java.lang.NullPointerException error. How to initialize class?

Question

I am pretty new to java and I am trying to write a simple game but I am getting this error in my program "java.lang.NullPointerException" couldn't figured out why I am getting this so I am posting my code here.

    public static void main(String[] args) {
       Scanner console = new Scanner(System.in);
       System.out.println("How many players?:");
       int t = console.nextInt();
       Player p[] = new Player[t];
       for(int i=0; i<t; i++){
           System.out.println("Player " + i+1 + " enter your name:");
           p[i].player_name = console.nextLine();
           System.out.println(p[i].player_name + " Easy(1), Medium(2), Hard(3), enter one integer");
           p[i].number = console.nextInt();
           System.out.println("Player " + i+1 + "name: " + p[i].player_name + "your integer is " + p[i].number);
      }
   }

And this is my Player class

public class Player {
   public String player_name;
   public int number;

   public Player() {
       this.player_name = " ";
       this.number = 0;
   }
}

at the beginning of your loop you need to add p[i] = new Player(); — Logan Murphy
– Logan Murphy, Commented Mar 21, 2014 at 20:15

Reimeus · Accepted Answer · 2014-03-21 20:24:01Z

4

Array elements of Object types are null by default. Create an instance of Player before attempting to assign its fields

for (int i=0; i<t; i++) {
   p[i] = new Player();
   ...
}

edited Mar 21, 2014 at 20:24

answered Mar 21, 2014 at 20:15

Reimeus

160k16 gold badges225 silver badges282 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

skiwi · Accepted Answer · 2014-03-21 20:15:25Z

2

You need to initialize your p[i] first. You can put this at the start of the for-loop inside the loop:

p[i] = new Player();

answered Mar 21, 2014 at 20:15

skiwi

69.8k32 gold badges140 silver badges225 bronze badges

Comments

Ra Mon · Accepted Answer · 2014-03-21 20:16:06Z

0

Here you make an array of players but you dont fill it with a player

Player p[] = new Player[t];

do this in you loop first

p[i] = new Player();

answered Mar 21, 2014 at 20:16

Ra Mon

1273 bronze badges

Comments

Tomasz Bekas · Accepted Answer · 2014-03-21 20:18:53Z

0

The only thing that this statement does

Player p[] = new Player[t];

is just allocating memory for t references to the Player objects. It does not initialize any Player object, so these references referes to null objects, therefore when you invoke

p[i].player_name

you get the NullPointerException.

answered Mar 21, 2014 at 20:18

Tomasz Bekas

6961 gold badge6 silver badges17 bronze badges

Comments

Alejandro Baltra · Accepted Answer · 2014-03-21 20:20:54Z

0

You are missing the instantiation of the new player objects inside the for loop. When you declare the array with: Player p[] = new Player[t];, you are just creating the array of type Player. Before assigning values inside the loop, instantiate an object in the proper position of the array. i.e:

for (int i = 0; i < t; i++) {
   p[i] = new Player();
}

answered Mar 21, 2014 at 20:20

Alejandro Baltra

685 bronze badges

Collectives™ on Stack Overflow

java.lang.NullPointerException error. How to initialize class?

5 Answers 5

Comments

Comments

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

Comments

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related