[java] UseLocaleWithCaseConversions - false positive with a non-String class

[winhkey]

Affects PMD Version: 6.53.0

Rule: UseLocaleWithCaseConversions

Description: The class Ulid has a toLowerCase() method, but no overloads take a locale. The class Ulid is not a string.

Code Sample demonstrating the issue:

public class Foo {
    public static String generateUlid(boolean uppercase) {
        Ulid ulid = Ulid.fast();
        return uppercase ? ulid.toString() : ulid.toLowerCase(); // here problem
    }
}

Expected outcome:

PMD reports a violation "UseLocaleWithCaseConversions: When doing a String.toLowerCase()/toUpperCase() call, use a Locale" at line 4, but that's wrong. That's a false positive.

Running PMD through: CLI

Additional info:

• Ulid comes from https://github.com/f4b6a3/ulid-creator
• Maven coordinates:

        <dependency>
            <groupId>com.github.f4b6a3</groupId>
            <artifactId>ulid-creator</artifactId>
            <version>5.1.0</version>
        </dependency>

• The source for the class Ulid: https://github.com/f4b6a3/ulid-creator/blob/dc0082bad6bc7d43f9a416971886f146ad26a4e2/src/main/java/com/github/f4b6a3/ulid/Ulid.java#L437

[jsotuyod]

This is no longer reproducible under PMD 7.0.0