生产者与消费者问题中，关于对象监视器的问题

Question

 

在下面代码中如果我把生产者和消费者中的同步去掉，把同步shop代码块放在测试端里，为什么会报错，不是同样锁定同步shop对象嘛？

import java.util.Stack;

public class Shop {
    Stack<Integer> stack = new Stack<Integer>();
    
    public boolean empty(){
        return this.stack.empty();
    }
    public Integer peek(){
        return this.stack.peek();
    }
    public Integer pop(){
        return this.stack.pop();
    }
    public Integer push(Integer i){
        return this.stack.push(i) ;
    }
    public  int serach(Integer i){
        return this.stack.search(i) ;
    }
}

 public class Seller extends Thread{

 

 private Shop shop ;
    public Seller(Shop shop){
        this.shop = shop ;
    }
    public void run(){
        synchronized(shop){
            for (int i = 1 ; i <= 30 ; i++) {
                System.out.println( "商店生产了："+shop.push(new Integer(i))+" 号部件。 " );
                shop.notifyAll() ;
                try {
                    shop.wait() ;
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }   
    }
}

 public class Buyer extends Thread {

 private Shop shop ;
    public Buyer(Shop shop){
        this.shop = shop ;
    }
    public void run(){
        synchronized(shop){
            for(int i=1 ; i<= 30 ; i++){
                while(shop.empty()){
                    try {
                        shop.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                System.out.println("顾客买走了编号为："+shop.pop()+" 号零件");
                shop.notify() ;
            }
        }
    }
}

 public class Client {

   public static void main(String[] args) {
        Shop shop = new Shop() ;
        Seller seller = new Seller(shop) ;
        Buyer buyer = new Buyer(shop) ;

//     synchronized(shop){
            seller.start() ;
            buyer.start() ;

//     }
    }

}

Answer 1

我在里面使用，你在外边同步，木有作用