Question

I don’t understand why this is giving me a null pointer exception when I try to add a value to the a1[i] array.

public class Array {

String text;
int total = 0, count = 0;

Array[] a1 = new Array[100];
Scanner scan = new Scanner(System.in);



public void setData() {
    int i=0;

    System.out.println(a1.length);
    do {

        System.out.println("Enter some data: ");
        text = scan.next();
        if (text.equals("end"))break;
        a1[i].text = text; //I get a null pointer exception here. Not sure why. 
        i++;

    } while (true);

    }

Answer 1

Everything initialized in the a1 array is null. You’d have to put a new instance of Array() in there before doing anything with the member methods.

What this translates to: Every time you want to do something with a1[i], you’d have to have a new instance of Array in there first.

Example:

for(int i = 0; i < n; i++) {
    a1[i] = new Array();
}