/var/tmp $ javac UnusedVarTest.java

/var/tmp $ cat config.xml
<?xml version="1.0"?>
<!DOCTYPE module PUBLIC
    "-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
    "https://checkstyle.org/dtds/configuration_1_3.dtd">

<module name="Checker">
    <module name="TreeWalker">
        <module name="UnusedLocalVariable"/>
    </module>
</module>

/var/tmp $ cat UnusedVarTest.java

public class UnusedVarTest
{
    public void testParameters()
    {
        String[] tests = { "one", "two" };

        int i = 0;
        for (String test : tests)
        {
            switch (i++)
            {
                default:
                case 0:
                    System.out.println("one: " + test);
                    break;
                case 1:
                    System.out.println("two: " + test);
                    break;
            }
        }
    }
}

/var/tmp $ RUN_LOCALE="-Duser.language=en -Duser.country=US"
/var/tmp $ java $RUN_LOCALE -jar checkstyle-10.13.0-all.jar -c config.xml UnusedVarTest.java
Starting audit...
[ERROR] /home/grodriguez/work/hc/UnusedVarTest.java:8:9: Unused local variable 'i'. [UnusedLocalVariable]
Audit done.
Checkstyle ends with 1 errors.