public void judgedScore(){
   BufferedReader br = null;
    try{
        System.out.println("请输入成绩，并回车：");
        br = new BufferedReader(new InputStreamReader(System.in));
        String line = br.readline();
        //做非法字符的判断，不是数字的等，这里就判断null和空字符
        if(line == null || "".equals(line.trim())){
            System.out.println("你录入的是非法字符，继续Y，其它建退出！");
            br = new BufferedReader(new InputStreamReader(System.in));
            line = br.readline();
        }

        if(!"y".equalsIgnoreCase(line)){
            return;
        }

        int score = Integer.parseInt(line.trim());
        if(score > 100 || score < 0){
            System.out.println("录入的是不符合逻辑的数值，继续Y，其它建退出！");
            br = new BufferedReader(new InputStreamReader(System.in));
            line = br.readline();
        }
        if(!"y".equalsIgnoreCase(line)){
            return;
        }
        int flag = 0;
        if(score >= 90){
            flag = 1;
        }else if(score >= 80){
            flag = 2;
        }else if(score >= 70){
            flag = 2;
        }else if(score >= 60){
            flag = 3;
        }else {
            flag = 4;
        }
        switch(flag){
            case 1:
                    System.out.println("你的成绩登记是A");
                    break;
            case 2:
                    System.out.println("你的成绩登记是B");
                    break;
            case 3:
                    System.out.println("你的成绩登记是C");
                    break;
            case 4:
                    System.out.println("你的成绩登记是D");
                    break;
            default:
                System.out.println("成绩无效！");
        }

        System.out.println("是否继续录入？继续Y，其它建退出！");
        br = new BufferedReader(new InputStreamReader(System.in));
        line = br.readline();
        if("y".equalsIgnoreCase(line)){
            judgedScore();
        }
    }catch(Exception e){

    }
}