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java8-patterns
The document discusses various design patterns and features introduced in Java 8, emphasizing lambda expressions, the decorator pattern, and monads. It highlights the evolution of programming idioms and the introduction of functional reactive programming as a blend of multi-patterns and paradigms. The summary encapsulates the advancement in coding practices and functionalities available in Java post-version 8.
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java8-patterns
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- 2. #JCConf Agenda • Fluent Decorator •In, Out, In, Out, Shake It All About • The Lonely Override • Monad • Functional Reactive? 2
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- 4. #JCConf Comparator • Building aComparator before Java 8 • Java 8 Wait! you’re cheating!! It‘s not the reverse order. 4
- 5. #JCConf • Use Comparator.reverseOrder •Use Comparator.comparing • High order function Anonymous inner classes were designed to make it easier for Java programmers to pass around code as data. 5
- 6. #JCConf • Order nullsbefore non-null elements. • Decorator Pattern 6
- 7. #JCConf • Can youfigure out this? Refactor it to nullsFirst(byStringLength())？ 7
- 8. #JCConf • This wouldbe better! • last name, and then first name, zip code … 8
- 9. #JCConf • Refactor theDecorator pattern itself 9
- 10. #JCConf In, Out, In,Out, Shake It All About《Java 8 Lambdas》 10
- 11. #JCConf Logger • Invoke isLoggableonly to check whether calling a method on the Logger • it uses information from the rental, but does not use information from the customer • the method is on the wrong object 11
- 12. #JCConf Logger • Invoke isLoggableonly to check whether calling a method on the Logger • it uses information from Logger, but only to push a value into it • the block is on the wrong object 12
- 13. #JCConf Map • it usesinformation from the Map, but only to push a value into it. • the block is on the wrong object. • computeIfPresent、compute、merge … 13
- 14. #JCConf The Lonely Override《Java8 Lambdas》 14
- 15. #JCConf ThreadLocal • Subclass solelyto override a single method • What you really want is providing a block of code to the method! 15
- 16. #JCConf • This wasn'tan antipattern before Java 8—it was the idiomatic way of writing this code • Source code of withInitial 16
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- 18. #JCConf Optional • Null sucks,right? • Optional is trendy now! Optional<Order> WET 18
- 19. #JCConf • Behavioral WET（WriteEverything Twice） – You create Optional<T> – invoke isPresent of Optional<T> – if true, get and map T to Optional<U> – if false, return Optional.empty() • You uses information from Optional<T>, but only to get a Optional<U> from it • In, Out, In, Out, Shake It All About 19
- 20. #JCConf • Let's flatMaprepeatedly. • Using method reference is much clearer. • Monad? Why is it important? – Enable me to talk about monad right now!! 20
- 21. #JCConf • Seriously, amonad is a pattern – You create M<T> – do actions on M<T> – get and map T value(s) to M<U> – do actions on M<U> or else • Optional Monad – You create Optional<T> – invoke isPresent of Optional<T> – if true, get and map T to Optional<U> – if false, return Optional.empty() 21
- 22. #JCConf • Seriously, amonad is a pattern – You create M<T> – do actions on M<T> – get and map T value(s) to M<U> – do actions on M<U> or else • Optional Monad – You create Optional<T> – invoke isPresent of Optional<T> – if true, get and map T to Optional<U> – if false, return Optional.empty() Hide the boilerplate of computational context Hide the boilerplate of "if non-null“ logic 22
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- 24. #JCConf Stream • for loophell ... XD • Call back hell ... XD 24
- 25. #JCConf • Stream Monad –You create Stream<T> – forEach T element – map T to Stream<U> • A simpler example Hide the boilerplate of nested loops 25
- 26. #JCConf • The flatMapoperation 4 1 1 2 3 4 5 6 flatMap(List<Integer> to Stream<Integer>) 26
- 27. #JCConf CompletableFuture • A monadis a pattern – You create M<T> – do actions on M<T> – get and map T value(s) to M<U> – do actions on M<U> or else Hide the boilerplate of computational context 27
- 28. #JCConf • Lambda rocks! •Lambda sucks!! – You create Future<T> – wait until T is ready (in another thread) – use T and the supplied code to create Future<U> Hide the boilerplate of thread logic. You‘ve done that. Future<String> 28
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- 32. #JCConf Functional Reactive Programming •Reactive • Data flow • Propagation of change • Observer • Functional • Asynchronous • … WTF? 32
- 33. #JCConf Reactive Programming • Aprogramming paradigm oriented around data flows and the propagation of change 33
- 34. #JCConf • If Javasupports reactive programming directly, it should ... • Of course, it's impossible in the language level for Java. • Model-View-Controller architecture can allow changes in the underlying model to automatically be reflected in the view (10, 15, 25) (20, 25, 35) 34
- 35. #JCConf Observer • In MVC,Model-View could be implemented by the Observer pattern. • Maybe, we can ... (10, 15, 25) (20, 25, 35) 35
- 36. #JCConf songs • When thingsbecome complex ... names albums 1900s soloartists songs songs songs songs lengths nationalities birthdays 36
- 37. #JCConf • RxJava Observable •Look up artist information • filter、flatMap? map? Stream? Observable<Artist> 37
- 38. #JCConf Functional Reactive Programming •A programming paradigm for reactive programming using the building blocks of functional programming • filter、map、reduce、flatMap are patterns from functional programming 38
- 39. #JCConf • Stream buildsup computational workflows over in-memory collections • Observable composes and sequences asynchronous and event-based systems. Instead of pulling data out, it gets pushed in • CompletableFuture is to a single value • Observable is a sequence of values 39
- 40. #JCConf Asynchronous • "that executesin whole seconds is probably doing something wrong…" - Brendan Eich • it's 100 milliseconds from research conducted by Robert Miller 40
- 41. #JCConf • Make amountain out of a molehill … XD 41
- 42. #JCConf Summary • Design patternsevolve more and more exquisitely since Java 8. • Lambda furthers advanced refactoring. • As the language evolves, so do the idioms that you use when programming. • A monad is a pattern. • Functional reactive programming is a mixture of multi patterns and paradigms. 42
- 43. #JCConf References • http://books.gotop.com.tw/v_ACL042200 • http://www.slideshare.net/JustinSDK/jdk8- functional-api •http://www.slideshare.net/mariofusco/monadic-java • http://shop.oreilly.com/product/0636920030713.do • http://en.wikipedia.org/wiki/Reactive_programming • https://github.com/ReactiveX/RxJava • https://speakerdeck.com/benjchristensen/functional -reactive-programming-with-rxjava-javaone-2013 • http://shop.oreilly.com/product/9780596802806.do 43
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