code: @Override
    public final void setHorizontalAlignment(int alignment) {
  	if ((alignment == LEFT) || (alignment == CENTER) || (alignment == RIGHT)) {
  	  this.alignment = alignment;
  	  reajustTextGap();
  	} else {
  	  throw new IllegalArgumentException();
  	}
    }
docs: Sets the horizontal alignment of the text. {@code SplitButton}'s default is
  {@code SwingConstants.CENTER}.
  
  @param alignment
  the alignment value, one of the following values:
  <ul>
  <li>{@code SwingConstants.RIGHT}
  <li>{@code SwingConstants.LEFT}
  <li>{@code SwingConstants.CENTER} (default)
  </ul>
  @throws IllegalArgumentException
  if the alignment is not one of the valid values