final Object firstElement = list.stream()
.findFirst()
.orElse(new Object()) //Give a default value if there are no elements
final Object firstElement = list.stream()
.findFirst()
.orElseThrow(() -> new Exception()) //Throw an exception if there are no elements
list.get(0);
set.iterator().next();
!list_or_set.isEmpty()
public Node<T> getFirst()