question: public static Map appendElementToMap ( String key , Set values , Map toMap ) { if ( ( key != null ) && ( values != null ) && ( ! values . isEmpty ( ) ) && ( toMap != null ) ) { Set previousValues = ( Set ) toMap . get ( key ) ; if ( ( previousValues != null ) && ( ! previousValues . isEmpty ( ) ) ) { previousValues . addAll ( values ) ; } else { toMap . put ( key , values ) ; } } return toMap ; }
target:  Appends a key/value pair to a map