private static String keyToFieldName( String key ) {
		int dotIndex = key.indexOf( '.' );
		if( dotIndex < 0 )
			return key;

		// remove first dot in key and change subsequent character to uppercase
		return key.substring( 0, dotIndex )
			+ Character.toUpperCase( key.charAt( dotIndex + 1 ) )
			+ key.substring( dotIndex + 2 );
	}
Applies the given value to an annotated field of the given object.
The field must be annotated with {@link Styleable}.

@param obj the object
@param key the name of the field
@param value the new value
@return the old value of the field
@throws UnknownStyleException if object does not have an annotated field with given name
@throws IllegalArgumentException if value type does not fit to expected type
flatlaf-core/src/main/java/com/formdev/flatlaf/ui/FlatStylingSupport.java