Couldn't find Java bug

Question

import java.util.*;
class Grade {
private int id;
private String name;
public int exam_number;
private double SCORE = 0;
private String GRADE;
Grade(int i, String n, int en){
this.id = i;
this.name = n;
this.exam_number = en;
}
public void take_exam(){
Scanner sc = new Scanner(System.in);
int i = exam_number;
while(i>0){
System.out.println("Enter the obtained score");
double val = sc.nextDouble();
if(val<0 || val>100){
System.out.println("Please Enter between and including 0 and 100");
continue;
}else{
SCORE += val;
}
}
double average = (SCORE/exam_number);
void calc(){
if(average>=0.9){
GRADE = "A";
}
else if(average>=0.8){
GRADE = "B";
}
else if(average>=0.7){
GRADE = "C";
}
else if(average>=0.6){
GRADE = "D";
}
else{
GRADE = "F";
}
}
String gGrade(){
return Grade;
}
public static void main(String [] args){
Grade Gr = new Grade(12,"Adugna",3);

Answer 1

Add all your code in playground to be more readable
and attach here the link