code: public void setLayout(String layout)
      {
          if (layout == null)
          {
              String message = Logging.getMessage("nullValue.StringIsNull");
              Logging.logger().severe(message);
              throw new IllegalArgumentException(message);
          }
          if (!this.layout.equals(layout))
          {
              this.layout = layout;
              clearControls();
          }
      }
docs: Sets the desired layout. Can be one of {@link AVKey#HORIZONTAL} or {@link AVKey#VERTICAL}.
  
  @param layout the desired layout.