Getting error that my array might not be initialized. I'm trying contain all prime numbers within a given number into an array.

Question

import java.util.Scanner;
class Program {
public static int isPrime(int a) {
int sum=0;
for(int i=1;i<=a;i++) {
if(a%i==0) {
sum+=i;
}
}
if(sum==a+1) return 1;
else return 0;
}
public static void main(String[] args) {
int arr[];
int j=0;
Scanner sc =new Scanner(System.in);
int x =sc.nextInt();
for(int i =2;i<x;i++) {
if(isPrime(i)==1) {
arr[j]=i;
j++;
}
}
for(int k=0;k<arr.length;k++) {
System.out.println(arr[k]);
}
}
}

Answer 1

Since the array has not been initialized it does not have a size/nothing stored in memory for the variables.

You could do something like:

// At this spot:
int x = sc.nextInt();

arr = new int[x];
// this is what you need

Something along those lines.

Also your isPrime method might as well be a boolean instead of int.

Answer 2

Thanku Rrestoring faith but giving a dimension length to the array as x(which is the input number ) will far exceed the length of the array that I intend to create. Because obviously the number of prime numbers(j) will be less than the number(x) itself.