== Why is this an issue?

Programming languages evolve over time, and new versions of Java introduce additional keywords.
If future keywords are used in the current code, it can create compatibility issues when transitioning to newer versions of Java.
The code may fail to compile or behave unexpectedly due to conflicts with newly introduced keywords.

The following keywords are marked as invalid identifiers:

[frame=all]
[cols="^1,^1"]
|===
|Keyword|Added in version

|`_`|9
|`enum`|5.0
|===

`assert` and `strictfp` are another example of valid identifiers which became keywords in later versions, but are not supported by this rule.

== How to fix it

Rename the identifiers that use Java keywords.

=== Code examples

==== Noncompliant code example

[source,java,diff-id=1,diff-type=noncompliant]
----
public class MyClass {
    int enum = 42;            // Noncompliant
    String _ = "";            // Noncompliant
}
----


==== Compliant solution

[source,java,diff-id=1,diff-type=compliant]
----
public class MyClass {
    int magic = 42;           // Noncompliant
    String s = "";            // Noncompliant
}
----

== Resources
=== Documentation
* https://docs.oracle.com/javase/tutorial/java/nutsandbolts/_keywords.html[Oracle - Java Language Keywords]

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

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

=== Message

Rename this variable to something other than "XXX", which is a Java keyword.


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

=== is duplicated by: S3859

=== relates to: S1669

=== relates to: S2306

=== is related to: S1527

=== is related to: S1189

=== on 8 Aug 2013, 16:32:59 Freddy Mallet wrote:
Is implemented by \http://jira.codehaus.org/browse/SONARJAVA-280

=== on 13 Aug 2019, 10:18:47 Michael Gumowski wrote:
Removing reference to JIRA ticket in rule description. See SONARJAVA-285 and SONARJAVA-3179 for rule limitation.

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