java 多线程 生产者-消费问题

//产品类
public class Product {
	
	private String productName;
	
	private int productNum;
	
	private int maxNum = 100;

	public String getProductName() {
		return productName;
	}

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

	public int getProductNum() {
		return productNum;
	}

	public void setProductNum(int productNum) {
		this.productNum = productNum;
	}

	public int getMaxNum() {
		return maxNum;
	}

	public void setMaxNum(int maxNum) {
		this.maxNum = maxNum;
	}
	
	
	
}

//生产者
public class Producer implements Runnable{
	
	public Product pro = null;
	public String  user = null;
	public Producer(Product pro,String user){
		this.pro = pro;
		this.user = user;
	}
	
	public void run() {
		while(true){
			synchronized (this) {
				if(pro.getProductNum() >= 20){
					try {
						System.out.println("仓库已满...");
						wait();
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
				}else{
					pro.setProductNum(pro.getProductNum()+1);
					System.out.println("生产了产品:  "+pro.getProductNum());
				}
			}
		}
		
	}
	
	
	
}

//消费者
public class Consumer implements Runnable{

	public Product pro = null;
	public String  user = null;
	public Consumer(Product pro,String user){
		this.pro = pro;
		this.user = user;
	}
	
	public void run() {
		while(true){
			synchronized (this) {
				if(pro.getProductNum() > 0){
					System.out.println("消费了产品:  "+pro.getProductNum());
					pro.setProductNum(pro.getProductNum()-1);
				}else{
					try {
						System.out.println("仓库已空...");
						wait();
					} catch (InterruptedException e) {
						e.printStackTrace();
					}
				}
			}
		}
	}
	
	
}

public class producerConsumerTest {
	
	public static void main(String[] args) {
		Product pro = new Product(); 
        Producer producer = new Producer(pro, "生产者"); 
        Consumer comsumer = new Consumer(pro, "消费者"); 
        Thread t1 = new Thread(producer); 
        Thread t2 = new Thread(comsumer); 
        t1.start(); 
        t2.start(); 
	}

	
}