Java 8 Optional orElse orElseThrow inconsistent [duplicate]

Question

If a is Optional[123] and b is Optional[empty].

a.orElse(b.orElseThrow(() -> new UnexpectedInternalException(
                    "Error")))

Why does it throw?

Answer 1

orElse() is a method, and before that method is executed, its arguments are evaluated. In this case the evaluation of the argument (b.orElseThrow(() -> new UnexpectedInternalException("Error"))) throws an exception.

Answer 2

Because parameters are evaluated first. This has nothing to do with Optional...