Declaración de bucle si cambia elseif

***

## 基础if语句
*判断输入成绩是否及格*
import java.util.Scanner;

public class ifDemo02 {
    
    
    public static void main(String[] args) {
    
    
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入成绩：");
        int score = scanner.nextInt();
    if (score>=60){
    
    

    System.out.println("及格");

}else {
    
    
    System.out.println("不及格");
}

        scanner.close();
    }
}

## 基础esle if语句
*判断输入成绩是什么等级*
public class iFDemo03 {
    
    
    public static void main(String[] args) {
    
    
        Scanner scanner = new Scanner(System.in);
        System.out.println("请输入成绩：");
        int score = scanner.nextInt();
        if (score==100){
    
    

            System.out.println("恭喜满分");

        }else if(score<100 && score>=90){
    
    
            System.out.println("A");
        }else if (score<90 && score>=70){
    
    
            System.out.println("B");
        }else if (score<70 && score>=60){
    
    
            System.out.println("及格");
        }else if (score<60 && score>=0){
    
    
            System.out.println("成绩不及格");
        }else {
    
    
            System.out.println("格式错误");
        }
        scanner.close();
    }
}





## switch....case 案例比较
1.表达式是字符型
***
public class switchDemo01 {
    
    
    public static void main(String[] args) {
    
    

        char grade = 'A';
switch (grade){
    
    
    case 'A':
        System.out.println("优秀");
        break;
    case 'B':
        System.out.println("良好");
        break;
    case 'C':
        System.out.println("及格");
        break;
    case 'D':
        System.out.println("加油");
        break;
    case 'E':
        System.out.println("挂科");
        break;
    default:
        System.out.println("未知等级");
        break;
}

    }
}

## jdk7新特性 表达式可以是字符串。
2.字符串
public class switchDemo02 {
    
    
    public static void main(String[] args) {
    
    
        String name = "猜猜我是谁";
        switch (name){
    
    
            case "皮卡丘":
                System.out.println("皮卡丘");
                break;
            case"杰尼龟":
                System.out.println("杰尼龟");
                break;
            default:
                System.out.println("不知道");
        }
    }
}