import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;

/** Test cases for Rule #6: "Avoid using Optional in fields, method parameters, and collections." */
public class Marks6 {

    // :: warning: (optional.field)
    Optional<String> optionalField = Optional.ofNullable(null);

    // :: warning: (optional.parameter)
    void optionalParameter(Optional<String> arg) {}

    Optional<String> okUses() {
        Optional<String> os = Optional.of("hello world");
        return os;
    }

    void illegalInstantiations() {
        // :: warning: (optional.as.element.type)
        List<Optional<String>> los = new ArrayList<>();
        // :: warning: (optional.as.element.type)
        List<Optional<String>> los2 = new ArrayList<Optional<String>>();
        // :: warning: (optional.as.element.type)
        Set<Optional<String>> sos = new HashSet<>();
    }
}