Java: NumberTile Game

I am doing the infamous Number Tile game program. In which you have a number tile shaped like a diamond. Using an array list you fill out the diamond with any random integer 1-9. You can then place your a numbertile from your hand on to the board if it meets the requirement. I am trying to see what causes my program to crash.

package diamond;

/** * * @author Snake */ import java.util.ArrayList ;

public class TileGame { private ArrayList board;

// Creates an empty board
public TileGame() 
{
    board= new ArrayList() ;
    NumberTile FirstD= new NumberTile();
    board.add(FirstD);
    System.out.println(board);
}

// Accessor for the board
public ArrayList<NumberTile> getBoard() 
{
    // Do not modify this method
    return board ;
}

// Creates and returns a hand of 5 random number tiles
public ArrayList<NumberTile> getHand() 
{
    ArrayList<NumberTile> hand = new ArrayList<NumberTile>() ;
    for(int i=0; i<5; i++)
    {
        NumberTile random = new NumberTile();
        hand.add(random);
    }
    return hand;
}

// If the current tile fits in the board (without rotating) then
// return the index i of a tile in the board so that the current tile 
// fits before ti for i = 0..k-1, or return k if the current tile fits
// after the last tile.   If the tile does not fit, return -1
public int getIndexForFit(NumberTile currentTile) 
{

    if(currentTile.getRight()==board.get(0).getLeft())
    {
           return 0;
    }
    if(currentTile.getLeft()==board.get(board.size()-1).getRight())
    {
        return board.size();
    }
     for(int i=0; i<board.size(); i++)
    {
        if(board.get(i).getLeft()==currentTile.getRight() && 
                board.get(i-1).getRight()==currentTile.getLeft())
        {
            return i;
        }
    }

        return -1 ;


}

// Call the method getIndexForFit to see whether a tile can be inserted
// into the board. In this method the tile can be rotated. If the tile
// can be inserted, return true.  If the tile does not fit after 
// rotating (at most 3 times), return false.
public boolean canInsertTile(NumberTile currentTile) 
{
    for(int i=0; i<=3; i++)
    {
        if(getIndexForFit(currentTile)!=-1)
        {
            return true;
        }
        else 
            currentTile.rotate();

    }
  return false ;
}

// Make a move. I.e. if a tile in the hand fits on the board
// then remove it from the hand and place it in the board. If no tile
// from the hand fits, then add another tile to the hand
public void makeMove(ArrayList<NumberTile> hand) 
{
    NumberTile drawHand = new NumberTile();
    for(int i=0; i<hand.size(); i++)
    {
        if(canInsertTile(hand.get(i))==true)
        {
            int index = getIndexForFit(hand.get(i));
            board.add(index,hand.get(i));
            hand.remove(hand.get(i));
        }

        else if(canInsertTile(hand.get(i))==false && i==hand.size()-1)
        {
            hand.add(drawHand);
        }
    }  

}

/**
* Get the board as a String
* @return the board as a multi-line String
*/
public String toString() 
{
    // Do not modify this method
    return board.toString() ;  // ArrayList as a String
}

} // end of TileGame class