74 lines
2.3 KiB
Plaintext
74 lines
2.3 KiB
Plaintext
This rule raises an issue when a finalizer assign `null` to fields of the instance it is called on.
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== Why is this an issue?
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In the Java object lifecycle, the `finalize` method for an instance is called
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after the garbage collector has determined that the instance can be removed from the object heap.
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Therefore, it is unnecessary to implement a finalizer to set instance fields explicitly to `null`
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to tell the garbage collector that the instance no longer needs them.
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In the worst case, implementing `finalize` is even counterproductive because it might accidentally create new references
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from other (living) objects on the heap to the collectible instance, thus, reviving it.
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**Important note about finalizers:**
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There are no guarantees when the Java Runtime will call the `finalize` method or whether it will be called at all.
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Using finalizers is, therefore, a bad practice. They should never be used to free resources,
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such as closing streams, freeing locks, or freeing native system resources.
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Consider other freeing mechanisms instead, such as an explicit `close`, `unlock`, or `free` method in your class.
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== How to fix it
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Remove assignments from your finalizer that assign `null` to fields of the instance the finalizer is called on.
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When this leaves you with an empty finalizer body, remove the finalizer.
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=== Code examples
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==== Noncompliant code example
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[source,java,diff-id=1,diff-type=noncompliant]
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----
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public class Foo {
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private String name;
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@Override
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void finalize() {
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name = null; // Noncompliant, instance will be removed anyway
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}
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}
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----
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==== Compliant solution
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[source,java,diff-id=1,diff-type=compliant]
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----
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public class Foo { // Compliant
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private String name;
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}
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----
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== Resources
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=== Documentation
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* https://docs.oracle.com/javase/8/docs/api/java/lang/Object.html#finalize--[Java SE 8 API Specification - Object.finalize]
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=== Articles & blog posts
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* https://howtodoinjava.com/java/basics/why-not-to-use-finalize-method-in-java[Java finalize() – Why We Should Not Use It? - Lokesh Gupta]
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* https://www.baeldung.com/java-finalize[A Guide to the finalize Method in Java - Baeldung]
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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Remove this nullification of "xxx".
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endif::env-github,rspecator-view[]
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