How can I expand things from a superclass? (Java)

I want to expand the method setValueAt(int row, int col, int value) from the superclass NumberBoard in my subclass Sudoku.

In Sudoku the value is empty or 1 to 9, but in the superclass NumberBoard the value may be empty or >= 0. How can I change it in my subclass Sudoku?

The superclass NumberBoard (I can't change the superclass):

public class NumberBoard {

/** Value of an empty cell. */
public static final int EMPTY = -1;

/** The board's state. */
private int[][] board;

/**
 * Sets the value of the given cell.
 * 
 * @param row
 *            the cell's row, starting at 0.
 * @param col
 *            the cell's column, starting at 0.
 * @param value
 *            the cell's value. Must be {@code >= 0} or {@link #EMPTY}.
 */
public void setValueAt(int row, int col, int value) {
    if (isInRange(row, col) && (value == EMPTY || value >= 0)) {
        board[row][col] = value;
    }
}


/**
 * Checks if the given coordinates identify a valid cell on the board.
 * 
 * @param row
 *            the cell's row, starting at 0.
 * @param col
 *            the cell's column, starting at 0.
 * @return {@code true} if the coordinate is in range, {@code false}
 *          otherwise.
 */
protected final boolean isInRange(int row, int col) {
    return 0 <= row
            && row < board.length
            && 0 <= col
            && col < board[row].length;
  }
}

And my Code for my subclass Sudoku (Unfortunately without a point) :

public class Sudoku extends NumberBoard {


public void setValueAt(int row, int col, int value) {
    super.setValueAt(row, col, value);      
    }
  }

In Sudoku the value is empty or 1 to 9, but in the superclass NumberBoard the value may be empty or >= 0. How can I change it in my subclass Sudoku?

You could create your own exception to handle the error case :

public class IncorectValueException extends Exception{
  public IncorectValueException(){
    super();
  }
}

Besides, in NumberBoard class, in setValueAt() method you perform too many unitary processings which should be grouped in a specific method if you want to redefine the behavior of checking valid data according to the class :

`isInRange(row, col) && (value == EMPTY || value >= 0)`

could be a new method : isAcceptableValue(int row, int col, int value)

Change it :

public void setValueAt(int row, int col, int value) throws IncorectValueException{
    if (isInRange(row, col) && (value == EMPTY || value >= 0)) {
        board[row][col] = value;
    }
}

to :

public void setValueAt(int row, int col, int value) throws IncorectValueException{
    if (!isAcceptableValue(row, col)) {
       throw new IncorectValueException();             
    }
      board[row][col] = value;
}

public boolean isAcceptableValue(int row, int col, int value){
   if(isInRange(row, col) && (value == EMPTY || value >= 0)){
     return true;
   }
   return false;
}

Now, the Sudoku class could be like that :

public class Sudoku extends NumberBoard {
     ...
public boolean isAcceptableValue(int row, int col, int value){ 
   if(isInRange(row, col) && (value==EMPTY || (value >= 1 && value <= 9))) {
      return true;             
    }       
    return false;
}