How to put an object into an array

Question

How do I put an object into my array? This is my array.

public static Player [] playerArray;
Player[] playerArray = new Player [2];

player

public class Player {
    private String wpm;
    private String mistakes;
    private String time;

    public Player (String nwpm,String nmistakes, String ntime){
        wpm = nwpm;
        mistakes = nmistakes;
        time = ntime;
    }   

    public String getWPM(){
        return wpm;
    }
    public String getMistakes(){
        return mistakes;
    }
    public String getTime(){
        return time;
    }
}

I kept getting this error

Exception in thread "main" java.lang.NullPointerException

whenever I tried to use player. Did I do something wrong? Is there anything else you need?

Edit : adding where the errors happened

public void setPlayer1(Player p){
    p1WPM.setText("8");
    p1Mis.setText(p.getMistakes());
    p1Time.setText(p.getTime());
}

at which line the NullPointerException occur? You are declaring playerArray twice — Mohammad Faisal
– Mohammad Faisal, Commented Jan 21, 2016 at 5:55
show your main() method code.Also, why are you declaring playerArray twice? — Sabir Khan
– Sabir Khan, Commented Jan 21, 2016 at 5:56
how you are calling setPlayer1()? Add proper code not just snippets which can't be glued together — Mohammad Faisal
– Mohammad Faisal, Commented Jan 21, 2016 at 6:15

Atri · Accepted Answer · 2016-01-21 05:57:36Z

2

For example to add a Player object in array you can do:

Player[] playerArray = new Player [2];

//Create new Player object using the defined constructor
p = new Player("a","b","c");

// Assign p to 1st index of array
playerArray[0] = p;

answered Jan 21, 2016 at 5:57

Atri

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Comments

Mohammad Faisal · Accepted Answer · 2016-01-21 06:06:15Z

2

You have declared playerArray twice which is wrong. Also, you have not shown the code where you are getting the NullPointerException.

If you are newbie then try the below code:

Player[] playerArray = new Player [2]; //declare array of size 2
Player p1 = new Player("nwpm","nmistakes","ntime"); // first player object
Player p2 = new Player("nwpm","nmistakes","ntime"); // second player object

playerArray[0] = p1; // first player added in the array
playerArray[1] = p2; // second player added in the array

edited Jan 21, 2016 at 6:06

answered Jan 21, 2016 at 5:58

Mohammad Faisal

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Comments

Mohd Yunus · Accepted Answer · 2016-01-21 05:58:46Z

0

Player[] playerArray = new Player [2]; is creating the array, not the objects. You should add

 playerArray[0] = new Player(param1, param2, param3);
 playerArray[1] = new Player(param1, param2, param3);

to have all items have their object

answered Jan 21, 2016 at 5:58

Mohd Yunus

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Comments

Arsaceus · Accepted Answer · 2016-01-21 06:02:53Z

0

Try this:

  Player a = new Player("a","b","c");
            Player[] playerArray = new Player [2];
            playerArray = new Player[2];
            playerArray[0]=a;
            System.out.println(playerArray[0].getTime()+" "+playerArray[0].getMistakes()+" "+playerArray[0].getWPM());

Result: c b a

answered Jan 21, 2016 at 6:02

Arsaceus

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Comments

SatyaTNV · Accepted Answer · 2016-01-21 06:14:21Z

0

Exception in thread "main" java.lang.NullPointerException

Player[] playerArray = new Player [2];

With this statement you are just creating an array of size 2 whose all elements are null. But you are not creating elements here.

You have to instantiate each element.

for(int i=0; i< playerArray.length;i++)
    playerArray[i] = new Player();//with appropriate constructor

If you are trying to perform any operation on playerArray like playerArray[0].mistakes then get NullPointerException. You should initialize each element in the array with a Player object.

answered Jan 21, 2016 at 6:14

SatyaTNV

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Comments

Arsen Davtyan · Accepted Answer · 2016-12-02 00:40:31Z

Here is working code for you.

public class Player {
    public static final int SIZE = 2;
    public static Player[] playerArray = new Player[SIZE]; // Creates array of
                                                            // Player of size
                                                            // SIZE

    private String wpm;
    private String mistakes;
    private String time;

    public Player(String wpm, String mistakes, String time) {
        this.wpm = wpm;// this way is more readable
        this.mistakes = mistakes;
        this.time = time;
    }

    public String getWPM() {
        return wpm;
    }

    public String getMistakes() {
        return mistakes;
    }

    public String getTime() {
        return time;
    }

    public static void main(String[] args) {
        /*
         * If I wan to add something to the array it has to be object of the
         * array type and I need to create it first
         */

        // Create 2 Player objects
        Player player1 = new Player("p11", "p12", "p13");
        Player player2 = new Player("p21", "p22", "p23");

        // arrays are indexed from 0 to size-1
        playerArray[0] = player1;
        playerArray[1] = player2;

    }
}

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