Java 8: Lambdas, Monads and Java Collections

Presented during Confitura 2015

Transcript

1. JAVA 8
   LAMBDAS, MONADS && JAVA COLLECTIONS
   Grzegorz Piwowarek
   

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2. GRZEGORZ PIWOWAREK
   @PIVOVARIT
   

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3. GRZEGORZ PIWOWAREK
   @PIVOVARIT
   visionsoftondal.com
   

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4. Plan:
   -lambda expressions
   -java.util.function
   -monad
   -Optional
   -Stream
   

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5. lambda expressions
   (...) -> statement
   - Anonymous function
   

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6. lambda expressions
   x -> x + 1
   

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7. lambda expressions
   x -> x + 1
   - No type information
   

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8. lambda expressions
   x -> x + 1
   () -> 42
   () -> {return 42;}
   (x, y) -> {}
   () -> {}
   

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9. method references
   

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10. java.util.function
    

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11. java.util.function
    

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12. Function, BiFunction
    Consumer extends Function
    Supplier extends Function
    Predicate extends Function
    UnaryOperator extends Function
    BinaryOperator extends BiFunction
    

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13. Function, BiFunction
    Consumer extends Function
    Supplier extends Function
    Predicate extends Function
    UnaryOperator extends Function
    BinaryOperator extends BiFunction
    

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14. Function, BiFunction
    Consumer extends Function
    Supplier extends Function
    Predicate extends Function
    UnaryOperator extends Function
    BinaryOperator extends BiFunction
    

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15. Function, BiFunction
    Consumer extends Function
    Supplier extends Function
    Predicate extends Function
    UnaryOperator extends Function
    BinaryOperator extends BiFunction
    

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16. Function, BiFunction
    Consumer extends Function
    Supplier extends Function
    Predicate extends Function
    UnaryOperator extends Function
    BinaryOperator extends BiFunction
    

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17. MONAD
    

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19. GOOGLE IMAGES...
    

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20. ...
    

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21. MONAD
    Design pattern
    http://got-steam.com/
    

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22. Why bother? :
    Boilerplate -1
    Readability +1
    Complexity -1
    Responsibility -1
    

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23. type: M
    "unit": T -> M
    "bind": M.bind(T -> M) = M
    MONAD
    "bind": M.bind(T -> U)= M
    

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24. type: M
    "unit": T -> M
    "bind": M bind(T -> M) = M
    MONAD
    "bind": M.bind(T -> U)= M
    

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25. "bind": M bind(T -> U)= M
    What if U: M> ?
    

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26. "bind": M bind(T -> U)= M
    What if U: M> ?
    

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27. "bind": M bind(T -> U)= M
    What if U: M> ?
    http://www.ivanaborovnjak.com/project/box-in-a-box/
    

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28. Monads in Java 8
    Optional
    Stream
    CompletableFuture
    

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29. Monads in Java 8
    Optional
    Stream
    CompletableFuture
    

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30. Optional
    Encapsulation of operations
    on optional values
    

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31. Optional
    type: M
    "unit": T -> M
    "bind": M bind(T -> M) = M
    

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32. Optional
    type: Optional
    "unit": T -> M
    "bind": M bind(T -> M) = M
    

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33. Optional
    type: Optional
    "unit": Optional.ofNullable(), Optional.of()
    "bind": M bind(T -> M) = M
    

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34. Optional
    type: Optional
    "unit": Optional.ofNullable(), Optional.of()
    "bind": Optional.flatMap()
    

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35. Filtering an Optional
    .filter(Predicate)
    

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36. Unwrapping an Optional
    .get()
    .orElse(T default)
    .orElseGet(Supplier)
    .orElseThrow(Supplier)
    .ifPresent(Consumer)
    

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37. Java 7 style
    

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38. Java 8 style
    

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39. Java 8 style - flatMap
    

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40. Java 7,5 style ;)
    

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41. Java 7,5 style ;)
    

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42. Stream
    Encapsulation of operations
    on multiple items
    

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43. Stream
    type: Stream
    "unit": Stream.of(), Arrays.stream(), Collection.stream()
    "bind": Stream.flatMap()
    

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44. Stream
    

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45. Stream
    

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46. Stream
    

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47. Stream && Optional
    

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48. Stream
    lazy-initialized
    nonreusable
    

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49. intermediate operations
    .map()
    .flatMap()
    .filter()
    .peek()
    

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50. intermediate operations
    .map()
    .flatMap()
    .filter()
    .peek()
    Stream not consumed:
    does not print anything
    

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51. Java7
    

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52. Java8
    

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53. Consuming Stream
    .forEach(Consumer)
    .collect()
    .reduce(BinaryOperator)
    .allMatch(), anyMatch(), noneMatch()
    .findFirst(), findAny()
    .count()
    .toArray()
    

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54. Stream.reduce()
    

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55. Collectors
    .toList(), toMap(), toSet(), toCollection()
    .minBy(), maxBy()
    .joining()
    .partitioningBy()
    ...and many others
    

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56. Collectors.toList()
    

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57. Collectors.toMap()
    

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58. Collectors.joining()
    

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59. Debuggability?
    IntelliJ IDEA:
    - v14.0 - partial support
    - v15.0 - full support
    

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60. Stream in APIs
    BufferedReader.lines()
    Files.newDirectoryStream()
    Random.ints()
    ...
    

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61. you want more?
    

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62. https://github.com/
    jasongoodwin/better-java-monads
    

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63. Thank You!
    

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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
    

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