The equals
and hashCode
methods of java.net.URL
both may trigger a name service (usually DNS) lookup to
resolve the host name or IP address. Depending on the configuration, and network status, that can take a long time. URI
on the other hand
makes no such calls and should be used instead unless the specific URL
functionality is required.
In general it is better to use the URI
class until access to the resource is actually needed, at which point you can just convert the
URI
to a URL
using URI.toURL()
.
This rule checks for uses of URL
's in Map
and Set
, and for explicit calls to the equals
and
hashCode
methods.
public void checkUrl(URL url) { Set<URL> sites = new HashSet<URL>(); // Noncompliant URL homepage = new URL("http://sonarsource.com"); // Compliant if (homepage.equals(url)) { // Noncompliant // ... } }
public void checkUrl(URL url) { Set<URI> sites = new HashSet<URI>(); // Compliant URI homepage = new URI("http://sonarsource.com"); // Compliant URI uri = url.toURI(); if (homepage.equals(uri)) { // Compliant // ... } }