Find a max sub-array in array

You need the indices to specify the range, not the real values of the array.
Also, copyOfRange range is from first element to last+1

You could do this:

import java.util.Arrays;

public class lol{

    static String maxSubArraySum(int[] a, int size)
    {
        int max_so_far = a[0];
        int curr_max = a[0];
        int curr_max_idx = 0;
        int max_so_far_idx = 0;
        for (int i = 1; i < size; i++)
        {
            curr_max = Math.max(a[i], curr_max+a[i]);
            if(curr_max==a[i]){
                curr_max_idx = i;
            }
            max_so_far = Math.max(max_so_far, curr_max);
            // i+1 to end at last + 1
            if(max_so_far==curr_max){
                max_so_far_idx = i + 1;
            }
        }
        int [] res = Arrays.copyOfRange(a, curr_max_idx, max_so_far_idx);
        return Arrays.toString(res);
    
    }
    
    public static void main(String[] args)
    {
        int a[] = {-2, -3, 4, -1, -2, 1, 5, -3};
        int n = a.length;
        String arr = maxSubArraySum(a, n);
        System.out.println("Result is " + arr);
    }
}

or instead of Math.max() function, just use if statements and update curr_max and its index curr_max_idx