老师，能帮我调试一下代码看看为什么在购物车中添加新的商品时会把之前的商品信息覆盖

package com.imooc;

import java.util.HashMap;

import java.util.Map.Entry;

import java.util.Scanner;

import java.util.Set;

/*

 * 

 * 购物车类（ShoppingCart）

属性：

－ 购物车（shoppingCart）:Map类型，其中key为String类型，value为GoodsInCart类型

方法：

－添加商品到购物车：

   public void addGoodsToCart(GoodsManage gm);

－修改购物车中的商品数量：public void updateNumInCart();

 - 显示购物车中的所有商品：public void displayAllInCart();

 - 结算：public void settleAccounts();

 - 构造方法及getter和setter方法

 * 

 * */

public class ShoppingCart {

private HashMap<String,GoodsInCart> shoppingCart;

private ShoppingCart() {

}

private ShoppingCart(HashMap<String, GoodsInCart> shoppingCart) {

super();

this.shoppingCart = shoppingCart;

}

//创建对象

static ShoppingCart  shoppingcart= null;

public static ShoppingCart getInstance() {

if(shoppingcart == null) {

shoppingcart = new ShoppingCart();

return  shoppingcart;

}

return  shoppingcart;

}

public HashMap<String, GoodsInCart> getShoppingCart() {

return shoppingCart;

}

public void setShoppingCart(HashMap<String, GoodsInCart> shoppingCart) {

this.shoppingCart = shoppingCart;

}

HashMap<String,GoodsInCart> map = new HashMap<>();

//－添加商品到购物车：

   public void addGoodsToCart(GoodsManage gm) {

   try {

Scanner input = new Scanner(System.in);

Set<Goods> goodsset = gm.getGoodsSet();

//System.out.println(goodsset.size());

   if(goodsset.size() == 0) {

   System.out.println("商品未导入！");

   }else {

    //库中有商品，

   System.out.print("请输入商品编号：");

   String goodsId = input.next();

   //System.out.println(goodsId);

   for (Goods goods : goodsset) {

   //去判断输入的商品ID是否在库中存在

   String goodsid = goods.getGoodsId();

   if(goodsid.equals(goodsId)) {

   if(shoppingcart.getShoppingCart() == null) {

   System.out.println("购物车中还没有商品哦");

   GoodsInCart goodsincart = GoodsInCart.getInstance();

   goodsincart.setGoods(goods);

   System.out.print("请输入要添加的商品数量：");

   int num = input.nextInt();

   if(num < 0 || num == 0) {

   System.out.println("数量要大于0 哦！");

   }

   goodsincart.setNum(num);   

   map.put(goodsId, goodsincart);    

   this.setShoppingCart(map);

   System.out.println("添加到购物车成功！");

   return;

   }else {

   if(shoppingcart.getShoppingCart().containsKey(goodsid)) {//如果购物车中已经存在该商品

   //就只修改数量

   int a = shoppingcart.getShoppingCart().get(goodsid).getNum();

   System.out.print("请输入要添加的商品数量：");

   int num = input.nextInt();

   shoppingcart.getShoppingCart().get(goodsid).setNum(a + num);

   System.out.println("添加到购物车成功！");

   return;

     }

   GoodsInCart goodsincart = GoodsInCart.getInstance();

   goodsincart.setGoods(goods);

   System.out.print("请输入要添加的商品数量：");

   int num = input.nextInt();

   if(num < 0 || num == 0) {

   System.out.println("数量要大于0 哦！");

   }

   goodsincart.setNum(num);   

   //map.put(goodsId, goodsincart);    

   shoppingcart.getShoppingCart().put(goodsid, goodsincart);

   System.out.println("添加到购物车成功！");

   return;

   }

}

}

   System.out.println("该商品还没在库中哦！");

   }

   }catch(NullPointerException e) {

    System.out.println("商品未导入！"); 

   }

  }

   //修改购物车中的商品数量

   public void updateNumInCart() {

   System.out.print("请选择要修改的商品编号：");

   Scanner input = new Scanner(System.in);

   String goodsId = input.next();

   HashMap<String,GoodsInCart> map = this.getShoppingCart();

   //System.out.println(map.size());

   if(map.containsKey(goodsId)) {

   System.out.print("请输入要修改的数量：");

   int num = input.nextInt();

   try {

          map.get(goodsId).setNum(num); 

   }catch(NullPointerException e) {

   System.out.println("购物车中还没有商品哦！");

   }

   System.out.println("数量修改成功");

   }else {

       System.out.println("亲，购物车中没有该商品，无法修改哦！");

   }

   }

   //显示购物车中的所有商品：

   public void displayAllInCart() {

   System.out.println("亲，这里是你的购物车哟！");

   HashMap<String,GoodsInCart> map = this.getShoppingCart();

   try{ 

   Set<Entry<String,GoodsInCart>> set = map.entrySet();

   //System.out.println(set.size());

   for (Entry<String, GoodsInCart> entry : set) {

   System.out.println(entry.getValue().toString());

   }

   }catch(NullPointerException e) {

    System.out.println("购物车中暂时还没有商品哦");

   }

   }

  // 结算：

   public void settleAccounts() {

   System.out.print("购物车结算清单为：");

   HashMap<String,GoodsInCart> map = this.getShoppingCart();

   Set<Entry<String,GoodsInCart>> set = map.entrySet();

   double  totalPrice = 0;

   for (Entry<String, GoodsInCart> entry : set) {

    totalPrice = totalPrice + (entry.getValue().getGoods().getPrice())*(entry.getValue().getNum());

}

   System.out.println(totalPrice);

   }

}

package com.imooc;

import java.util.HashSet;

import java.util.Iterator;

import java.util.Set;

/**

 * 商品管理类（GoodsManage）

      属性：存放商品的容器（goodsSet）：Set类型

      方法：

      －构造方法

      －getter和setter方法

      －商品信息导入：public void importGoods();

      －显示所有商品信息：public void displayAllGoods();

 * @author Willer   He

 *

 */

public class GoodsManage {

      private HashSet<Goods> goodsSet;

      //构造方法

      private GoodsManage() {

      }

private GoodsManage(HashSet<Goods> goodsSet) {

super();

this.goodsSet = goodsSet;

}

//创建对象

static GoodsManage goodsmanage = null;

public static GoodsManage getInstance() {

if(goodsmanage == null) {

goodsmanage = new GoodsManage();

return  goodsmanage;

}

return  goodsmanage;

}

public HashSet<Goods> getGoodsSet() {

return goodsSet;

}

public void setGoodsSet(HashSet<Goods> goodsSet) {

this.goodsSet = goodsSet;

}

//商品信息导入

public void importGoods() {

Goods g1 = new Goods("014527as","木马人鼠标",99,"木马人，为游戏而生");

Goods g2 = new Goods("017827as","AOC显示器",1000,"视野决定价值，AOC给你更广的视野空间");

Goods g3 = new Goods("016727as","七匹狼夹克",499,"专注品质男装");

Goods g4 = new Goods("014727as","微星笔记本",6000,"发烧级游戏本，畅玩网游");

Goods g5 = new Goods("012427as","三星固态硬盘120G",599,"每一次迈步，只为想更快的你");

Goods g6 = new Goods("014586as","安踏篮球鞋",399,"防滑，更防护你");

Goods g7 = new Goods("014587as","Huawei/华为P20 Pro",4488,"莱卡双摄");

Goods g8 = new Goods("017837as","华为honor/荣耀 荣耀10",2599,"2400万AI摄影 2400万AI摄影，智能识别500多种场景");

Goods g9 = new Goods("075327as","影驰GTX1060 GAMER 6G",2139,"大吉大利，晚上吃鸡");

Goods g10 = new Goods("078427as","Apple/苹果 Ipad 2017款",2158,"方寸间，乐趣全开");

HashSet<Goods> goodsSet =  new HashSet<Goods>();    

    goodsSet.add(g1);

    goodsSet.add(g2);

    goodsSet.add(g3);

    goodsSet.add(g4);

    goodsSet.add(g5);     

    goodsSet.add(g6);

    goodsSet.add(g7);

    goodsSet.add(g8);

    goodsSet.add(g9);

    goodsSet.add(g10);

    this.setGoodsSet(goodsSet);

    System.out.println("商品导入成功！");

}

//显示所有商品信息：

public void displayAllGoods() {

try {

Set<Goods> set = this.getGoodsSet();

if(set.size() == 1) {

System.out.println("商品列表为空，请先导入");

}else {

Iterator<Goods> it = set.iterator();

while(it.hasNext()) {

    System.out.println(it.next().toString());

}

}

}catch (NullPointerException e){

     System.out.println("商品列表为空，请先导入");

}

}

}

package com.imooc;

//商品类

public class Goods {

     private String  goodsId;//商品编号

     private String  goodsName;//商品名称

     private double  price;//商品价格

     private String  goodsDesp;//商品描述

     //构造方法

     public Goods() {

     }

public Goods(String goodsId, String goodsName, double price, String goodsDesp) {

super();

this.goodsId = goodsId;

this.goodsName = goodsName;

this.price = price;

this.goodsDesp = goodsDesp;

}

public String getGoodsId() {

return goodsId;

}

public void setGoodsId(String goodsId) {

this.goodsId = goodsId;

}

public String getGoodsName() {

return goodsName;

}

public void setGoodsName(String goodsName) {

this.goodsName = goodsName;

}

public double getPrice() {

return price;

}

public void setPrice(double price) {

this.price = price;

}

public String getGoodsDesp() {

return goodsDesp;

}

public void setGoodsDesp(String goodsDesp) {

this.goodsDesp = goodsDesp;

}

@Override

public int hashCode() {

final int prime = 31;

int result = 1;

result = prime * result + ((goodsDesp == null) ? 0 : goodsDesp.hashCode());

result = prime * result + ((goodsId == null) ? 0 : goodsId.hashCode());

result = prime * result + ((goodsName == null) ? 0 : goodsName.hashCode());

long temp;

temp = Double.doubleToLongBits(price);

result = prime * result + (int) (temp ^ (temp >>> 32));

return result;

}

@Override

public boolean equals(Object obj) {

if( this.equals(obj)) {

return true;

}

if( obj.getClass() == Goods.class) {

   Goods goods = (Goods)obj;

   return goods.goodsId == goodsId;

}

return false;

}

@Override

public String toString() {

return "商品 [goodsId=" + goodsId + ", 商品名字=" + goodsName + ", 商品价格=" + price + ", 商品描述="

+ goodsDesp + "]";

}

}

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