NullPointerException when attempting to access array of objects

Question

I am writing Java code for a Monopoly game and I am getting a NullPointerException on the line with the SetPlayerName(tempName, numPlayersCounter); method call. This method sets the name of a Player in a Player array. When the program is run, the console says that the value of numPlayersCounter is 1, the length of the Player array playersArr is 3.

        sc2.ok1Button.addActionListener(new ActionListener() //middle ok button
    {
        public void actionPerformed(ActionEvent e)
        {
            System.out.println("Name ok button pressed");
            System.out.println("Name is:" + sc2.nameField.getText());
            String tempName = sc2.nameField.getText();
            System.out.println("numPlayersCounter value: " + numPlayersCounter);

            SetPlayerName(tempName, numPlayersCounter);
            System.out.println("Player " + numPlayersCounter + "name: " +playersArr[numPlayersCounter].GetName());
            sc2.EnableName(false);
            sc2.EnablePieces(true);


        }
    });

The method SetPlayerName is defined as:

    public static void SetPlayerName(String n, int id)
    {   playersArr[id].SetName(n);    }

and playersArr is declared before the constructor and main as:

    protected static Player [] playersArr; //player 0 is the bank

In Player.java, the name is set as an empty string in the constructor and the SetName method is defined as:

    public void SetName(String n)
    {   name = n;   }

I have tried to set the name directly from the actionPerformed method and incrementing a different Player variable. The problem seems to be with accessing the correct array element, but it should be accessing element 1 of an array of length 3.

What do I need to do to fix this? Any help would be greatly appreciated.

possible duplicate of [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it) — jdphenix, Apr 20 '15 at 02:46
You never initialize your array `playersArr` (so it is `null`). — Elliott Frisch, Apr 20 '15 at 02:47
_"What do I need to do to fix this?"_ change to something like `protected static Player [] playersArr = new Player[10];` but I would recommend you to use `ArrayList` instead of `array` — DnR, Apr 20 '15 at 02:51
I initialize it in my constructor and then point playersArr to a new array in a previous actionPerformed method. Sorry I didn't add that before. I will update my question to include this. — Laura Ann Truax, Apr 20 '15 at 02:52
@jdphenix, I was looking at that post earlier and I was not able to use it to my advantage — Laura Ann Truax, Apr 20 '15 at 02:56
@DnR initializing when I declare the array is not working either. I will look into the ArrayList. — Laura Ann Truax, Apr 20 '15 at 02:59
@Baby, the value being passed into id is 1 and the length of the array is 3 (according to the console when the program is run), so 1 should be a valid location — Laura Ann Truax, Apr 20 '15 at 03:02
try printing the array content at the same location you print the array length: `System.out.print(Arrays.toString(playersArr));` what is the output? — Baby, Apr 20 '15 at 03:05
@Baby you were right! The output is [null, null, null] . Now I need to find out why playersArr = new Player[numPlayers+1]; dosen't initialize 3 new Player objects. — Laura Ann Truax, Apr 20 '15 at 03:19
have you tried just `new Player()`?. you don't have to define a default constructor. default constructor is exist by default — Baby, Apr 20 '15 at 03:27
I changed the constructor to a default constructor (parameters were not necessary) and Gary posted the answer I was looking for. Thank you too, Baby. You helped me a lot! — Laura Ann Truax, Apr 20 '15 at 03:31

score 0 · Answer 1 · answered Apr 20 '15 at 02:53

0

From what is given, you have not initialized your playersArr array. On the line:

protected static Player [] playersArr;

or anytime because you call the SetPlayerName() method you need to initialize it. For example:

protected static Player [] playersArr = new Player[]{/*Stuff in array*/};

answered Apr 20 '15 at 02:53

Forseth11

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Make sure you do not have anything in your code setting playerArr to null and can you show me what you have changed? – Forseth11 Apr 20 '15 at 03:08
Turns out the array was initialized, but the individual Player objects were not. Thank you for your input. – Laura Ann Truax Apr 20 '15 at 03:48

Gready · Accepted Answer · 2015-04-20T03:05:53.203

0

Reason:

You have an empty array list, i.e., playerArr[0] = null; and your SetPlayerName method references playerArr[id] which contains a null pointer.

Fix:

You need to add Player objects to your playerArr before trying to use them, try this:

playerArr[numPlayersCounter] = new Player();
SetPlayerName(tempName, numPlayersCounter);

You should also initiate the playerArr too, with 3 elements...:

protected static Player[] playerArr = new Player[3];

edited Apr 20 '15 at 03:05

answered Apr 20 '15 at 02:56

Gready

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1

That is exactly what needed to happen (with the exception of playerArr being playersArr , with an s). Thank you very much @gary-read – Laura Ann Truax Apr 20 '15 at 03:28

score 0 · Answer 3 · edited Apr 20 '15 at 03:24

0

Have you initialized the Player?

playersArr[numPlayersCounter] = new Player();

and then

SetPlayerName(tempName, numPlayersCounter);

edited Apr 20 '15 at 03:24

Dyrandz Famador

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answered Apr 20 '15 at 03:06

Suspended

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That was the problem. I chose Gary's answer though because he had answered earlier. Thank you for your help. – Laura Ann Truax Apr 20 '15 at 03:50

NullPointerException when attempting to access array of objects

3 Answers3

Reason:

Fix: