java输入分数显示等级

package zzz;
import javax.swing.JOptionPane;
import java.util.*;
public class llyytt {

 
 public static void main(String[] args) {
  Scanner input=new Scanner(System.in);
  char grade;
  String num=JOptionPane.showInputDialog(null,"请输入一個分数:","梁燕婷",JOptionPane.QUESTION_MESSAGE);
  int aa=Integer.parseInt(num);
  // TODO Auto-generated method stub
   if(aa>=80)
    grade='A';
   else if(aa>=70)
    grade='B';
   else if(aa>=60)
    grade='C';
   else
    grade='D';
   JOptionPane.showMessageDialog(null,grade,"梁燕婷",JOptionPane.INFORMATION_MESSAGE);
    System.out.print((aa*100)/100.0);
 }
}