== Why is this an issue?

include::../description.adoc[]

[source,java]
----
public class MyClass {
  private int foo = 42; // Noncompliant: foo is unused and should be removed

  public int compute(int a) {
    return a * 42;
  }

}
----

Note that this rule does not take reflection into account, which means that issues will be raised on ``++private++`` fields that are only accessed using the reflection API.

=== Exceptions

The rule admits 3 exceptions:

* Serialization ID fields

The Java serialization runtime associates with each serializable class a version number called `serialVersionUID`, which is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible for serialization.

A serializable class can declare its own `serialVersionUID` explicitly by declaring a field named `serialVersionUID` that must be static, final, and of type long. By definition, those `serialVersionUID` fields should not be reported by this rule:


[source,java]
----
public class MyClass implements java.io.Serializable {
  private static final long serialVersionUID = 42L;  // Compliant by exception
}
----

* Annotated fields and classes annotated with Lombok annotations

The unused field in this class will not be reported by the rule as it is annotated,
except if annotation class `SomeAnnotation` is listed in the `ignoreAnnotations` parameter (see Parameters).
[source,java]
----
public class MyClass {
  @SomeAnnotation
  private int unused;  // Compliant by exception
}
----

* Fields from classes with native methods

The unused field in this class will not be reported by the rule as it might be used by native code.
[source,java]
----
public class MyClass {
  private int unused = 42;  // Compliant by exception
  private native static void doSomethingNative();
}
----

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

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

=== Parameters

.ignoreAnnotations
****

----
""
----

A comma separated list of fully qualified annotation class names that do not prevent a private field from being reported.
****

include::../message.adoc[]

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

include::../comments-and-links.adoc[]

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