费问题，下面代码问题在哪里
编写生产者消费者多线程程序，设有一个最大库存量为4的电视机仓库，生产10台电视机，一边生产一边销售（消费）。

public class Custom {
private int num = 0;
private int count;
public static void main(String[] args) {
Custom custom = new Custom();
Dc dc = custom.new Dc();
Ec ec = custom.new Ec();

	Thread thread = new Thread(dc);
	Thread thread1 = new Thread(ec);

	thread.setName("生产电视:");
	thread1.setName("销售1台电视，仓库还有:");

	thread.start();
	thread1.start();
}

class Dc implements Runnable {
	@Override
	public void run() {
		show();
	}

	private synchronized void show() {
		boolean flag = true;
		while (flag) {
			if (num > 3) {
				try {
					wait();
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			num++;
			System.out.println(Thread.currentThread().getName() + num + "台");
			count++;
			if (count == 10) {
				flag = false;
			}
			notifyAll();
		}
	}

}

class Ec implements Runnable {
	private synchronized void show(){
		while (true) {
			if (num < 1) {
				try {
					this.wait();
				} catch (InterruptedException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			num--;
			System.out.println(Thread.currentThread().getName() + num + "台");
			notifyAll();
		}
	}

	@Override
	public void run() {
		show();
	}
}
｝

Java多线程，消费