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.

Noncompliant Code Example

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
    // ...
  }
}

Compliant Solution

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
    // ...
  }
}