完成了商城项目，需要好好消化一下

import com.team1.util.ScannerUtil;import java.sql.SQLOutput;
import java.util.Scanner;public class HomePage {public static void main(String[] args) throws Exception {HomePage homePage = new HomePage();homePage.loginView();homePage.homeView();}public void homeView() {System.out.println("欢迎登录商城，请选择业务：");boolean flag = true;System.out.println("1.购买商品 2.查看个人信息 3.查看购物车 4.付款 5.账户充值 6.退出商城");while (true) {String function = ScannerUtil.getInput();switch (function) {case ShopConstent.FUNCTION_SHOP:Shop shop = new Shop();shop.shopView();break;case ShopConstent.FUNCTION_PERSONAL:User user = new User();user.userView();break;case ShopConstent.FUNCTION_CART://System.out.println("购物车目前已有商品："+ ShopConstent.LOGIN_USER.getCart().getCartMessage());Cart cart = new Cart();cart.cartView();break;case ShopConstent.FUNCTION_PAYMENT:ShopConstent.LOGIN_USER.pay();break;case ShopConstent.FUNCTION_RECHARGE:Recharge recharge = new Recharge();recharge.rechargeView();break;case ShopConstent.FUNCTION_EXIT:HomePage homePage = new  HomePage();homePage.loginView();homePage.homeView();break;}}}//展示注册登录页面public void loginView(){boolean flag = true;while (flag){System.out.println("请选择功能："+ShopConstent.USER_LOGIN+"登录 "+ShopConstent.USER_REGIST+"注册");Scanner scanner = new Scanner(System.in);String function = scanner.next();//User user = new User();switch (function){case ShopConstent.USER_LOGIN:flag  = !ShopConstent.LOGIN_USER.login();break;case ShopConstent.USER_REGIST:ShopConstent.LOGIN_USER.regist();}}}
}

import com.sun.org.apache.xpath.internal.operations.Or;
import com.team1.util.ScannerUtil;import java.io.*;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;public class User {private String username;private String password;private Cart cart;public User(){this.cart = new Cart();}public void userView(){System.out.println("现在显示您的个人信息，请选择：1.修改 2.返回上层页面");System.out.println("账户："+ShopConstent.LOGIN_USER.getUsername()+"  密码："+ShopConstent.LOGIN_USER.getPassword());Scanner scanner = new Scanner(System.in);String function = scanner.next();if(function.equals("1")){ShopConstent.LOGIN_USER.regist();System.out.println("修改信息成功，请输入2返回上层页面。");}else if(function.equals("2")){HomePage homePage = new HomePage();homePage.homeView();}else{System.out.println("输入非法，请重新输入。");userView();}/*switch (function) {case "1":// User user = new User();ShopConstent.LOGIN_USER.regist();System.out.println("修改信息成功，请输入2返回上层页面。");break;case "2":HomePage homePage = new HomePage();homePage.homeView();break;default:System.out.println("输入非法，请重新输入。");userView();break;}*/}public boolean login() {System.out.println("请输入用户名：");//String username = ScannerUtil.getInput();System.out.println();System.out.println("请输入密码：");String password = ScannerUtil.getInput();//String username = ScannerUtil.getInput();User user = getUsersByName(username);if(user == null){System.out.println("用户名不存在,登录失败");return false;}//如果拿到user 去比对密码if(!password.equals(user.password)){System.out.println("密码错误,登录失败");return false;}//保存已登录的用户ShopConstent.LOGIN_USER = getUsersByName(username);System.out.println("登录成功");return true;}public boolean regist(){//System.out.println("这是注册方法");System.out.println("请输入用户名：");//String username = ScannerUtil.getInput();System.out.println();System.out.println("请输入密码：");String password = ScannerUtil.getInput();User user = new User();user.setUsername(username);user.setPassword(password);//保存用户saveUser(user);return true;}//传参传入 商品id 商品购买数量public boolean addGoodsToCart(String id,int goodsCount){//1.就应该查一下goods信息//静态方法拿类名直接调//Goods goods = Goods.getGoodsById(id);//2.把商品加入购物车cart.addGoods(id,goodsCount);return true;}//获得所有的Userprivate List<User> getUsers(String url)  {List<User> users = new ArrayList<>();//主动关闭流try(FileReader fs = new FileReader(url);BufferedReader bf = new BufferedReader(fs);) {String userStr = null;while ((userStr = bf.readLine()) != null) {//读一行封装一行String[] str = userStr.split("_");User user = new User();user.setUsername(str[0]);user.setPassword(str[1]);users.add(user);}}catch (IOException ex){ex.printStackTrace();}return users;}//获取一个user的方法public User getUsersByName(String name){getUsers(ShopConstent.USER_PATH);List<User> users = getUsers(ShopConstent.USER_PATH);for (User user : users){if(user.getUsername().equals(name)){return user;}}return  null;}public boolean saveUser(User user) {FileWriter fw = null;BufferedWriter bw =null;try{fw = new FileWriter(ShopConstent.USER_PATH,true);bw = new BufferedWriter(fw);bw.newLine();bw.append(user.getUsername()).append("_").append(user.getPassword());}catch (IOException ex){ex.printStackTrace();}finally {try {if(bw != null){bw.close();}if(fw != null){fw.close();}}catch (IOException ex){ex.printStackTrace();}}return true;}public void pay(){//拿到购物车总价List<Order> cartMessage = cart.getCartMessage();double cartTotalMoney = 0;for (Order order : cartMessage) {//把每一条信息加一起获得总价cartTotalMoney += order.getTotalMoney();}if(cartTotalMoney>ShopConstent.USER_RECHARG){System.out.println("您的余额不足，请充值");}else {ShopConstent.USER_RECHARG = ShopConstent.USER_RECHARG - cartTotalMoney;System.out.println("购买成功，您本次消费为："+cartTotalMoney+"  您的账户余额为："+ShopConstent.USER_RECHARG);cart.clear();}HomePage homePage = new HomePage();homePage.homeView();}public String getUsername() {return username;}public String getPassword() {return password;}public void setUsername(String username) {this.username = username;}public void setPassword(String password) {this.password = password;}public Cart getCart() {return cart;}public void setCart(Cart cart) {this.cart = cart;}@Overridepublic String toString() {return "User{" +"username='" + username + '\'' +", password='" + password + '\'' +", cart=" + cart +'}';}
}

import com.team1.util.ScannerUtil;import java.util.List;
import java.util.Scanner;public class Shop {/* public static void main(String[] args) throws Exception {//面向对象Shop shop = new Shop();//shop.loginView();//shop.homeView();shop.shopView();//使用静态对象//loginView();}*//* private void homeView() {System.out.println("欢迎登录商城，请选择业务：");boolean flag = true;System.out.println("1.购买商品 2.查看个人信息 3.查看购物车 4.付款 5.账户充值 6.退出商城");while (true){String function = ScannerUtil.getInput();switch (function){case ShopConstent.FUNCTION_SHOP://Shop shop = new Shop();Shop.shopView();break;case ShopConstent.SHOP_TYPE_CRUET:showGoodsMessage(ShopConstent.SHOP_TYPE_CRUET);break;case ShopConstent.SHOP_TYPE_NECESSITIES:showGoodsMessage(ShopConstent.SHOP_TYPE_NECESSITIES);break;}*///展示购物页面void shopView() {System.out.println("开始购物");boolean flag = true;System.out.println("1.食品 2.调味品 3.日用品 0.返回上层页面");while (true){String function = ScannerUtil.getInput();switch (function){case ShopConstent.SHOP_TYPE_FOOD:showGoodsMessage(ShopConstent.SHOP_TYPE_FOOD);break;case ShopConstent.SHOP_TYPE_CRUET:showGoodsMessage(ShopConstent.SHOP_TYPE_CRUET);break;case ShopConstent.SHOP_TYPE_NECESSITIES:showGoodsMessage(ShopConstent.SHOP_TYPE_NECESSITIES);break;case ShopConstent.SHOP_TYPE_EXIT:HomePage homePage = new HomePage();homePage.homeView();break;}}}//展示商品信息private void showGoodsMessage(String type){List<Goods> goodsByType = Goods.getGoodsByType(type);String str = "商品编号：商品名称 商品价格"+"\n";for (Goods goods : goodsByType) {str = str + goods.getId()+":"+goods.getName()+" "+goods.getPrice()+" \n";}System.out.println(str);//User user = new User();System.out.println("请输入购买商品id和数量：");String id = ScannerUtil.getInput();int goodsCount = Integer.parseInt(ScannerUtil.getInput());ShopConstent.LOGIN_USER.addGoodsToCart(id,goodsCount);//System.out.println("您购买了"+ShopConstent.LOGIN_USER.getCart().getCartMessage());shopView();}//展示注册登录页面/*public void loginView(){boolean flag = true;while (flag){System.out.println("请选择功能："+ShopConstent.USER_LOGIN+"登录 "+ShopConstent.USER_REGIST+"注册");Scanner scanner = new Scanner(System.in);String function = scanner.next();User user = new User();switch (function){case ShopConstent.USER_LOGIN:flag  = !user.login();break;case ShopConstent.USER_REGIST:user.regist();}}}*/
}

import com.sun.org.apache.xpath.internal.operations.Or;//商品信息 商品数量
public  class Order {private String goodsId;private String goodsName;private int goodsCount;private double goodsPrice;private double totalMoney;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 int getGoodsCount() {return this.goodsCount;}public void setGoodsCount(int goodsCount) {this.goodsCount = goodsCount;}public double getGoodsPrice() {return goodsPrice;}public void setGoodsPrice(double goodsPrice) {this.goodsPrice = goodsPrice;}public double getTotalMoney() {return totalMoney;}public void setTotalMoney(double totalMoney) {this.totalMoney = totalMoney;}@Overridepublic String toString() {return "Order{" +"goodsId='" + goodsId + '\'' +", goodsName='" + goodsName + '\'' +", goodsCount=" + goodsCount +", goodsPrice=" + goodsPrice +", totalMoney=" + totalMoney +'}';}
}

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;public class Goods {private String type;private String id;private String name;private double price;/*public  static  void main(String[] args){List<Goods> allGoods = Goods.getGoodsByType(ShopConstent.SHOP_TYPE_FOOD);for(Goods allGood : allGoods){System.out.println(allGood);}System.out.println(Goods.getGoodsById("1"));}*//* public static Goods getGoodsById(String id) {//使用流去文件夹找,返回LIST类型 遍历 根据id返回数据*//*  List<Goods> goodsList =new ArrayList<>();for (int i = 0; i < goodsList.size(); i++) {if(goodsList.get(i).getName().equals(id)){return goodsList.get(i);}}*//*Goods goods = new Goods();goods.setName("棒棒糖");goods.setPrice(3.5);goods.setType("食品");return goods;}*/public static List<Goods> getAllGoods(String path){List<Goods> goodsList = new ArrayList<>();//主动关闭流try(FileReader fs = new FileReader(path); BufferedReader bf = new BufferedReader(fs);) {String userStr = null;while ((userStr = bf.readLine()) != null) {//读一行封装一行String[] str = userStr.split("_");Goods goods = new Goods();goods.setId(str[0]);goods.setType(str[1]);goods.setName(str[2]);//Double的静态方法 将字符串转化为Doublegoods.setPrice(Double.parseDouble(str[3]));goodsList.add(goods);}}catch (IOException ex){ex.printStackTrace();}return goodsList;}//根据id找到一个商品public static Goods getGoodsById(String id){List<Goods> allGoods = getAllGoods(ShopConstent.SHOP_PATH);Goods targetGoods = null;for (Goods goods : allGoods){if(goods.getId().equals(id)){//if(goods.getType().equals(id)){targetGoods = goods;break;}}return targetGoods;}//查找方式 根据类查找public static List<Goods> getGoodsByType(String type){List<Goods> allGoods = getAllGoods(ShopConstent.SHOP_PATH);List<Goods> goodsType = new ArrayList<>();/*for (int i = 0; i < allGoods.size(); i++) {if(allGoods.get(i).getType().equals(type)){}}*/for (Goods goods : allGoods){if(goods.getType().equals(type)){goodsType.add(goods);}}return goodsType;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getId() {return id;}public void setId(String id) {this.id = id;}public double getPrice() {return price;}public void setPrice(double price) {this.price = price;}public String getType() {return type;}public void setType(String type) {this.type = type;}@Overridepublic String toString() {return "Goods{" +"type='" + type + '\'' +", id='" + id + '\'' +", name='" + name + '\'' +", price=" + price +'}';}
}

import com.team1.util.ScannerUtil;import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.List;public class Cart {public static List<Order> orderList = new ArrayList<>();public void cartView() {//List<Order> cartMessage = char.getSystem.out.println("购物车已有商品："+ShopConstent.LOGIN_USER.getCart().getCartMessage().toString());System.out.println("请输入0返回上一层");String str = ScannerUtil.getInput();if (str.equals("0")){HomePage homePage = new HomePage();homePage.homeView();}else{System.out.println("非法输入，请输入0返回上一层");cartView();}}//订单封装public void addGoods(String id,int goodsCount){Goods goods = Goods.getGoodsById(id);Order order = new Order();order.setGoodsId(goods.getId());order.setGoodsName(goods.getName());order.setGoodsCount(goodsCount);order.setGoodsPrice(goods.getPrice());order.setTotalMoney(goodsCount * goods.getPrice());orderList.add(order);System.out.println("您添加了： "+order.getGoodsCount() + "个" + order.getGoodsName() +" ,到购物车,共计 "+ order.getTotalMoney() + "元。");}//返回购物车信息public  List<Order> getCartMessage(){if(orderList.size() != 0){return orderList;}System.out.println("您还未添加商品，请先添加商品再购买");HomePage homePage = new HomePage();homePage.homeView();return null;}/* public void getOrder(){for (int i = 0; i < orderList.size(); i++) {return orderList.get(name);}}*///清除购物车public boolean clear(){orderList.clear();return true;}public static List<Order> getOrderList() {return orderList;}public static void setOrderList(List<Order> orderList) {Cart.orderList = orderList;}
}

今日总结：创建类后要初始化，不然会报错。
看教程一定要认真，不能中间落下一集，不然看的很迷糊。
基础一定要掌握牢固，关于集合，和面向对象要再认真看一遍。