keep getting java.lang.nullpointerexception?

public void TicTacToe()  
{
    board = new char[3][3];
    for(int r = 0; r < 3; r++)  
    {
    for(int c = 0; c < 3; c++)
    board[r][c] = ' ';
    }
    xTurn = true;
    keyboard = new Scanner(System.in);
}
private void displayRow(int row)  
{
    System.out.println(" " + board[row][0] + " | " + board[row][1] + " | " + board[row][2]);
}   
private void displayBoard()  
{
    displayRow(0);
    System.out.println("-----------");
    displayRow(1);
    System.out.println("-----------");
    displayRow(2);
}
private void displayMenu()  
{
    if(xTurn)
        System.out.println("X's Turn!");
    else
        System.out.println("O's Turn!");        
    System.out.println("What would you like to do?");
    System.out.println("1: Make a move");
    System.out.println("2: Start Over");
    System.out.println("3: Quit");
    System.out.print("Choice: ");
}
private boolean getMove()  
{
boolean invalid = true;
int row = 0, column = 0;
while(invalid)  
{
    System.out.println("Which row, column would you like to move to? Enter two numbers between 0-2 separated by a space to indicate position.");
    row = keyboard.nextInt();
    column = keyboard.nextInt();
    if(row >= 0 && row <= 2 && column >= 0 && column <= 2)  
    {
    if(board[row][column] != ' ')
    System.out.println("That position is already taken");
    else
    invalid = false;
    }
    else
    System.out.println("Invalid position");
    }
    if(xTurn)
        board[row][column] = 'X';
    else
        board[row][column] = 'O';

    return winner(row,column);
    }
private void restart()  {
    for(int r = 0; r < 3; r++)  
    {
    for(int c = 0; c < 3; c++)
            board[r][c] = ' ';
    }
    xTurn = true;
    }
    private boolean winner(int lastR, int lastC)  
    {
    boolean winner = false; 
    char symbol = board[lastR][lastC]; 
    int numFound = 0;
    for(int c = 0; c < 3; c++)  {
    if(board[lastR][c] == symbol)
            numFound++;
    }

    if(numFound == 3)
    winner = true;
    numFound = 0;
    for(int r = 0; r < 3; r++)  {
    if(board[r][lastC] == symbol)
    numFound++;
    }

    if(numFound == 3)
    winner = true;
    numFound = 0;
    for(int i = 0; i < 3; i++)  {
    if(board[i][i] == symbol)
    numFound++;
    }

    if(numFound == 3)
    winner = true;

    numFound = 0;
    for(int i = 0; i < 3; i++)  {
    if(board[i][2-i] == symbol)
    numFound++;
    }

    if(numFound == 3)
    winner = true;

    return winner;
    }
    private boolean boardFull()  {
    int numSpotsFilled = 0;

    for(int r = 0; r < 3; r++)  {

    for(int c = 0; c < 3; c++)  {
    if(board[r][c] == 'X' || board[r][c] == 'O')
    numSpotsFilled++;
    }
    }

    return numSpotsFilled == 9;
    }
    public void play()  {

    while(true)  {

    displayBoard();
    displayMenu();

    int choice = keyboard.nextInt();

    if(choice == 1)  {

    if(getMove())  {
    displayBoard(); 

    if(xTurn)
    System.out.println("X Wins!");
    else
    System.out.println("O Wins!");

    System.exit(0);
    }
    else if(boardFull())  {
    displayBoard();

    System.out.println("Draw!");

    System.exit(0);
    }
    else  {
    xTurn = !xTurn;
    }
    }
    else if(choice == 2)
    restart();
    else if(choice == 3)
    System.exit(0);
    else
    System.out.println("Invalid Option");
    }   
    }

    public static void main(String[] args)  {

    TicTacToe game = new TicTacToe();

    game.play();
}