`List.of(...)`: what kind of list does it create and a common gotcha?

Answer

`List.of(...)` creates an unmodifiable (immutable) list. If you try to add/remove elements, you get `UnsupportedOperationException`. A common gotcha: it also does not allow null elements (it throws `NullPointerException` on creation).

List<String> xs = List.of("a", "b");
// xs.add("c"); // throws UnsupportedOperationException