Java: Encapsulation and array of objects

Question

I am making a tic-tac-toe game in Java to review some Java concepts and practice OOP. So far I have 4 classes: Board, Player, Coordinate, and Game. I am having problems testing the Board class. A board consists of an array of coordinates. There are currently two different constructor for Board. The constructor that takes a single Coordinate was mainly made for testing purposes.

Board.java

public class Board {

    private Coordinate squares;
    private Coordinate[] coordinateSet;

    public Board(Coordinate squares) {
        this.squares = squares;
    }

    public Board(Coordinate[] coordinateSet) {
        this.coordinateSet = coordinateSet;
    }

    public Coordinate getSquares() {
        return squares;
    }

    public Coordinate[] getCoordinates() {
        return coordinateSet;
    }

    public Coordinate getCoordinate(int i) {
        return coordinateSet[i];
    }
}

Coordinate.java

public class Coordinate {

    private int x;
    private int y;
    private int xFlag; // 0 if available, 1 if not available
    private int yFlag; // 0 if available, 1 if not available
    private boolean squareAvailability;

    public Coordinate(int x, int y, int xFlag, int yFlag) {
        this.x = x;
        this.y = y;
        this.xFlag = xFlag;
        this.yFlag = yFlag;
    }

    public int getXCoordinate() {
        return x;
    }

    public int getYCoordinate() {
        return y;
    }

    public int getXFlag() {
        return xFlag;
    }

    public int getYFlag() {
        return yFlag;
    }

    public void setXFlag() {
        if(xFlag == 0) {
            xFlag = 1;
        } else { }
    }

    public void setYFlag() {
        if(yFlag == 0) {
            yFlag = 1;
        } else { }
    }

    public void add(Coordinate coordinate) {
        // TODO Auto-generated method stub

    }

    public boolean isSquareAvailable(Coordinate coordinate) {
        if(coordinate.getXFlag() == 0) {
            if(coordinate.getYFlag() == 0) {
                squareAvailability = true;
            } else {
                squareAvailability = false;
            }
        } else {
            squareAvailability = false;
        }       

        return squareAvailability;
    }

}

BoardTest.java

import edu.learning.tictactoe.Board;
import edu.learning.tictactoe.Coordinate;

public class BoardTest {

    public static void main(String[] args) {
        Coordinate[] coordinates = new Coordinate[9];   
        Coordinate coordinate = new Coordinate(0, 0, 0, 0);
        for(int i = 0; i < 3; i++) {
            for(int j = 0; j < 3; j++) {
                coordinates[i + j] = new Coordinate(i, j, 0, 0);
            }
        }
        Board board = new Board(coordinate);
        System.out.println(board.getSquares().getXCoordinate());
        Board board2 = new Board(coordinates);
        System.out.println(board2.getCoordinates().getCoordinate(0).getXCoordinate()); // error
    }
}

I get an error on the last line of BoardTest.java in my IDE that I Cannot invoke getCoordinate(int) on the array type Coordinate[]. The problem is that I am trying to return a Coordinate object from an array of Coordinate objects, which isn't possible(?) So how would I return a Coordinate from an array of Coordinates?

Answer 1

board.getCoordinates() returns an array and the compiler error tells you that this array does not have a method getCoordinate(int).

Simply write

board.getCoordinate(0).getXCoordinate()

if you want to access the coordinate via the array you could write

board.getCoordinates()[0].getXCoordinate()