JAVA - Object cannot be added to Object Array - NullPointerException [duplicate]

Question

I am initializing an Object(Bateau), which contains within it an array of objects (Element) called elements.

Upon calling the constructor, I want to create several elements for a "bateau" object.

The number of elements vary depending on which kind of "bateau" it is because "Bateau" has 3 sub-classes which determine the number of elements to initialize.

I get a NPE when I try to add a new Element to elements, can anyone help me resolve this issue ?

public class Bateau {
private boolean horizontal = false;
protected Element[] elements;

public Bateau(int pX, int pY, boolean horizontal, int nombreElements) {
    this.horizontal = horizontal;
    for (int i = 0; i < nombreElements; i++) {
        if (this.horizontal) {
            //NullPointerException elements[i] not initialized ?
            this.elements[i] = new Element((pX + i), pY);
        } else {
            this.elements[i] = new Element(pX, (pY + i));

        }
    }
}}

where do you think the array initialization occurs? some reading: stackoverflow.com/questions/25761646/… — user180100
– user180100, Commented Jan 30, 2015 at 16:28
I added: elements = new Element[nombreElements]; in my constructor. — beln
– beln, Commented Jan 30, 2015 at 16:31

Peter Lawrey · Accepted Answer · 2015-01-30 16:28:48Z

4

In your debugger you would be able to see that

Element[] elements = null;

I suggest you initialise it with

elements = new Element[nombreElements];

answered Jan 30, 2015 at 16:28

Peter Lawrey

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