Question

Possible Duplicate:
objects classes and arrays – why is it returning ‘null’ ? [java]

The other questions with similar titles all have the answer that their data needs to be initialized which I have done but I’m still getting a null pointer exception. Could anyone tell me why?

    public class grid{
private Node [][] board = new Node [9][9];

public boolean add(int x, int y, char label) {
    boolean valid=true;

    System.out.println("enter add");
    if(label==' '){
        System.out.println("enter if 1");
        board[x][y].setValue('0');
    }
    else if(label<='9'&&label>'0'){
        System.out.println("enter if 2");
        board[x][y].setValue(label);
    }
    else{
        valid=false;
    }
    if(valid)
        System.out.println("valid");
    return valid;
}

I’m getting the error on the setValue Lines (10 and 14)

    public class Node{
public char value;
public char []  possibleValues = {1,2,3,4,5,6,7,8,9};
public boolean correct=false;
    }

Edit: I figured it out, if anyone else has the same problem, this seems to fix it.

    if(label==' '){
        System.out.println("enter if 1");
        board[x][y]= new Node(' ');
    }
    else if(label<='9'&&label>'0'){
        System.out.println("enter if 2");
        board[x][y]= new Node(label);
    }

Answer 1

An array does not initialize the elements of the array. So, each board[x][y] will be initially null.