Bingo cover() method not working. Help!

[08cmoss]

I have written all the code for my Bingo game to work, but my cover() method in BingoCard is not working. I have gotten rid of the null pointer exception when comparing the two strings. But regardless the cover() method will not work. I have attached the BingoCard.java code below and below that is the BingoGame.java code to make the whole thing work.
The cover() method is supposed to replace the BingoSquare with a null, which will then be changed to "****" in the toString() method. I think I have all the code correct, but the cover() method is not covering any of the squares of myBingoCard with null. Help?

public class BingoCard
{
  private BingoSquare[][] myCard;
  
//hard coding numbers into each row and column 
  public BingoCard()
  { 
    myCard = new BingoSquare[5][5];
    myCard[0][0] = new BingoSquare(3);
    myCard[0][1] = new BingoSquare(18);
    myCard[0][2] = new BingoSquare(33);
    myCard[0][3] = new BingoSquare(48);
    myCard[0][4] = new BingoSquare(63);
    
    myCard[1][0] = new BingoSquare(6);
    myCard[1][1] = new BingoSquare(21);
    myCard[1][2] = new BingoSquare(36);
    myCard[1][3] = new BingoSquare(51);
    myCard[1][4] = new BingoSquare(66);
    
    myCard[2][0] = new BingoSquare(9);
    myCard[2][1] = new BingoSquare(24);
    //myCard[2][2] = null;  moved down to toString()
    myCard[2][3] = new BingoSquare(54);
    myCard[2][4] = new BingoSquare(69);
    
    myCard[3][0] = new BingoSquare(12);
    myCard[3][1] = new BingoSquare(27);
    myCard[3][2] = new BingoSquare(42);
    myCard[3][3] = new BingoSquare(57);
    myCard[3][4] = new BingoSquare(72);
    
    myCard[4][0] = new BingoSquare(15);
    myCard[4][1] = new BingoSquare(30);
    myCard[4][2] = new BingoSquare(45);
    myCard[4][3] = new BingoSquare(60);
    myCard[4][4] = new BingoSquare(75);
    
  }
  public String toString()
  {
   myCard[2][2] = null;
   String a = ""; 
   for(int j = 0; j < 5; j++)
   {
     for(int i = 0; i < 5; i++)
     {
       //add a space somewhere in here below.
       if(myCard[j][i] != null){
       a += myCard[j][i] + " ";
       }
       else a += "**** ";
       }
     a += "\n";
   }
   return a;
  }
   public boolean cover(BingoBall ball){
    for(int row = 0; row < 5; row++){
      for(int col = 0; col < myCard[row].length; col++)
{
  if(myCard[row][col] != null && myCard[row][col].equals(ball.toString()))
  {
    myCard[row][col] = null;
      return true;
    }
   }
  }
    return false;
}
  public boolean hasBingo(){
   //four for loop for rows, columns, and two diagonals 
    for(int row = 0; row < myCard.length; row++){
      for(int col = 0; col < myCard[row].length; col++){
        if(myCard[row][col] == null){
         return true; 
        }
      }
     }
    return false;
  }
}

************************************************** *********************

BingoGame.java code:

//********************************************************************
//  
//
//  
//  Driver to test cover method in BingoCard class
//********************************************************************

public class BingoGame
{
  /******************************************************************
    Creates myBingoCard as a 5 x 5 array of BingoBalls
    Creates 5 specific BingoBalls and covers myBingocard
    Prints "Bingo" on a true return from cover method
    Prints final state of myBingoCard
  *******************************************************************/
  public static void main (String[] args)
  {
    // create my Bingo Card
    BingoCard myBingoCard = new BingoCard();

    // create some Bingo Balls, cover on myBingoCard, and check for Bingo
    // change BingoBall values to test numbers on and not on your card
    // test at least one Bingo on a row, a column, or a diagonal
    if (myBingoCard.cover(new BingoBall(1)) && myBingoCard.hasBingo())  // not on myBingoCard
      System.out.println("Bingo on 1st");    
    if (myBingoCard.cover(new BingoBall(3)) && myBingoCard.hasBingo())  // next four are a diagonal
      System.out.println("Bingo on 2nd");
    if (myBingoCard.cover(new BingoBall(21)) && myBingoCard.hasBingo())
      System.out.println("Bingo on 3rd");
    if (myBingoCard.cover(new BingoBall(57)) && myBingoCard.hasBingo())
      System.out.println("Bingo on 4th");
    if (myBingoCard.cover(new BingoBall(75)) && myBingoCard.hasBingo())
      System.out.println("Bingo on 5th");
    
    // print the final state of myBingoCard
    System.out.println(myBingoCard);
  }
}

[Norm]

my cover() method in BingoCard is not working.

Please explain what "not working" means. The code has no comments describing what it is supposed to do.

Please edit your post and wrap the code in code tags. See: BB Code List - Java Programming Forum