rspec/rules/S3824/java/rule.adoc

== Why is this an issue?

It's a common pattern to test the result of a ``++java.util.Map.get()++`` against ``++null++`` or calling ``++java.util.Map.containsKey()++`` before proceeding with adding or changing the value in the map. However the ``++java.util.Map++`` API offers a significantly better alternative in the form of the ``++computeIfPresent()++`` and ``++computeIfAbsent()++`` methods. Using these instead leads to cleaner and more readable code.


*Note* that this rule is automatically disabled when the project's ``++sonar.java.source++`` is not 8.


=== Noncompliant code example

[source,java]
----
V value = map.get(key);
if (value == null) {  // Noncompliant
  value = V.createFor(key);
  if (value != null) {
    map.put(key, value);
  }
}
if (!map.containsKey(key)) {  // Noncompliant
  value = V.createFor(key);
  if (value != null) {
    map.put(key, value);
  }
}
return value;
----


=== Compliant solution

[source,java]
----
return map.computeIfAbsent(key, k -> V.createFor(k));
----


=== Exceptions

This rule will not raise an issue when trying to add ``++null++`` to a map, because ``++computeIfAbsent++`` will not add the entry if the value returned by the function is ``++null++``.

== Resources

=== Related rules

* S6104 - Map "computeIfAbsent()" and "computeIfPresent()" should not be used to add "null" values.


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

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

=== Message

Replace this ("Map.get()" and condition | "Map.containsKey()") with a call to ("Map.computeIfAbsent()" | "Map.computeIfPresent()").


=== Highlighting

Primary: condition

 Secondary: ``++Map.get++`` call or ``++Map.containsKey++`` call


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

=== is related to: S6104

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