用Java判断成绩等级

用户键盘输入成绩(百分制)，给出成绩的优、良、中、及和不及格等级（功能尽可能完善）

输入-1为退出。

public class text {

    public static void main(String args[]){

        Scanner scanner = new Scanner(System.in);

        System.out.println("请输入成绩：");
        double grade = scanner.nextDouble();

        if(grade > 100 || grade < 0){
            return;
        }else if(grade >= 90 && grade <=100){
            System.out.print("优");
        }else if(grade >= 80){
            System.out.print("良");
        }else if(grade >= 70){
            System.out.print("中");
        }else if(grade >= 60){
            System.out.print("及格");
        }else{
            System.out.print("不及格");
        }
    }
}

 public static void main(String[] args) {
        while (true) {
            double score = 0;
            Scanner scanner = new Scanner(System.in);
            System.out.println("请输入成绩:");
            score = scanner.nextDouble();
            if (score == -1) {
                System.out.println("系统即将关闭，欢迎下次再玩！");
                System.exit(0);
            }
            if (score > 100) {
                System.out.println("要上天？总分才100");
            } else if (score < 0) {
                System.out.println("食屎啦你,考负数？");
            } else if (score >= 90) {
                System.out.println("优");
            } else if (score >= 80) {
                System.out.println("良");
            } else if (score >= 70) {
                System.out.println("中");
            } else if (score >= 60) {
                System.out.println("及格");
            } else {
                System.out.println("不及格");
            }
        }


    }