public boolean gameOver()
    {
       JFrame frame = new JFrame("Game Over");
       boolean gameIsOver = false;
       int filledSquares = 0;
       int emptySquares = 0; // doesn't affect anything
       int playerOneScore = players.get(Constants.PLAYER_ONE).getScore();
       int playerTwoScore = players.get(Constants.PLAYER_TWO).getScore();

       //this checks the board to see if all of the squares are populated
       for(int row = 0; row < Constants.ROWS; row++)
       {
            for(int col = 0; col <Constants.COLUMNS; col++)
            {
                if (board[row][col].getDiscColor() != Constants.EMPTY)
                    filledSquares++;
                else if(board[row][col].getDiscColor() == Constants.EMPTY)
                    emptySquares++;
            }
       }

       if (filledSquares == Constants.MAX_DISCS)
       {
           if (playerOneScore > playerTwoScore )
           {
               JOptionPane.showMessageDialog(frame, "Game Over! Player One wins!");
               //System.exit(0);
           }
           else if (playerTwoScore > playerOneScore)
           {
               JOptionPane.showMessageDialog(frame, "Game Over! Player Two wins!");
               //System.exit(0);
           }
           else
           {
               JOptionPane.showMessageDialog(frame, "Game Over! It is a tie!");
               //System.exit(0);
           }


       }

       //checks to see if neither player can make a valid move.

       boolean anyValidMoves = false;
       Color color;


       for(int row = 0; row < Constants.ROWS; row++)
       {
            for(int col = 0; col <Constants.COLUMNS; col++)

            {
                color = players.get(Constants.PLAYER_ONE).getDiscColor();
                if(checkUpValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkUpLeftValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkLeftValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkLeftDownValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkDownValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkDownRightValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkRightValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkUpRightValid(row, col, color))
                {
                   anyValidMoves = true;
                }
            }
        }

       if (anyValidMoves == false)
       {
           if (playerOneScore > playerTwoScore )
           {
               JOptionPane.showMessageDialog(frame, "No available moves! Game Over! Player One wins!");
               //System.exit(0);
           }
           else if (playerTwoScore > playerOneScore)
           {
               JOptionPane.showMessageDialog(frame, "No available moves! Game Over! Player Two wins!");
               //System.exit(0);
           }
           else
           {
               JOptionPane.showMessageDialog(frame, "Now available moves! Game Over! It is a tie!");
               //System.exit(0);
           }

       }


       for(int row = 0; row < Constants.ROWS; row++)
       {
            for(int col = 0; col <Constants.COLUMNS; col++)
            {
                color = players.get(Constants.PLAYER_TWO).getDiscColor();

                if(checkUpValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkUpLeftValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkLeftValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkLeftDownValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkDownValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkDownRightValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkRightValid(row, col, color))
                {
                   anyValidMoves = true;
                }
                if(checkUpRightValid(row, col, color))
                {
                   anyValidMoves = true;
                }
            }
        }
       if (anyValidMoves == false)
       {
           if (players.get(Constants.PLAYER_ONE).getScore() > players.get(Constants.PLAYER_TWO).getScore() )
           {
               JOptionPane.showMessageDialog(frame, "Game Over! Player One wins!");
               return gameIsOver;
           }
           else if (players.get(Constants.PLAYER_TWO).getScore() > players.get(Constants.PLAYER_ONE).getScore())
           {
               JOptionPane.showMessageDialog(frame, "Game Over! Player Two wins!");
               return gameIsOver;
           }
           else
           {
               JOptionPane.showMessageDialog(frame, "Game Over! It is a tie!");
               return gameIsOver;
           }


       }

    return gameIsOver;
    }