Question

I get a NullPointerException when I run this. It occurs on the line listings[i].input();

Am I declaring this right? I want an array of 3 listing objects, input to them with my input() method, then output in reverse order.

public static void main(String[] args) {

    Listing[] listings = new Listing[3];

    for (int i = 0; i < listings.length; i++) {
        listings[i].input();
    }

    for (int i = listings.length - 1; i >= 0; i--) {
        System.out.println(listings[i]);
    }

}

Answer 1

You didn’t construct the individual Listing objects. So listings[0] == null. This is true for all elements of the array – they’re all initialized to null by default.

You must first say listings[i] = new Listing() or the like, before your listings[i].input().