I know what is the purpose and how to handle Stream as a query output, i.e.:
Stream<Person> findAll();
However, recently I stumbled upon org.springframework.data.util.Streamable<T>, used in the same way as a Stream:
Streamable<Person> findByNameContaining(String name, Sort sort);
What is the use case of Streamable?
interface Streamable
Functional Interface: This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
Stream from java.util is just an interface.
Streamable was created from Spring as a functional interface that extended Iterable<T>
Streamable also has some default methods and some static ones. But it was used to be able to provide an Iterator as a lambda function taking advantage of how functional interfaces work.
That's only technical info.
Practical now from what I understand it's main use is to convert an Iterable<T> into a Stream<T>
Iterable<String> it = Arrays.asList("a","b","c");
Stream<String> s = Streamable.of(it).stream();
It didn't exist an easy way to directly convert an Iterable<T> into a Stream<T> therefore they invented it.
You can find most of those uses here Uses of Spring Streamable