How to fix an array method throwing a NullPointerException in Java?

Question

I am trying to make an array of video games. I wanted to implement an array method that will add a new game to the array if there is an available index that is null. however when I try to implement such a method. It throws a NullPointerException.

Here is the code in the main method:

public static void main(String[] args) {
        Game[] arr = new Game[3];
        Game t1 = new Game("The Walking Dead", 2012, "Telltale games");
        Game t2 = new Game("The Wolf Among Us", 2014, "Telltale games");
        Game t3 = new Game("Half-Life 2", 2007, "Valve");
        
        try {
            arr[2].addGame(t3);
        } catch(NullPointerException e) {
            System.out.println("Caught NullPointer");
            arr[0] = t1;
        }
        System.out.println(arr[0]);
    }

And here is the method I have implemented in the "Game" class:

public Game addGame(Game game) {
        //TODO
        for(int i = 0; i < arr.length; i++) {
            try {
                if(arr[i] == null) {
                    arr[i] = game;
                }
            } catch(NullPointerException e) {
                System.out.println("Caught exception");
                arr[i] = game;
                return arr[i];
            }
        }
        return game;
    }

I am very lost and I don't understand how it is throwing the nullpointerexception when I am explicitly trying to check for null to try and insert a new "Game" into the empty index. Any help is much appreciated! Thanks!

`Game[] arr = new Game[3];` creates an empty array, so each element in the array is `null`. You need to assign a value to the array, ie `arr[0] = new Game("The Walking Dead", 2012, "Telltale games");`. You should also check each element to determine if it's been assigned, ie `arr[0] != null` before trying to access it — MadProgrammer, Apr 10 '21 at 23:59

score 0 · Answer 1 · answered Apr 10 '21 at 23:57

I would suggest instead using a List here:

List<Game> games = new ArrayList<>();
Game g1 = new Game("The Walking Dead", 2012, "Telltale games");
Game g2 = new Game("The Wolf Among Us", 2014, "Telltale games");
Game g3 = new Game("Half-Life 2", 2007, "Valve");
games.add(g1);
games.add(g2);
games.add(g3);

The problem with using an array Game[] is that it can be a hassle to add a new item to the end, due to not knowing where the end is, and also what size is available. Lists avoid these problems.

Thank you! Was just trying to see how far I could push a normal array, but I guess it does have its limits. Thank you for your answer! Have a good day — Ty Strong, Apr 11 '21 at 13:37

How to fix an array method throwing a NullPointerException in Java?

1 Answers1