Reports java.util.Set and java.util.Map variables that contain java.net.URL objects. Such collections will call the equals() and hashCode() methods on inserted objects, which can cause performance problems on URL objects.

URL's equals() and hashCode() methods can perform a DNS lookup to resolve the host name. This may cause significant delays, depending on the availability and speed of the network and the DNS server. Using java.net.URI instead of java.net.URL will avoid the DNS lookup.

Example:


  Set<URL> set = new HashSet<URL>();