code: void setElement(Object aElement, int column) {
          if (reserved[column]) throw new IllegalArgumentException("setElement - position already taken");
          
          cells[column] = aElement;
          if (aElement != null) {
              reserved[column] = true;
          }
      }
docs: Puts <CODE>Cell</CODE> to the <CODE>Row</CODE> at the position given, doesn't reserve colspan.
  
  @param   aElement    the cell to add.
  @param   column  the position where to add the cell.