Lesson 20: Optional & Avoiding NullPointerException

Optional makes 'this might not have a value' explicit in the type system, forcing callers to handle the absence instead of risking an NPE.

Real-time example

A user-lookup service returns Optional<User> so callers can't forget to handle 'user not found' — the compiler nudges them.

Optional<User> findUser(String id) {
    return id.equals("u1") ? Optional.of(new User("Amit")) : Optional.empty();
}
findUser("u2")
    .map(u -> u.name)
    .ifPresentOrElse(
        name -> System.out.println("Found: " + name),
        () -> System.out.println("No such user")
    );

What's happening

ifPresentOrElse forces you to handle both branches at the call site instead of silently returning null and crashing later.

Never call .get() on an Optional without checking isPresent() first — that defeats the entire point.