Null pointer exception for Array of Objects

Question

I am new to using arrays of objects but can\'t figure out what I am doing wrong and why I keep getting a Null pointer exception. I am trying to create an Theatre class with

Answer 1

You are not creating an spotlight objects.

arrayOfSpotlights =  new spotlight[N];

This just creates an array of references to spotlights, not the objects which are referenced.

The simple solution is

for (int i = 0; i < arrayOfSpotlights.length; i++) { 
    arrayOfSpotlights[i] = new spotlight();
    arrayOfSpotlights[i].turnOn();          
}

BTW You should use TitleCase for class names.

You could write your class like this, without using cryptic code like 0 and 1

public class Spotlight {
    private String state;

    public Spotlight() {
        turnOff();
    }

    public void turnOn() {
        state = "on";  
    }

    void turnOff() { 
        state = "off";
    }

    public String toString() {
        return "is " + state;
    }
}