ArrayList add null pointer

Question

The following class keeps giving me a null pointer when I try to call the addPlayer method and I have no idea what the heck I'm doing wrong. : Keep in mind this is really simple stuff...supposedly... I'm learning Java.

import java.util.*;

public class Team {

    private String teamName;
    private  ArrayList<Player> players;
    private int numberOfPlayers; 

    public Team(String teamName) {

        this.teamName = teamName;

    }

    public String getName() {

        return this.teamName;

    }

    public void addPlayer(Player player) {
        this.players.add(player);
        }


    public void printPlayers() {

        for (Player player : this.players) {
            System.out.println(player);
        }
    }
}

Here is the Player class :

public class Player {

    private String name;
    private int goals;

    public Player(String name) {
        this.name = name;
    }

    public Player(String name, int goals) {

        this.name = name;
        this.goals = goals;
    }

    @Override
    public String toString() {

        return this.getName() + ", goals " + this.goals();
    }

    public String getName () {
        return this.name; 
    }

    public int goals() {
        return this.goals; 
    }

}

possible duplicate of What is a Null Pointer Exception, and how do I fix it? — user289086
– user289086, Commented Jun 23, 2014 at 18:12

Ryan J · Accepted Answer · 2014-06-23 18:06:00Z

9

This is your problem:

private  ArrayList<Player> players;

is not initialized, you never create a new one when you instantiate your class.

Add the following to your constructor:

public Team(String teamName) {

    this.teamName = teamName;
    this.players = new ArrayList<Player>();

}

answered Jun 23, 2014 at 18:06

Ryan J

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Comments

Frement · Accepted Answer · 2014-06-23 18:05:21Z

6

You haven't initialized the variable, thus its value is null.

private  ArrayList<Player> players = new ArrayList<Player>();

That should fix it.

answered Jun 23, 2014 at 18:05

Frement

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1 Comment

user3690146 Over a year ago

Oh wow.... i have been mucking with this thing for 2 hours trying to get it to quit giving me null pointer.... LOL Thank you!

SparkOn · Accepted Answer · 2014-06-23 18:14:44Z

2

You have declared an ArrayList but where is the initialization?? Fix it by initializing the ArrayList as :

private  ArrayList<Player> players = new ArrayList<Player>();

answered Jun 23, 2014 at 18:14

SparkOn

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