Java知识系统回顾整理01基础05控制流程02 switch

一、switch

switch 语句相当于 if else的另一种表达方式

 switch可以使用byte,short,int,char,String,enum

• 注: 每个表达式结束，都应该有一个break;
• 注: String在Java1.7之前是不支持的, Java从1.7开始支持switch用String的，编译后是把String转化为hash值，其实还是整数
• 注: enum是枚举类型，在枚举章节有详细讲解

   

public class HelloWorld {

    public static void main(String[] args) {

          

        //如果使用if else

        int day = 5;

        if (day==1)

            System.out.println("星期一");

                

        else if (day==2)

            System.out.println("星期二");

        else if (day==3)

            System.out.println("星期三");

        else if (day==4)

            System.out.println("星期四");

        else if (day==5)

            System.out.println("星期五");

        else if (day==6)

            System.out.println("星期六");

        else if (day==7)

            System.out.println("星期天");

        else

            System.out.println("这个是什么鬼？");

          

        //如果使用switch

        switch(day){

            case 1:

                System.out.println("星期一");

                break;

            case 2:

                System.out.println("星期二");

                break;

            case 3:

                System.out.println("星期三");

                break;

            case 4:

                System.out.println("星期四");

                break;

            case 5:

                System.out.println("星期五");

                break;

            case 6:

                System.out.println("星期六");

                break;

            case 7:

                System.out.println("星期天");

                break;

            default:

                System.out.println("这个是什么鬼？");

        }

          

    }

}

   

二、练习--季节

题目：

通过scanner输入季节， 然后使用switch判断季节

实现效果：

   

官方答案：

import java.util.Scanner;

   

public class HelloWorld {

    public static void main(String[] args) {

        Scanner s = new Scanner(System.in);

        System.out.println("请输入月份");

        int month = s.nextInt();

        String season;

        switch (month) {

        case 1:

        case 2:

        case 3:

            season = "春天";

            break;

        case 4:

        case 5:

        case 6:

            season = "夏天";

            break;

        case 7:

        case 8:

        case 9:

            season = "秋天";

            break;

        case 10:

        case 11:

        case 12:

            season = "冬天";

            break;

        default:

            season = "这是什么鬼~";

        }        

        System.out.println(season);

    }

}