Why do I get an ArrayIndexOutOfBoundsException in this prime number check?

Question

I was finding out highest prime factor which divides num, as shown in program, there\'s a issue with array and

arr[j] = i;
j++;

Excepti         


        

Answer 1

Looks like you start j = 1 and your array only has one element in it to begin, so on the first pass through your for loop you look for arr[1], but the first element in an array is at arr[0]. Java arrays are zero indexed meaning if you have 10 elements in the array they are located in arr[0] to arr[9].