Accessing object-type methods from an object array java

Question

My problem is I'm trying to make a console based chess game. Starting off with an Object array to hold the squares of the chess board.

class Chessboard {
    Object[][] board = new Object[10][10];

I fill it out perfectly with various if-sentences like this:

for (int i = 0; i < 10; i++) {
    for (int j = 0;j < 10; j++) {
        if a position on a chess demands a specific piece:
                 board[i][j] = new ChessPiece(String firstLetterOfPiece, i, j);
        else fill in blanks:
                 board[i][j] = new ChessPiece(" ", i,j);
    }
}

Now, I have some find position methods in the ChessPiece class that just gives a compiler error when I try it from the class Chessboard.

What I do is: (to test)

System.out.println(board[2][4].getXposition());

I get "Cannot find symbol". What can I do to avoid this?

Post the exact message: what symbol can't it find? What's that extraneous String doing in your pseudocode in the new ChessPiece ctor call? — Dave Newton
– Dave Newton, Commented Nov 19, 2011 at 15:59
Why can't you use ChessPiece[][] board = new ChessBoard[10][10]? And why are you using a 10x10 grid? A "moat" doesn't make a lot of sense here. — NullUserException
– NullUserException, Commented Nov 19, 2011 at 16:02
Can't find method getXpos(). Because java looks in Object-class. The string is to identify the chesspiece. Also, I believe that using a Objectarray I can mix different classes which is a bit easier when it comes to displaying integers and letters. (The sides, top and bottom of the chessboard) — mr2k
– mr2k, Commented Nov 19, 2011 at 16:13

corsiKa · Accepted Answer · 2011-11-19 16:00:39Z

1

Well, you could "cast" it, for example: ((ChessPiece)(board[2][4])).getXposition()

But I would recommend doing something different: make a ChessSquare class that can hold a ChessPiece, or not.

Then go

ChessSquare square = board[2][4];
if(square.hasPiece()) {
    ChessPiece piece = square.getPiece();
    return piece.getXposition();
}

answered Nov 19, 2011 at 16:00

corsiKa

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Comments

Chris · Accepted Answer · 2011-11-19 16:01:21Z

0

Firstly, if your array will only ever contain ChessPiece objects, declare it as

ChessPiece[][] board = new ChessPiece[10][10];

Secondly, since your array elements can be null, you'll want to do a null check before calling any methods:

if(board[2][4] != null)  System.out.println(board[2][4].getXPosition());

answered Nov 19, 2011 at 16:01

Chris

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1 Comment

mr2k Over a year ago

Thanks, though I throw in some integers and strings to display a through h and 1 through 8. :)

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