简单的成绩判定

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import java.util.Scanner;
public class Stu{
public static void stuGrade(){
?Scanner input = new Scanner(System.in);
?String [] standard = {"E","G","M","F"};
?String [] grade = {"优秀","良好","中等","不合格"};
?messageshow("请输入学生状况:");
?String stu ;
?boolean judge = false;
?stu = input.next();
?for(int i = 0 ; i < standard.length ; i ++){
??if( stu.equals (standard [i])){
???System.out.println(grade [i]);
????judge = true;
????break;
???}
?}
??if(judge == true){
???messageshow("继续Y/N");
???String str = input.next();
???if(str.equals("Y"))
????stuGrade();
???else{
????messageshow("退出系统");
???}
??}??
??if(judge == false){
???messageshow("输入非法");
??}
}
public static void messageshow(String str){
?System.out.print(str);
}
?public static void main(String [] args){
??stuGrade();
?}
}