Optional

Optional<T> makes absence explicit for return values. It must never contain null and is usually inappropriate for fields, method parameters, collections, or serialization models.

Compose absence

String label = repository.find(id)
    .map(User::displayName)
    .filter(name -> !name.isBlank())
    .orElseGet(() -> "Unknown " + id);

Use map, flatMap, filter, ifPresent, or, and lazy orElseGet. orElse evaluates its fallback eagerly. Avoid unguarded get; use orElseThrow when absence violates the caller’s contract. An empty collection already represents no elements, so do not wrap it in Optional.