Question

I am doing java programming practice from a website. I have to display this out put using arrays.

Enter the number of students: 3
Enter the grade for student 1: 55
Enter the grade for student 2: 108
Invalid grade, try again...
Enter the grade for student 2: 56
Enter the grade for student 3: 57
The average is 56.0

This is my source code so far, it is raising error The local variable grades may not have been initialized. How do I recover this? I have to make this program using arrays.

package array;

import java.util.Scanner;

public class GradesAverage {

    public static void main(String[] args) {

        int numStudents = 0;
        int[] grades;

        Scanner in = new Scanner(System.in);

        System.out.print("Enter number of students : ");
        numStudents = Integer.parseInt(in.next());

          for (int i = 0; i < numStudents; i++) {
              System.out.print("Enter grade of student "+i+" :");
              grades[i] = Integer.parseInt(in.next());
        }

    }

}

Answer 1

When you write

int[] grades;

you declare a variable called grades, that can hold a value of type int[]. However, before you can use it you also have to initialize it, eg create the actual data structure. This is done like this:

int[] grades = new int[numStudents];

Note that you need to know the size beforehand when you declare an array, so you will have to move the creation of the array to just before the for loop.