question: void add ( MembershipKeyImpl key ) { InetAddress group = key . group ( ) ; List < MembershipKeyImpl > keys ; if ( groups == null ) { groups = new HashMap < InetAddress , List < MembershipKeyImpl > > ( ) ; keys = null ; } else { keys = groups . get ( group ) ; } if ( keys == null ) { keys = new LinkedList < MembershipKeyImpl > ( ) ; groups . put ( group , keys ) ; } keys . add ( key ) ; }
target:  Add membership to the registry, returning a new membership key.