public void setTabUnderlinePlacement( int placement ) {
		putClientProperty( TAB_BUTTON_UNDERLINE_PLACEMENT, (placement >= 0) ? placement : null );
	}
Specifies placement of underline if toggle button type is {@link ButtonType#tab}.

@param placement  One of the following constants defined in SwingConstants:
                  {@link #TOP}, {@link #LEFT}, {@link #BOTTOM}, or {@link #RIGHT}.
@since 2.3
flatlaf-extras/src/main/java/com/formdev/flatlaf/extras/components/FlatToggleButton.java