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:

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

public class MyClass {
    int enum = 42;            // Noncompliant
    String _ = "";            // Noncompliant
}

Compliant solution

public class MyClass {
    int magic = 42;           // Noncompliant
    String s = "";            // Noncompliant
}

Resources

Documentation