Java 基础语法

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

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

public class Shop {
    public static void main(String[] args) {
        ArrayList<Fruit> array = new ArrayList<Fruit>();
        init(array);
        while (true) {
            mainMenu();
            int choose = chooseFunc();
            switch (choose) {
                case 1:
                    //货物清单
                    showFruit(array);
                    break;
                case 2:
                    //添加货物
                    addItem(array);
                    break;
                case 3:
                    //删除货物
                    delItem(array);
                    break;
                case 4:
                    //修改货物
                    modifyItem(array);
                    break;
                case 5:
                    //退出
                    return;

            }

        }
    }

    //初始化列表
    public static void init(ArrayList<Fruit> arr) {
        //创建多个Fruit 类型，并且为属性赋值
        Fruit f1 = new Fruit();
        f1.ID = 111111;
        f1.name = "苹果";
        f1.price = 12;

        Fruit f2 = new Fruit();
        f2.ID = 22222;
        f2.name = "句子";
        f2.price = 31;

        Fruit f3 = new Fruit();
        f3.ID = 333333;
        f3.name = "香蕉";
        f3.price = 42;

        arr.add(f1);
        arr.add(f2);
        arr.add(f3);
    }

    //提示用户做选择，让选择序号
    public static void mainMenu() {
        System.out.println();
        System.out.println("=======欢迎光临超市=========");
        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");
        System.out.println("请你输入要操作的功能序号>>>");
    }

    //接收用户的键盘输入
    public static int chooseFunc() {
        Scanner scan = new Scanner(System.in);
        int num = scan.nextInt();
        return num;
    }

    public static void showFruit(ArrayList<Fruit> arr) {
        System.out.println();
        System.out.println("========商品库存清单=========");
        System.out.println("商品编号      商品名称     商品单价");

        for (int i = 0; i < arr.size(); i++) {
            Fruit item = arr.get(i);
            System.out.println(item.ID + " " + item.name + " " + item.price);
        }

    }

    public static void addItem(ArrayList<Fruit> arr) {
        Scanner scan = new Scanner(System.in);
        System.out.println("请输入商品的编号");
        int ID = scan.nextInt();

        System.out.println("请输入商品的名字");
        String name = scan.next();

        //商品单价
        System.out.println("请输入商品单价");
        double price = scan.nextDouble();

        Fruit item = new Fruit();
        item.ID = ID;
        item.name = name;
        item.price = price;

        arr.add(item);
    }

    public static void delItem(ArrayList<Fruit> arr) {
        System.out.println("请输入要删除的商品编号");

        Scanner scan = new Scanner(System.in);
        int id = scan.nextInt();

        for (int i = 0; i < arr.size(); i++) {
            if (arr.get(i).ID == id) {
                arr.remove(i);
                System.out.println("删除成功！ ");
                return;  //此处不用break　　因为最后一句话
            }
        }
        System.out.println("您输入的ｉd 不存在");
    }
    public static void modifyItem(ArrayList<Fruit> arr ){
        System.out.println("请输入要删除的商品ＩＤ");

        Scanner scan  = new Scanner(System.in);
        int id = scan.nextInt();

        for (int i = 0; i <arr.size() ; i++) {
           if(arr.get(i).ID == id){
               Fruit item =  arr.get(i);
               System.out.println("请输入新的商品名字");
               item.name = scan.next();

               System.out.println("请输入新的商品价格");
               item.price = scan.nextInt();
           }
        }

    }

}