Board.java

class Board {
    private int size;
    private int count;
    private char[][] board;

    Board() {}

    Board (int n) {
        size = n;
        count = n * n;
        this.board = new char[n][n];
    }

    public void setSize(int n) {
        size = n;
    }   
    
    // 0 means updated, 1 means won, 2 means draw, 3 means invalid move
    public int move(int x, int y, User user) {
        
        if (!isValid(x, y)) {
            printBoard();
            System.out.println("Invalid move! "+ x + " " + y);
            return 3;
        }

        board[x][y] = user.getMove();
        this.count--;
        
        printBoard();

        if (userWon(user, x, y)) {
            System.out.println(user.getName() + " won the game, well played!");
            return 1;
        }
        
        if (count==0) {
            System.out.println("The result is a draw!");
            return 2;
        }

        return 0;
    }

    private boolean userWon(User user ,int x ,int y) {
        boolean rowWin = true;

        // row check
        for(int i = 0; i < size; i++) {
            if (board[x][i] != user.getMove()) {
                rowWin = false;
            }
        }

        boolean colWin = true;
        for(int i = 0; i < size; i++) {
            if (board[i][y] != user.getMove()) {
                colWin = false;
            }
        }

        boolean diagWin1 = true;
        for(int i = 0; i < size; i++) {
            if (board[i][i] != user.getMove()) {
                diagWin1 = false;
            }
        }

        boolean diagWin2 = true;
        for(int i = 0; i < size; i++) {
            if(board[i][size-i-1] != user.getMove()) {
                diagWin2 = false;
            }
        }

        if(colWin || rowWin || diagWin1 || diagWin2) {
            return true;
        }

        return false;
    }

    private boolean isValid(int x, int y) {
        if(x < 0 || x >= size || y < 0 || y >= size || (int)(board[x][y]) !=0 ) {
            return false;
        }

        System.out.println();
        return true;
    }

    private void printBoard() {
        System.out.println("-----------");

        for(int i=0; i<size; i++){
            for(int j=0; j<size; j++){
                if(((int)board[i][j]) != 0)
                    System.out.print(" "+ board[i][j] +" ");
                else
                    System.out.print(" - ");
            }
            System.out.println();
        }

        System.out.println("-----------");
    }

}