Java 基础语法

Posted 2022-10-22 zach0812

 

使用ide来进行编程!

 

对于java来说，最好的idle 是intellijidea(IDEA)

通过一个例子练习　idea !

 

一：超市管理系统功能

 

使用ide来进行编程，java最好的ide 是idea

 

 

 

  1 import java.util.ArrayList;
  2 import java.util.Scanner;
  3 
  4 public class Shop 
  5     public static void main(String[] args) 
  6         ArrayList<Fruit> array = new ArrayList<Fruit>();
  7         init(array);
  8         while (true) 
  9             mainMenu();
 10             int choose = chooseFunc();
 11             switch (choose) 
 12                 case 1:
 13                     //货物清单
 14                     showFruit(array);
 15                     break;
 16                 case 2:
 17                     //添加货物
 18                     addItem(array);
 19                     break;
 20                 case 3:
 21                     //删除货物
 22                     delItem(array);
 23                     break;
 24                 case 4:
 25                     //修改货物
 26                     modifyItem(array);
 27                     break;
 28                 case 5:
 29                     //退出
 30                     return;
 31 
 32             
 33 
 34         
 35     
 36 
 37     //初始化列表
 38     public static void init(ArrayList<Fruit> arr) 
 39         //创建多个Fruit 类型，并且为属性赋值
 40         Fruit f1 = new Fruit();
 41         f1.ID = 111111;
 42         f1.name = "苹果";
 43         f1.price = 12;
 44 
 45         Fruit f2 = new Fruit();
 46         f2.ID = 22222;
 47         f2.name = "句子";
 48         f2.price = 31;
 49 
 50         Fruit f3 = new Fruit();
 51         f3.ID = 333333;
 52         f3.name = "香蕉";
 53         f3.price = 42;
 54 
 55         arr.add(f1);
 56         arr.add(f2);
 57         arr.add(f3);
 58     
 59 
 60     //提示用户做选择，让选择序号
 61     public static void mainMenu() 
 62         System.out.println();
 63         System.out.println("=======欢迎光临超市=========");
 64         System.out.println("1:货物清单 2：添加货物 3：删除货物 4：修改货物 5：退出");
 65         System.out.println("请你输入要操作的功能序号>>>");
 66     
 67 
 68     //接收用户的键盘输入
 69     public static int chooseFunc() 
 70         Scanner scan = new Scanner(System.in);
 71         int num = scan.nextInt();
 72         return num;
 73     
 74 
 75     public static void showFruit(ArrayList<Fruit> arr) 
 76         System.out.println();
 77         System.out.println("========商品库存清单=========");
 78         System.out.println("商品编号      商品名称     商品单价");
 79 
 80         for (int i = 0; i < arr.size(); i++) 
 81             Fruit item = arr.get(i);
 82             System.out.println(item.ID + " " + item.name + " " + item.price);
 83         
 84 
 85     
 86 
 87     public static void addItem(ArrayList<Fruit> arr) 
 88         Scanner scan = new Scanner(System.in);
 89         System.out.println("请输入商品的编号");
 90         int ID = scan.nextInt();
 91 
 92         System.out.println("请输入商品的名字");
 93         String name = scan.next();
 94 
 95         //商品单价
 96         System.out.println("请输入商品单价");
 97         double price = scan.nextDouble();
 98 
 99         Fruit item = new Fruit();
100         item.ID = ID;
101         item.name = name;
102         item.price = price;
103 
104         arr.add(item);
105     
106 
107     public static void delItem(ArrayList<Fruit> arr) 
108         System.out.println("请输入要删除的商品编号");
109 
110         Scanner scan = new Scanner(System.in);
111         int id = scan.nextInt();
112 
113         for (int i = 0; i < arr.size(); i++) 
114             if (arr.get(i).ID == id) 
115                 arr.remove(i);
116                 System.out.println("删除成功！ ");
117                 return;  //此处不用break　　因为最后一句话
118             
119         
120         System.out.println("您输入的ｉd 不存在");
121     
122     public static void modifyItem(ArrayList<Fruit> arr )
123         System.out.println("请输入要删除的商品ＩＤ");
124 
125         Scanner scan  = new Scanner(System.in);
126         int id = scan.nextInt();
127 
128         for (int i = 0; i <arr.size() ; i++) 
129            if(arr.get(i).ID == id)
130                Fruit item =  arr.get(i);
131                System.out.println("请输入新的商品名字");
132                item.name = scan.next();
133 
134                System.out.println("请输入新的商品价格");
135                item.price = scan.nextInt();
136            
137         
138 
139     
140 
141