添加商品到购物车报错

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package com.imooc.goods;
/**
 * 商品信息类
 * @author ZYH
 *
 */
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) {
        this.setGoodsId(goodsId);
        this.setGoodsName(goodsName);
        this.setPrice(price);
        this.setGoodsDesp(goodsDesp);
    }
 
    // get、set方法
    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 == obj)
            return true;
        if (obj.getClass() == Goods.class) {
            Goods goods = (Goods) obj;
            return goods.getGoodsId().equals(goodsId) && goods.getGoodsName().equals(goodsName)
                    && (goods.getPrice() == price) && goods.getGoodsDesp().equals(goodsDesp);
        }
        return false;
    }
 
    @Override
    public String toString() {
        return "商品信息[编号：" + this.getGoodsId() + ", 名称：" + this.getGoodsName() + ", 价格：" + this.getPrice() + ", 描述："
                + this.getGoodsDesp() + "]";
    }
 
}
 
package com.imooc.goods;
/**
 * 商品管理类
 */
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
 
public class GoodsManage {
    private Set<Goods> goods;//存放集合
 
    public Set<Goods> getGoods() {
        return goods;
    }
 
    public void setGoods(Set<Goods> goods) {
        this.goods = goods;
    }
     
    //构造方法
    public GoodsManage() {
         
    }
     
    public GoodsManage(Set<Goods> goods) {
        this.setGoods(goods);
    }
     
    Set<Goods> set=new HashSet<Goods>();
     
    //商品信息导入
    public void importGoods() {
        Goods good1=new Goods("goods001","水杯",56,"不锈钢水杯");
        Goods good2 = new Goods("goods002", "饮水机", 299, "带净化功能的饮水机");
        Goods good3 = new Goods("goods003", "笔记本电脑", 4999, "15寸笔记本电脑");
        Goods good4 = new Goods("goods004", "手机", 2300, "android手机");
        set.add(good1);
        set.add(good2);
        set.add(good3);
        set.add(good4);
        System.out.println("商品信息导入成功 ！");
         
    }
     
    //显示所有商品信息
    public void displayAllGoods() {
        if(set.size()==0) {
            System.out.println("商品为空，请导入");
        }else {
            Iterator<Goods> it=set.iterator();
            while(it.hasNext()) {
                System.out.println(it.next());
            }
        }
    }
 
}
 
package com.imooc.goods;
/**
 * 购物车中的商品信息类
 * @author ZYH
 *
 */
public class GoodsInCart {
    private Goods goods;//商品信息
    private int num;//商品数量
     
    //构造方法
    public GoodsInCart() {
         
    }
    public GoodsInCart(Goods goods,int num) {
        this.setGoods(goods);
        this.setNum(num);
    }
 
    public Goods getGoods() {
        return goods;
    }
 
    public void setGoods(Goods goods) {
        this.goods = goods;
    }
 
    public int getNum() {
        return num;
    }
 
    public void setNum(int num) {
        this.num = num;
    }
     
 
}
 
package com.imooc.goods;
 
import java.util.HashMap;
import java.util.Iterator;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Scanner;
import java.util.Set;
 
/**
 * 购物车类
 * 
 * @author ZYH
 *
 */
public class ShoppingCart {
    private Map<String, GoodsInCart> shoppingCart;// Map类购物车
 
    // 构造方法
    public ShoppingCart() {
 
    }
 
    public ShoppingCart(Map<String, GoodsInCart> shoppingCart) {
        this.setShoppingCart(shoppingCart);
    }
 
    public Map<String, GoodsInCart> getShoppingCart() {
        return shoppingCart;
    }
 
    public void setShoppingCart(Map<String, GoodsInCart> shoppingCart) {
        this.shoppingCart = shoppingCart;
    }
 
    Map<String, GoodsInCart> shopping = new HashMap<String, GoodsInCart>();
    Scanner sc = new Scanner(System.in);
 
    /**
     * 添加商品到购物车
     * 
     * @param gm
     */
    public void addGoodsToCart(GoodsManage gm) {
        Set<Goods> set = gm.getGoods();
        boolean flag;
        Goods goods;
        String str;
        if (gm.getGoods().size()==0) {
            System.out.println("购物车为空！");
        } else {
            gm.displayAllGoods();
            for (Goods a : set) {
                System.out.println("请输入购买的商品编码：");
                str =sc.next();
                if (a.getGoodsId().equals(str)) {
                    flag = true;
                    goods = a;
                    break;
                }
                if (flag = true) {
                    System.out.println("请输入购买数量：");
                    int n = sc.nextInt();
                    GoodsInCart go = new GoodsInCart(a, n);
                    shopping.put(str, go);
                } else {
                    System.out.println("没找到该商品！");
                }
 
            }
        }
 
    }
 
    /**
     * 修改购物车中的商品数量
     */
    public void updateNumInCart() {
        Set<String> set = shopping.keySet();
        String s = null;
        int n = 0;
        for (String str : set) {
            System.out.println("请输入要修改的商品编号：");
            s = sc.next();
            if (str.equals(s)) {
                System.out.println("请输入要修改的数量：");
                n = sc.nextInt();
                if (n == 0) {
                    set.remove(str);
                    System.out.println("因为数量为0，故已移除该商品");
                }
                shopping.get(str).setNum(n);
            }
            Set<Entry<String, GoodsInCart>> set1 = shopping.entrySet();
            for (Entry<String, GoodsInCart> entry : set1) {
                System.out.println(entry.getValue());
            }
        }
    }
 
    /**
     * 显示购物车中所有商品
     */
    public void displayAllInCart() {
        Set<Entry<String, GoodsInCart>> set = shopping.entrySet();
        if(set.size()==0) {
            System.out.println("购物车空，请补充商品");
        }
        for (Entry<String, GoodsInCart> entry : set) {
            System.out.println(entry.getValue());
        }
    }
 
    /**
     * 结算
     */
    public void settleAccounts() {
        Set<Entry<String, GoodsInCart>> set = shopping.entrySet();
        int sum = 0;
        for (Entry<String, GoodsInCart> s : set) {
            sum += (s.getValue().getGoods().getPrice() * s.getValue().getNum());
        }
        System.out.println("总金额为：" + sum);
        set.clear();//清空购物车
    }
 
}
 
package com.imooc.goods;
/**
 * 测试类
 */
import java.util.Scanner;
import java.util.Set;
 
public class TestDemo {
 
    public static void main(String[] args) {
        GoodsManage gm = new GoodsManage();
        ShoppingCart SC = new ShoppingCart();
        Scanner sc = new Scanner(System.in);
        boolean flag = true;
        int n = 0;
        while (flag) {
            System.out.println("*********************************");
            System.out.println("          主菜单           ");
            System.out.println("     1-商品管理        ");
            System.out.println("     2-购物车            ");
            System.out.println("     0-退出                ");
            System.out.println("*********************************");
            n = sc.nextInt();
            flag = flag;
            if (n < 0 || n > 2) {
                System.out.println("输入错误，请重新输入！");
                flag = true;
                continue;
            }else if(n==0) {
                System.out.println("***欢迎您下次光临***");
                break;
            }else {
                switch (n) {
                case 1:
                    while (true) {
                        System.out.println("*********************************");
                        System.out.println("           商品管理");
                        System.out.println("     1-商品信息导入      ");
                        System.out.println("     2-显示所有商品信息  ");
                        System.out.println("     9-返回上一级菜单      ");
                        System.out.println("*********************************");
                        int i = sc.nextInt();
                        if (i != 1 && i != 2 && i != 9) {
                            System.out.println("输入不正确，请重新输入！");
                            continue;
                        } else {
                            switch (i) {
                            case 1:
                                gm.importGoods();
                                break;
                            case 2:
                                gm.displayAllGoods();
                                break;
                            }
                        }
                        if (i == 9) {
                            flag = true;
                            break;
                        }
 
                    }
                    break;
                case 2:
                    while (true) {
                        System.out.println("*********************************");
                        System.out.println("            购物车管理");
                        System.out.println("      1-添加商品到购物车");
                        System.out.println("      2-修改购物车中的商品数量");
                        System.out.println("      3-显示购物车中的所有商品信息");
                        System.out.println("      4-结算");
                        System.out.println("      9-返回上一级菜单");
                        System.out.println("*********************************");
                        int i = sc.nextInt();
                        if (i < 1 || i > 4 && i!= 9) {
                            System.out.println("输入不正确，请重新输入！");
                            continue;
                        }else {
                            switch (i) {
                            case 1:
                                SC.addGoodsToCart(gm);
                                break;
                            case 2:
                                SC.updateNumInCart();
                                break;
                            case 3:
                                SC.displayAllInCart();
                                break;
                            case 4:
                                SC.settleAccounts();
                                break;
                            }
                        }
                        if (i == 9) {
                            flag = true;
                            break;
                        }
                    }break;
                 
                }
            }
        }
 
    }
 
}

爱迷糊的坏人 2018-01-24

源自：Java集合 5-1 购物车需求

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2回答

THappy 回答被采纳获得+3积分 2018-01-25 11:31:07

你好，在GoodsManage类中定义了一个private Set<Goods> goods;属性集合，又定义了一个Set<Goods> set=new HashSet<Goods>();集合属性，这两个保留一个就可以了，建议如果保留前者，要写成private Set<Goods> goods=new HashSet<Goods>();来初始化集合。祝学习愉快~

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爱迷糊的坏人提问者 #1

非常感谢！

2018-01-25 12:57:05
爱迷糊的坏人提问者 #2

public void addGoodsToCart(GoodsManage gm) { if (gm.getGoods().size() == 0) { System.out.println("购物车为空！"); System.out.println("按任意键返回上一级"); } else { gm.displayAllGoods(); System.out.println("请输入购买的商品编码："); String str = sc.next(); Iterator<Goods> it=gm.getGoods().iterator(); while(it.hasNext()) { if(str.equals(it.next().getGoodsId())) { System.out.println("请输入要添加的数量"); int num=sc.nextInt(); GoodsInCart goodsInCart=new GoodsInCart(it.next(),num); shopping.put(str, goodsInCart); break; }else { System.out.println("该编号不存在"); break; } } } 修改后，可判断为空，但还是无法识别商品编号

2018-01-25 13:39:58
THappy 回复提问者爱迷糊的坏人 #3

1、在addGoodsToCart（）方法的while循环中，第一次循环判断输入的str与当前遍历的商品的id不相等时if判断不成立，于是执行else中的代码，输出该编号不存在，接着break跳出循环，就不再继续循环查找了。所以，可以参考如下思路： 1）在while循环前定义一个布尔型变量flag:boolean flag=true; 2）while(it.hasNext()){ Goods g=it.next(); }

2018-01-25 16:46:53

点开查看后面4条评论

THappy 2018-01-26 15:51:22

我这里把你的代码修改后可以正常添加商品到购物车了，下面是修改后的代码和正常添加商品的运行截图，为了方便查看效果，展示购物车中的商品的方法也稍作了修改，建议再仔细对照参考一下~

public void addGoodsToCart(GoodsManage gm) {
        if (gm.getGoods().size() == 0) {
            System.out.println("未导入商品！");
        } else {
            gm.displayAllGoods();
            Iterator<Goods> it = gm.getGoods().iterator();
            System.out.println("请输入购买的商品编码：");
            String str = sc.next();
            boolean flag = true;
            while (it.hasNext()) {
                Goods g = it.next();
                if (str.equals(g.getGoodsId())) {
                    flag=true;
                    System.out.println("请输入要添加的数量");
                    int num = sc.nextInt();
                    GoodsInCart goodsInCart = new GoodsInCart(g, num);
                    shopping.put(str, goodsInCart);
                    break;
                } else {
                    flag = false;
                }
                 
            }
            if (!flag) {
                System.out.println("商品编号不存在");
                 
            }
        }
    }
    public void displayAllInCart() {
        Set<Entry<String, GoodsInCart>> set = shopping.entrySet();
        if (set.size() == 0) {
            System.out.println("购物车空，请补充商品");
        }
        for (Entry<String, GoodsInCart> entry : set) {//此处做了修改，因为需要展示购物车中的每个商品信息
            GoodsInCart gic = entry.getValue();
            System.out.println(gic.getGoods()+"数量："+gic.getNum());
        }
    }