Java 8: Lambdas, Monads and Java Collections

Presented during Confitura 2015

Transcript

1. JAVA 8 LAMBDAS, MONADS && JAVA COLLECTIONS Grzegorz Piwowarek
2. GRZEGORZ PIWOWAREK @PIVOVARIT
3. GRZEGORZ PIWOWAREK @PIVOVARIT visionsoftondal.com
4. Plan: -lambda expressions -java.util.function -monad -Optional -Stream
5. lambda expressions (...) -> statement - Anonymous function
6. lambda expressions x -> x + 1
7. lambda expressions x -> x + 1 - No type information
8. lambda expressions x -> x + 1 () -> 42 () -> {return 42;} (x, y) -> {} () -> {}
9. method references
10. java.util.function
11. java.util.function
12. Function<T, R>, BiFunction<T,U,R> Consumer<T> extends Function<T,Void> Supplier<T> extends Function<Void, T> Predicate<T> extends Function<T, Boolean> UnaryOperator<T> extends Function<T, T> BinaryOperator<T> extends BiFunction<T,T,T>
13. Function<T, R>, BiFunction<T,U,R> Consumer<T> extends Function<T,Void> Supplier<T> extends Function<Void, T> Predicate<T> extends Function<T, Boolean> UnaryOperator<T> extends Function<T, T> BinaryOperator<T> extends BiFunction<T,T,T>
14. Function<T, R>, BiFunction<T,U,R> Consumer<T> extends Function<T,Void> Supplier<T> extends Function<Void, T> Predicate<T> extends Function<T, Boolean> UnaryOperator<T> extends Function<T, T> BinaryOperator<T> extends BiFunction<T,T,T>
15. Function<T, R>, BiFunction<T,U,R> Consumer<T> extends Function<T,Void> Supplier<T> extends Function<Void, T> Predicate<T> extends Function<T, Boolean> UnaryOperator<T> extends Function<T, T> BinaryOperator<T> extends BiFunction<T,T,T>
16. Function<T, R>, BiFunction<T,U,R> Consumer<T> extends Function<T,Void> Supplier<T> extends Function<Void, T> Predicate<T> extends Function<T, Boolean> UnaryOperator<T> extends Function<T, T> BinaryOperator<T> extends BiFunction<T,T,T>
17. MONAD
19. GOOGLE IMAGES...
20. ...
21. MONAD Design pattern http://got-steam.com/
22. Why bother? : Boilerplate -1 Readability +1 Complexity -1 Responsibility -1
23. type: M<T> "unit": T -> M<T> "bind": M<T>.bind(T -> M<U>) = M<U> MONAD "bind": M<T>.bind(T -> U)= M<U>
24. type: M<T> "unit": T -> M<T> "bind": M<T> bind(T -> M<U>) = M<U> MONAD "bind": M<T>.bind(T -> U)= M<U>
25. "bind": M<T> bind(T -> U)= M<U> What if U: M<?> ?
26. "bind": M<T> bind(T -> U)= M<U> What if U: M<?> ?
27. "bind": M<T> bind(T -> U)= M<U> What if U: M<?> ? http://www.ivanaborovnjak.com/project/box-in-a-box/
28. Monads in Java 8 Optional Stream CompletableFuture
29. Monads in Java 8 Optional Stream CompletableFuture
30. Optional Encapsulation of operations on optional values
31. Optional type: M<T> "unit": T -> M<T> "bind": M<T> bind(T -> M<U>) = M<U>
32. Optional type: Optional<T> "unit": T -> M<T> "bind": M<T> bind(T -> M<U>) = M<U>
33. Optional type: Optional<T> "unit": Optional.ofNullable(), Optional.of() "bind": M<T> bind(T -> M<U>) = M<U>
34. Optional type: Optional<T> "unit": Optional.ofNullable(), Optional.of() "bind": Optional.flatMap()
35. Filtering an Optional .filter(Predicate<T>)
36. Unwrapping an Optional .get() .orElse(T default) .orElseGet(Supplier<T>) .orElseThrow(Supplier<Ex>) .ifPresent(Consumer<T>)
37. Java 7 style
38. Java 8 style
39. Java 8 style - flatMap
40. Java 7,5 style ;)
41. Java 7,5 style ;)
42. Stream Encapsulation of operations on multiple items
43. Stream type: Stream<T> "unit": Stream.of(), Arrays.stream(), Collection.stream() "bind": Stream.flatMap()
44. Stream
45. Stream
46. Stream
47. Stream && Optional
48. Stream lazy-initialized nonreusable
49. intermediate operations .map() .flatMap() .filter() .peek()
50. intermediate operations .map() .flatMap() .filter() .peek() Stream not consumed: does not print anything
51. Java7
52. Java8
53. Consuming Stream .forEach(Consumer<T>) .collect() .reduce(BinaryOperator<T>) .allMatch(), anyMatch(), noneMatch() .findFirst(), findAny() .count() .toArray()
54. Stream.reduce()
55. Collectors .toList(), toMap(), toSet(), toCollection() .minBy(), maxBy() .joining() .partitioningBy() ...and many others
56. Collectors.toList()
57. Collectors.toMap()
58. Collectors.joining()
59. Debuggability? IntelliJ IDEA: - v14.0 - partial support - v15.0 - full support
60. Stream in APIs BufferedReader.lines() Files.newDirectoryStream() Random.ints() ...
61. you want more?
62. https://github.com/ jasongoodwin/better-java-monads
63. Thank You!
64. REFERENCES: -"MONADIC JAVA" BY MARIO FUSCO -"WHAT'S WRONG WITH JAVA 8" BY PIERRE-YVES SAUMONT -WWW.ORACLE.COM -"A FISTFUL OF MONADS" - LEARN YOU A HASKELL FOR GREAT GOOD