public class Fruit {  //定義ID  private String id;  //定義名稱  private String name;  //定義價格  private int price;  //定義單位  private String unit;   //定義數量  private int number;  public Fruit(String id, String name, int price, String unit) {  super();  this.id = id;  this.name = name;  this.price = price;  this.unit = unit;  }  public Fruit() {  super();  // TODO Auto-generated constructor stub  }  public String getId() {  return id;  }  public void setId(String id) {  this.id = id;  }  public String getName() {  return name;  }  public void setName(String name) {  this.name = name;  }  public int getPrice() {  return price;  }  public void setPrice(int price) {  this.price = price;  }  public String getUnit() {  return unit;  }  public void setUnit(String unit) {  this.unit = unit;  }  public int getNumber() {  return number;  }  public void setNumber(int number) {  this.number = number;  }   //獲取價格  public int getMoney(){  return price * number;  }  } 

import java.io.IOException; import java.util.Scanner;  public class FruitTest {  public static void main(String[] args) throws IOException {  Scanner sc = new Scanner(System.in);  Shopper shopper = new Shopper();  Manager manager = new Manager();    while(true){   System.out.println( "    歡迎光臨水果系統");   System.out.println("請輸入你的角色:(1.顧客 2.管理員 3.退出)");   int choice = sc.nextInt();   switch(choice){   case 1:   //顧客   shopper.shop();   break;   case 2:   //管理員   manager.manager();   break;   case 3:   System.exit(0);   default:   System.out.println("你的輸入有誤!");   }  }    } } 

import java.io.BufferedReader; import java.io.FileReader; import java.io.IOException; import java.util.ArrayList; import java.util.Scanner;  public class Shopper {  public void shop() throws IOException {  Scanner sc = new Scanner(System.in);  ArrayList<Fruit> list = new ArrayList<Fruit>();  check(list);  while (true) {   System.out    .println("     歡迎光臨水果系統");   System.out    .println("請輸入你的操作:(1.查看水果 2.購買水果 3.結賬  4.退出)");   int choice = sc.nextInt();   switch (choice) {   case 1:   // 查看水果   print(list);   break;   case 2:   // 購買水果   buy(list);   break;   case 3:   // 結賬   checkOut(list);   break;   case 4:   // 退出   return;   default:   System.out.println("你輸入的操作有誤!");   }   }   }   //結賬  private void checkOut(ArrayList<Fruit> list) {  int sum = 0;  for (int i = 0; i < list.size(); i++) {   Fruit f = list.get(i);   sum += f.getMoney();  }    if(sum>200){   int newSum = (int) (sum * 0.9);   System.out.println("金額：" + sum+ "元, 優惠價格："+ newSum+"元");  }else{   System.out.println("金額：" + sum+"元");  }    //結完賬后，將數量清0  for (int i = 0; i < list.size(); i++) {   Fruit f = list.get(i);   f.setNumber(0);  }  }   // 購買水果  public void buy(ArrayList<Fruit> list) throws IOException {  Scanner sc1 = new Scanner(System.in);  Scanner sc2 = new Scanner(System.in);  print(list);  while (true) {   System.out.println("購買超過200元，享受九折優惠！");   System.out.println("請輸入想要購買的水果的ID：(如果不想購買，請輸入-1退出)");   String id = sc1.nextLine();   if ("-1".equals(id)) {   System.out.println("購買已結束，請去結賬 ");   return;   } else {   boolean flag = false;   for (int i = 0; i < list.size(); i++) {    Fruit f = list.get(i);    if(f.getId().equals(id)) {    System.out.println("請輸入購買" + f.getName() + "數量： ");    int num = sc2.nextInt();    f.setNumber(num);    flag = true;    }   }   if(!flag){    System.out.println("你輸入的水果ID不正確,請重新輸入");   }   }   }   }   // 查看水果  public void check(ArrayList<Fruit> list) throws IOException {  BufferedReader br = new BufferedReader(new FileReader("fruit.txt"));  String line;  while ((line = br.readLine()) != null) {   String[] str = line.split(" ");   Fruit f = new Fruit(str[0], str[1], Integer.parseInt(str[2]),    str[3]);   list.add(f);  }  br.close();  }   public void print(ArrayList<Fruit> list) {  System.out.println("ID/t水果/t價格/t單位");  for (int i = 0; i < list.size(); i++) {   Fruit f = list.get(i);   System.out.println(f.getId() + "/t" + f.getName() + "/t"    + f.getPrice() + "/t" + f.getUnit());  }  } } 

import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.FileNotFoundException; import java.io.FileReader; import java.io.FileWriter; import java.io.IOException; import java.util.ArrayList; import java.util.Scanner;  public class Manager {   public void manager() throws IOException {  if (load()) {    Scanner sc = new Scanner(System.in);   while (true) {   ArrayList<Fruit> list = new ArrayList<Fruit>();   check(list);   System.out    .println("請輸入您的操作： (1.查看水果種類  2.增加水果種類 3.修改水果種類 4.刪除水果種類  5退出)");   int choice = sc.nextInt();   switch (choice) {   case 1:    // 查看水果種類    print(list);    break;   case 2:    // 增加水果種類    addFruit(list);    break;   case 3:    // 修改水果種類    reverse(list);    break;   case 4:    // 刪除水果種類    remove(list);    break;   case 5:    // 退出    return;   default:    System.out.println("你輸入的操作有誤!");    break;   }   }   } else {   return;  }  }   public void remove(ArrayList<Fruit> list) throws IOException {  Scanner sc = new Scanner(System.in);  print(list);  System.out.println("請輸入要刪除的水果ID: ");  String id = sc.nextLine();  for (int i = 0; i < list.size(); i++) {   Fruit f = list.get(i);   if(f.getId().equals(id)){   list.remove(i);   write(list);   System.out.println("刪除成功");   return;   }  }  System.out.println("找不到要刪除的水果ID!");  }   //修改水果  public void reverse(ArrayList<Fruit> list) throws IOException {  Scanner sc1 = new Scanner(System.in);  Scanner sc2 = new Scanner(System.in);  print(list);  System.out.println("請輸入要修改的水果ID: ");  String id = sc1.nextLine();  for (int i = 0; i < list.size(); i++) {   Fruit f = list.get(i);   if(f.getId().equals(id)){   System.out.println("請輸入水果的名稱: ");   String name = sc1.nextLine();   System.out.println("請輸入水果的價格: ");   int price = sc2.nextInt();   System.out.println("請輸入水果的單位: ");   String unit = sc1.nextLine();      f.setName(name);   f.setPrice(price);   f.setUnit(unit);      write(list);   System.out.println("修改成功");   return;   }  }  System.out.println("找不到要修改的水果ID!");      }   //增加水果  public void addFruit(ArrayList<Fruit> list) throws IOException {  Scanner sc1 = new Scanner(System.in);  Scanner sc2 = new Scanner(System.in);  print(list);  System.out.println("請輸入要增加水果的ID: ");  String id = sc1.nextLine();  for (int i = 0; i < list.size(); i++) {   Fruit f = list.get(i);   if(f.getId().equals(id)){   System.out.println("水果ID名重復!");   return;   }  }  System.out.println("請輸入水果的名字: ");  String name = sc1.nextLine();  System.out.println("請輸入水果的價格: ");  int price = sc2.nextInt();  System.out.println("請輸入水果的單位: ");  String unit = sc1.nextLine();    Fruit f = new Fruit(id, name, price, unit);  list.add(f);    write(list);  System.out.println("增加成功");    }  //寫入新加的種類  private void write(ArrayList<Fruit> list) throws IOException {  BufferedWriter bw = new BufferedWriter(new FileWriter("fruit.txt"));  for (int i = 0; i < list.size(); i++) {   Fruit f = list.get(i);   bw.write(f.getId()+" " + f.getName() + " " + f.getPrice() + " " + f.getUnit());   bw.newLine();  }  bw.close();  }    public void print(ArrayList<Fruit> list) {  System.out.println("ID/t水果/t價格/t單位");  for (int i = 0; i < list.size(); i++) {   Fruit f = list.get(i);   System.out.println(f.getId() + "/t" + f.getName() + "/t"    + f.getPrice() + "/t" + f.getUnit());  }  }   // 查看水果  public void check(ArrayList<Fruit> list) throws IOException {  BufferedReader br = new BufferedReader(new FileReader("fruit.txt"));  String line;  while ((line = br.readLine()) != null) {   String[] str = line.split(" ");   Fruit f = new Fruit(str[0], str[1], Integer.parseInt(str[2]),    str[3]);   list.add(f);  }  br.close();  }   // 登陸系統  public boolean load() throws FileNotFoundException, IOException {  Scanner sc = new Scanner(System.in);   System.out.println("請輸入用戶名： ");  String username = sc.nextLine();  System.out.println("請輸入密碼： ");  String password = sc.nextLine();  BufferedReader br = new BufferedReader(new FileReader("admin.txt"));  String line = br.readLine();  String[] str = line.split(",");  if (str[0].equals(username) && str[1].equals(password)) {   System.out.println("歡迎您進入水果管理系統： " + username);   return true;  } else {   System.out.println("你的用戶名或密碼輸入不正確，無法進入管理系統");   return false;  }  } }