Reports objects which are a subtype of
java.util.Set or java.util.Map
and which may contain java.net.URL objects. Adding java.net.URL
objects to such collections can cause performance problems because of calls to the
equals() and hashCode()
methods of java.net.URL.
java.net.URL's equals() and hashCode() method use a DNS
lookup, which depending on the availability of the network and the speed of the DNS server
can cause significant delays.