rowHeader = (JViewport) component;
rowHead = (JViewport) component;
  public void addLayoutComponent(String key, Component component)   {    if (key == VIEWPORT)      viewport = (JViewport) component;    else if (key == VERTICAL_SCROLLBAR)      verticalScrollBar = (JScrollBar) component;    else if (key == HORIZONTAL_SCROLLBAR)      horizontalScrollBar = (JScrollBar) component;    else if (key == ROW_HEADER)      rowHeader = (JViewport) component;    else if (key == COLUMN_HEADER)      columnHeader = (JViewport) component;    else if (key == LOWER_RIGHT_CORNER)      lowerRight = component;    else if (key == UPPER_RIGHT_CORNER)      upperRight = component;    else if (key == LOWER_LEFT_CORNER)      lowerLeft = component;    else if (key == UPPER_LEFT_CORNER)      upperLeft = component;  }