rspec/rules/S2165/java/rule.adoc

This rule raises an issue when a finalizer assign `null` to fields of the instance it is called on.

== Why is this an issue?

In the Java object lifecycle, the `finalize` method for an instance is called
after the garbage collector has determined that the instance can be removed from the object heap.
Therefore, it is unnecessary to implement a finalizer to set instance fields explicitly to `null`
to tell the garbage collector that the instance no longer needs them.

In the worst case, implementing `finalize` is even counterproductive because it might accidentally create new references
from other (living) objects on the heap to the collectible instance, thus, reviving it.

**Important note about finalizers:**

There are no guarantees when the Java Runtime will call the `finalize` method or whether it will be called at all.

Using finalizers is, therefore, a bad practice. They should never be used to free resources,
such as closing streams, freeing locks, or freeing native system resources.
Consider other freeing mechanisms instead, such as an explicit `close`, `unlock`, or `free` method in your class.

== How to fix it

Remove assignments from your finalizer that assign `null` to fields of the instance the finalizer is called on.
When this leaves you with an empty finalizer body, remove the finalizer.

=== Code examples

==== Noncompliant code example

[source,java,diff-id=1,diff-type=noncompliant]
----
public class Foo {
  private String name;

  @Override
  void finalize() {
    name = null;  // Noncompliant, instance will be removed anyway
  }
}
----

==== Compliant solution

[source,java,diff-id=1,diff-type=compliant]
----
public class Foo { // Compliant
  private String name;
}
----

== Resources

=== Documentation

* https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#finalize--[Java SE 8 API Specification - Object.finalize]

=== Articles & blog posts

* https://howtodoinjava.com/java/basics/why-not-to-use-finalize-method-in-java[Java finalize() – Why We Should Not Use It? - Lokesh Gupta]
* https://www.baeldung.com/java-finalize[A Guide to the finalize Method in Java - Baeldung]

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

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

=== Message

Remove this nullification of "xxx".


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