== Why is this an issue?

The `equals` and `hashCode` methods of `java.net.URL` may trigger a name service lookup (typically DNS) to resolve the hostname or IP
address. Depending on the configuration, and network status, this lookup can be time-consuming.

On the other hand, the `URI` class does not perform such lookups and is a better choice unless you specifically require the functionality
provided by `URL`.

In general, it is better to use the `URI` class until access to the resource is actually needed, at which point you can 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.
It suggests reconsidering the use of `URL` in such scenarios to avoid potential performance issues related to name service lookups.

== How to fix it
Use the `URI` class until access to the resource is actually needed.

=== Code examples

==== Noncompliant code example

[source,java,diff-id=1,diff-type=noncompliant]
----
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

[source,java,diff-id=1,diff-type=compliant]
----
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
    // ...
  }
}
----

== Resources

* https://docs.oracle.com/en/java/javase/20/docs/api/java.base/java/net/URL.html[Oracle Java SE - java.net.URL]


ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Use the URI class instead.


'''
== Comments And Links
(visible only on this page)

=== on 8 Oct 2014, 07:17:12 Nicolas Peru wrote:
\[~freddy.mallet] This one will probably require to have Generics in the symbol table.

endif::env-github,rspecator-view[]