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🏷 Optional 4 patterns

Topic: Optional

All Java patterns related to Optional — java.evolved

Optional.ifPresentOrElse()

Old Optional<User> user = findUser(id); if (user.isPresent()) { greet(user.get()); } else { handleMissing(); }

Modern findUser(id).ifPresentOrElse( this::greet, this::handleMissing );

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JDK 9+ learn more →

Optional.or() fallback

Old Optional<Config> cfg = primary(); if (!cfg.isPresent()) { cfg = secondary(); } if (!cfg.isPresent()) { cfg = defaults(); }

Modern Optional<Config> cfg = primary() .or(this::secondary) .or(this::defaults);

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JDK 9+ learn more →

Optional chaining

Old String city = null; if (user != null) { Address addr = user.getAddress(); if (addr != null) { city = addr.getCity(); } } if (city == null) city = "Unknown";

Modern String city = Optional.ofNullable(user) .map(User::address) .map(Address::city) .orElse("Unknown");

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JDK 9+ learn more →

Optional.orElseThrow() without supplier

Old // Risky: get() throws if empty, no clear intent String value = optional.get(); // Verbose: supplier just for NoSuchElementException String value = optional .orElseThrow(NoSuchElementException::new);

Modern // Clear intent: throws NoSuchElementException if empty String value = optional.orElseThrow();

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JDK 10+ learn more →