How can I expand things from a superclass? (Java)
<p>I want to expand the method <code>setValueAt(int row, int col, int value)</code> from the superclass <code>NumberBoard</code> in my subclass <code>Sudoku</code>.</p>

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

<p>The superclass <code>NumberBoard</code> (I can't change the superclass):</p>

<pre><code>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 &gt;= 0} or {@link #EMPTY}.
 */
public void setValueAt(int row, int col, int value) {
    if (isInRange(row, col) &amp;&amp; (value == EMPTY || value &gt;= 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}
 *         Â otherwise.
 */
protected final boolean isInRange(int row, int col) {
    return 0 &lt;= row
            &amp;&amp; row &lt; board.length
            &amp;&amp; 0 &lt;= col
            &amp;&amp; col &lt; board[row].length;
  }
}
</code></pre>

<p>And my Code for my subclass <code>Sudoku</code> (Unfortunately without a point) :</p>

<pre><code>public class Sudoku extends NumberBoard {


public void setValueAt(int row, int col, int value) {
    super.setValueAt(row, col, value);      
    }
  }
</code></pre>