import java.util.Collection; import java.util.LinkedHashSet; import java.util.List; class A { <T> void bar(List<T> root, LinkedHashSet<List<T>> list) { add<caret>IfNotNull(root, list); } private static <T> void addIfNotNull(T element, Collection<T> result) { nested(result, element); } private static <S> void nested(Collection<S> result, S element) {} }