stream

A Java Stream represents a "stream¹" of elements coming from some "source."

You can stream the elements of a List or Set by using the .stream() instance method on each.

Stream<String> heroes = List.of(
    "Deku", 
    "Explosive Hero: Great Explosion Murder God Dynamight",
    "Froppy"
).stream();

Stream<String> villains = Set.of(
    "All for One",
    "Muscular"
).stream();

For arrays there is a static method on Arrays which can stream their contents. You could also first convert the array to a collection with Arrays.asList.

Stream<String> heroes = Arrays.stream(new String[] {
    "Lin Ling", 
    "Lucky Cyan"
});

Stream<String> villains = Arrays.asList(new String[] {
    "E-Soul"
}).stream();

If you legitimately do not have a source collection you can also create a stream directly with Stream.of.

Stream<Character> letterStream = Stream.of('a', 'b', 'c');