default String getStyleClass() {
		return (String) getClientProperty( FlatClientProperties.STYLE_CLASS );
	}
Returns the style class(es) of a component (separated by space characters)
or {@code null} if no style class has been assigned.

@see FlatClientProperties#STYLE_CLASS
flatlaf-extras/src/main/java/com/formdev/flatlaf/extras/components/FlatStyleableComponent.java