利用Java实现对“A”到“E”的评级可以循环输入

import java.util.Scanner;
public class One {
    public static void main(String[] args) {
        System.out.println("请输入一个分数");
        //定义一个分数“grade（分数） ”且会有小数；
        double grade;//可有可无（Java默认为【double】
        while (true){
        Scanner scanner = new Scanner(System.in);
        grade = scanner.nextDouble();
        //判断是否有误
        if (grade < 0 || grade > 100) {
            System.out.println("输入有误");
            System.exit(0);
        }
            //判断分数等级
            if (grade >= 90) System.out.println("this mark is grade 'A' ");
            else if (grade >= 80) System.out.println("this mark is grade 'B' ");
            else if (grade >= 70) System.out.println("this mark is grade 'C' ");
            else if (grade >= 60) System.out.println("this mark is grade 'D' ");
            else System.out.println("this mark is grade 'E' ");
        }

    }
}