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Optional<T> is Java's wrapper for "value or absent" — alternative to returning null. Forces callers to handle the empty case.

Creation:

Optional<String> some = Optional.of("hello");          // throws if null
Optional<String> empty = Optional.empty();
Optional<String> nullable = Optional.ofNullable(maybeNull);

Consumption:

Optional<User> u = findById(id);

// most common patterns:
String name = u.map(User::getName).orElse("unknown");
u.ifPresent(user -> log(user));
User user = u.orElseThrow(() -> new NotFoundException(id));

// chaining:
int nameLength = findById(id)
    .map(User::getName)
    .map(String::length)
    .orElse(0);

Anti-patterns to avoid:

• if (opt.isPresent()) opt.get() — use ifPresent or orElse
• Optional as a field type — use null (or annotations); Optional is for return values
• Optional as a method parameter — overload with/without instead

Optional is well-suited for return types of methods that may not have a value (DB lookups, parses).