1 public class TestWin{
2 public static void main(String[] args){
3 int n;
4 hexagon[][] board;
5
6 n = 4;
7 board = new hexagon[n][n];
8 board[0][0].value = 'R';
Hi. javac doesn't like what I did on line 8. Does anyone know why?
It's been a while since I've so much as looked at Java, but have you tried doing this first?
board[0][0] = new hexagon(); // or whatever its constructor is
Spot on kwatford. All you have done with line 7 is to tell java to create space for n*n Hexagon objects in a 2 dimensional array.
You will still need to call new for each of these Hexagons
Essentially, you need to replace line 7 with something like:
board = new Hexagon[n][n];
for(int i=0; i<n; i++)
for(int j=0; j<n; j++)
board[i][j] = new Hexagon();
Short Answer:
As kwatford said what you need to do is this:
board[0][0] = new hexagon(); // or whatever its constructor is
Longer Explanation:
Just to expand further. Your 2D array is; an array of pointers (or references in Java). This is what one row of the array will look like immediately after this call board = new hexagon[n][n];:
0 1 2 3 4 5 // column index, row index = 0
-------------------------------------------
| | | | | | | | | | // value
--- | ----- | ----- | ---------------------
| | | ...
| | |
| | |
| | |
| | v
| | Null
| v
| Null
v
Null (This means that it points to nothing)
You tried:
board[0][0].value = 'R';
which is the same as this:
null.value = 'R';
You have initialized your array using this line:
board = new Hexagon[n][n];
But you still need to initialize the elements in your array. This would initialize the first three:
board[0][0] = new hexagon(); // or whatever its constructor is
board[1][0] = new hexagon(); // or whatever its constructor is
board[2][0] = new hexagon(); // or whatever its constructor is
Which would result in an array that looks like this:
0 1 2 3 4 5 // column index, row index = 0
-------------------------------------------
| | | | | | | | | | // value
--- | ----- | ----- | ---------------------
| | |
| | |
| | |
| | |
| | v
| | An instance of type Hexigoon (what you get when you type new Hexigon)
| v
| An instance of type Hexigon (what you get when you type new Hexigon)
v
An instance of type Hexigon (what you get when you type new Hexigon)
I remember banging my head on the table with this exact problem two years ago. I love stackoverflow
To expand on what kwatford said, initializing an array in java gives you nulls if the array type is an object. If you had a raw array, such as an array of doubles, you would start with 0 as the entry for each element of the array.
.value()would be a method that is defined in the Hexagon class.