ArrayList ：货物库存管理（遍历）

package com.oracle.demo01;

import java.util.ArrayList;
import java.util.Scanner;

public class Demo03 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        Goods g1 = new Goods();
        Goods g2 = new Goods();
        Goods g3 = new Goods();
        g1.gid = 9001;
        g1.name = "少林寺酥饼核桃";
        g1.price = 120;
        g2.gid = 9002;
        g2.name = "尚康杂粮牡丹饼";
        g2.price = 20;
        g3.gid = 9003;
        g3.name = "新疆原产哈密瓜";
        g3.price = 7;

        ArrayList<Goods> arr = new ArrayList<Goods>();
        arr.add(g1);
        arr.add(g2);
        arr.add(g3);
        while (true) {
            show();
            int choose = sc.nextInt();
            switch (choose) {
            case 1:
                getGoods(arr);
                break;
            case 2:
                addGoods(arr);
                break;
            case 3:
                updateGoods(arr);
                break;
            case 4:
                dropGoods(arr);
                break;
            case 5:
                return;
            default:
                System.out.println("您的输入有误，请重新输入！");
                break;
            }
        }
    }

    // 商品展示页面
    public static void show() {
        System.out.println("==================欢迎光临oracle超市==================");
        System.out.println("1.货物清单");
        System.out.println("2.添加货物");
        System.out.println("3.修改货物");
        System.out.println("4.删除货物");
        System.out.println("5.退出");
        System.out.println("请输入您要操作的功能序号：");
    }

    // 查询所有商品
    public static void getGoods(ArrayList<Goods> arr) {
        System.out.println("=======================商品清单======================");
        System.out.println("商品编号\t\t商品名称\t\t商品价格");
        for (int i = 0; i < arr.size(); i++) {
            System.out.println(arr.get(i).gid + "\t\t" + arr.get(i).name + "\t" + arr.get(i).price);
        }
    }

    // 添加商品
    public static void addGoods(ArrayList<Goods> arr) {
        System.out.println("请输入您要新增的商品编号：");
        Scanner sc = new Scanner(System.in);
        int id = sc.nextInt();
        System.out.println("请输入您要新增的商品名称：");
        String name = sc.next();
        System.out.println("请输入您要新增的商品价格：");
        double price = sc.nextDouble();
        Goods goods = new Goods();
        goods.gid = id;
        goods.name = name;
        goods.price = price;
        arr.add(goods);
    }

    // 修改商品
    public static void updateGoods(ArrayList<Goods> arr){
        System.out.println("请输入您要修改的商品编号(输入0返回主菜单)：");
        for(int i=0;i<arr.size();i++){
            System.out.println(arr.get(i).gid+" "+arr.get(i).name);
        }
        Scanner sc=new Scanner(System.in);
        int uid=0;
        aa:while (true) {
            int id=sc.nextInt();
            for(int i=0;i<arr.size();i++){
                if(arr.get(i).gid==id){
                    uid=id;
                    break aa;
                }else if(id==0){
                    return;
                }
            }
            System.out.println("请输入正确的商品编号(输入0返回主菜单)：");
        }
        
        System.out.println("请修改商品名称：");
        String name=sc.next();
        System.out.println("请修改商品价格：");
        double price=sc.nextDouble();
        //遍历，按id找gid
        for(int i=0;i<arr.size();i++){
            if(arr.get(i).gid==uid){
                arr.get(i).name=name;
                arr.get(i).price=price;
            }
        }

//第二种修改的方法
for (int i = 0; i < arr.size(); i++) {
    if (arr.get(i).gid == uid) {
        Goods goods=new Goods();
        goods.gid=uid;
        goods.name=name;
        goods.price=price;
        arr.set(i, goods);
    }
}

    }
    //删除商品
    private static void dropGoods(ArrayList<Goods> arr) {
        System.out.println("请输入您要删除的商品编号(输入0返回主菜单)：");
        for(int i=0;i<arr.size();i++){
            System.out.println(arr.get(i).gid+" "+arr.get(i).name);
        }
        Scanner sc=new Scanner(System.in);
        int uid=0;
        aa:while (true) {
            int id=sc.nextInt();
            for(int i=0;i<arr.size();i++){
                if(arr.get(i).gid==id){
                    uid=id;
                    break aa;
                }else if(id==0){
                    return;
                }
            }
            System.out.println("请输入正确的商品编号(输入0返回主菜单)：");
        }
        for(int i=0;i<arr.size();i++){
            if(arr.get(i).gid==uid){
                arr.remove(i);
            }
        }
    }
}