rspec/rules/S2864/java/rule.adoc

== Why is this an issue?

`Map` is an object that maps keys to values. A map cannot contain duplicate keys, which means each key can map to at most one value.

When both the key and the value are needed, it is more efficient to iterate the `entrySet()`, which will give access to both instead of
iterating over the `keySet()` and then getting the value.

If the `entrySet()` method is not iterated when both the key and value are needed, it can lead to unnecessary lookups. This is because each
lookup requires two operations: one to retrieve the key and another to retrieve the value. By iterating the `entrySet()` method, the
key-value pair can be retrieved in a single operation, which can improve performance.

=== Noncompliant code example

[source,java,diff-id=1,diff-type=noncompliant]
----
public void doSomethingWithMap(Map<String,Object> map) {
  for (String key : map.keySet()) {  // Noncompliant; for each key the value is retrieved
    Object value = map.get(key);
    // ...
  }
}
----


=== Compliant solution

[source,java,diff-id=1,diff-type=compliant]
----
public void doSomethingWithMap(Map<String,Object> map) {
  for (Map.Entry<String,Object> entry : map.entrySet()) {
    String key = entry.getKey();
    Object value = entry.getValue();
    // ...
  }
}
----

== Resources

=== Documentation

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

=== Articles & blog posts

* https://www.baeldung.com/java-map-entries-methods[Baeldung - Java Map methods]

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

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

=== Message

Iterate over the "entrySet" instead of the "keySet".


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