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Functional java 8
- 1. Functional Java 8 This Ain’t Your Daddy’s JDK Nick Maiorano 1 ThoughtFlow Solutions Inc.
- 2. About me Developer Software Architect Independent Consultant ThoughtFlow Solutions Functional Java 8 – This Ain’t Your Daddy’s JDK 2
- 3. Available April 2014 Functional Java 8 – This Ain’t Your Daddy’s JDK 3
- 4. Functional Java 8 – This Ain’t Your Daddy’s JDK 4
- 5. What’s in Java 8? Encoding enhancements Encryption updates Functional libraries Concurrency Modularization Repeating annotations New Date/Time API Concurrency updates Java 8 Lambdas Nashorn JavaScript Engine Church Performance improvements Functional Java 8 – This Ain’t Your Daddy’s JDK GC updates Collections 5
- 6. What’s in Java 8? Functional libraries Concurrency Java 8 Lambdas Church Functional Java 8 – This Ain’t Your Daddy’s JDK Collections 6
- 7. The rocky road to lambdas • • • • • • Lambdas too difficult in late 1990s BGGA project initiated in 2007 JSR 335 filed in late 2009 Had to fit type system Maintain backward compatibility Java community divided Functional Java 8 – This Ain’t Your Daddy’s JDK 7
- 8. The rocky road to lambdas • • • • To be released as part of Java 7 To be released in September 2013 To be released in March 2014 Completing 7 years of work Functional Java 8 – This Ain’t Your Daddy’s JDK 8
- 9. Functional Programming • Rooted in lambda calculus • Hastened by death of Moore’s law • Programming paradigm of the times Functional Java 8 – This Ain’t Your Daddy’s JDK 9
- 12. Organization Java Classes Vs. FP Functional Java 8 – This Ain’t Your Daddy’s JDK Functions 12
- 13. Building blocks Java Polymorphism, encapsulation, inheritance, dynamic binding Vs. FP Functional Java 8 – This Ain’t Your Daddy’s JDK Higher-order functions, currying, monads, list comprehensions 13
- 14. Algorithmic style Java Imperative: define behaviour as a series of steps Vs. FP Functional Java 8 – This Ain’t Your Daddy’s JDK Declarative: binding functions together without necessarily specifying their contents 14
- 15. State management Java Put state and behaviour together Vs. FP Functional Java 8 – This Ain’t Your Daddy’s JDK Avoid state 15
- 16. Mutability Java Supports mutability & immutability Vs. FP Functional Java 8 – This Ain’t Your Daddy’s JDK Emphasis on immutability 16
- 17. Design patterns Java Relies on design patterns to complement OOP for a higher level of abstraction Vs. FP Functional Java 8 – This Ain’t Your Daddy’s JDK Is already a higher level abstraction 17
- 18. Concurrency Java Use multi-threading, control access to shared resources via locks Vs. FP Functional Java 8 – This Ain’t Your Daddy’s JDK Organize processing into parallel workflows each dedicated to a core and avoid state, shared resources and locks 18
- 19. Recursion Java Supported with limitations Vs. FP Functional Java 8 – This Ain’t Your Daddy’s JDK Rudimentary 19
- 20. Expressiveness Java Clear & verbose Vs. FP Functional Java 8 – This Ain’t Your Daddy’s JDK Concise & dense 20
- 21. Functional Java “…Is a blend of imperative and object oriented programming enhanced with functional flavors” Functional Java 8 – This Ain’t Your Daddy’s JDK 21
- 22. Functional Java 8 – This Ain’t Your Daddy’s JDK 22
- 23. New Syntax • • • • Lambdas Functional interfaces Method references Default methods Functional Java 8 – This Ain’t Your Daddy’s JDK 23
- 24. What’s a lambda? Functional Java 8 – This Ain’t Your Daddy’s JDK 24
- 25. Anatomy of the lambda • Behavior-as-data facilitators • On-the-fly code definers • Ground-floor of FP Functional Java 8 – This Ain’t Your Daddy’s JDK 25
- 26. Anatomy of the lambda Lambda blocks (Parameter declaration) -> {Lambda body} (Integer i) -> {System.out.println(i);}; Functional Java 8 – This Ain’t Your Daddy’s JDK 26
- 27. Anatomy of the lambda Lambda blocks (Parameter declaration) -> {Lambda body} (Integer i) -> {System.out.println(i);}; Functional Java 8 – This Ain’t Your Daddy’s JDK 27
- 28. Anatomy of the lambda Lambda expressions Parameter name -> Lambda expression (Integer i) -> {System.out.println(i);}; Functional Java 8 – This Ain’t Your Daddy’s JDK 28
- 29. Anatomy of the lambda Lambda expressions Parameter name -> Lambda expression i -> System.out.println(i); Functional Java 8 – This Ain’t Your Daddy’s JDK 29
- 30. Anatomy of the lambda Lambda expressions Parameter name -> single statement; i -> i * 2; Functional Java 8 – This Ain’t Your Daddy’s JDK No return statement 30
- 31. Functional Interfaces • Lambdas are backed by interfaces • Single abstract methods • @FunctionalInterface Functional Java 8 – This Ain’t Your Daddy’s JDK 31
- 32. Functional Interfaces @FunctionalInterface public interface Calculator { int calculate(int x, int y); } Functional Java 8 – This Ain’t Your Daddy’s JDK 32
- 33. Functional Interfaces Calculator multiply = (x, y) -> x * y; Calculator divide = (x, y) -> x / y; int product = multiply.calculate(10, 20); int quotient = divide.calculate(10, 20); someMethod(multiply, divide); anotherMethod((x, y) -> x ^ y); Functional Java 8 – This Ain’t Your Daddy’s JDK 33
- 34. Functional Interfaces • Over 40 functional interfaces in JDK 8 • Rarely need to define your own • Generic and specialized Functional Java 8 – This Ain’t Your Daddy’s JDK 34
- 35. Functional Interfaces Consumer Supplier<T> T get() Supplier Functional Interfaces Consumer<T> void accept(T t); Function Function <T, R> R apply(T t); Predicate Predicate<T> boolean test(T t); Functional Java 8 – This Ain’t Your Daddy’s JDK 35
- 36. Method References Calculator maxFinder = (x, y) -> Math.max(x, y); Functional Java 8 – This Ain’t Your Daddy’s JDK 36
- 37. Method References Calculator maxFinder = Math::max; Math Calculator int max(int a, int b); int calculate(int x, int y); Functional Java 8 – This Ain’t Your Daddy’s JDK 37
- 38. Method References Type Template Static Class::method Instance instanceVariable::method Constructor Class::new Super super::method Generic constructor Class<Type>::new Array Class[]::new Functional Java 8 – This Ain’t Your Daddy’s JDK 38
- 39. Anonymous classes? • Do we still need anonymous classes? • Lambdas are behavior-only – no state • Only single abstract methods Functional Java 8 – This Ain’t Your Daddy’s JDK 39
- 40. Default Methods @FunctionalInterface public interface Calculator { int calculate(int x, int y); default int multiply(int x, int y) { return x * y; } } Functional Java 8 – This Ain’t Your Daddy’s JDK 40
- 41. Default Methods • Can be overloaded • Can be static or instance based • Introduce multiple inheritance Functional Java 8 – This Ain’t Your Daddy’s JDK 41
- 42. Functional Java 8 – This Ain’t Your Daddy’s JDK 42
- 43. Java-style functional programming • Other languages support FP natively • Java supports FP through libraries Functional interfaces Functional Java Streams Collections Functional Java 8 – This Ain’t Your Daddy’s JDK 43
- 44. Functionalized Collections Functional Java 8 – This Ain’t Your Daddy’s JDK 44
- 45. Functionalized Lists List<String> stooges = Arrays.asList("Larry", "Moe", "Curly"); stooges.forEach(s -> System.out.println(s); Functional Java 8 – This Ain’t Your Daddy’s JDK 45
- 46. Functionalized Lists List<String> stooges = Arrays.asList("Larry", "Moe", "Curly"); stooges.forEach(System.out::println); Functional Java 8 – This Ain’t Your Daddy’s JDK 46
- 47. Functionalized Lists Function<String, String> feminize = s -> "Larry".equals(s) ? "Lara" : "Moe".equals(s) ? "Maude" : "Shirley"; stooges.replaceAll(feminize); Functional Java 8 – This Ain’t Your Daddy’s JDK 47
- 48. Functionalized Lists Predicate<String> moeRemover = s -> “Moe".equals(s); stooges.removeIf(moeRemover); Functional Java 8 – This Ain’t Your Daddy’s JDK 48
- 49. Functionalized Maps Map<Integer, List<String>> movieDb = new HashMap<>(); movieDb.computeIfAbsent(1930, k -> new LinkedList<>()); movieDb.compute(1930, (k, v) -> { v.add(“Soup to nuts”); return v;}); Functional Java 8 – This Ain’t Your Daddy’s JDK 49
- 50. Functionalized Maps movieDb.putIfAbsent (1930, new LinkedList<>()); movieDb.getOrDefault (1930, new LinkedList<>()); Functional Java 8 – This Ain’t Your Daddy’s JDK 50
- 51. Streams Functional Java 8 – This Ain’t Your Daddy’s JDK 51
- 52. Streams Lambda Stream Operation 1 Functional Java 8 – This Ain’t Your Daddy’s JDK Lambda Operation 2 Lambda Operation 3 Lambda Operation 4 52
- 53. Streams Build Peek Filter Stream operations Iterate Map Reduce Functional Java 8 – This Ain’t Your Daddy’s JDK 53
- 54. Streams private static boolean isPerfect(long n) { long sum = 0; for (long i = 1; i <= n / 2; i++) { if (n % i == 0) { sum += i; } } return sum == n; } Functional Java 8 – This Ain’t Your Daddy’s JDK 54
- 55. Streams private static boolean isPerfect(long n) { return n > 0 && LongStream.rangeClosed(1, n / 2). filter(i -> n % i == 0). reduce(0, (l, r) -> l + r) == n; } Functional Java 8 – This Ain’t Your Daddy’s JDK 55
- 56. Streams • • • • Declarative constructs Can abstract any imperative for/while loop Work best when adhering to FP principles Easily parallelizable Functional Java 8 – This Ain’t Your Daddy’s JDK 56
- 57. Parallel Streams private static boolean isPerfect(long n) { return n > 0 && LongStream.rangeClosed(1, n / 2). filter(i -> n % i == 0). reduce(0, (l, r) -> l + r) == n; } Functional Java 8 – This Ain’t Your Daddy’s JDK 57
- 58. Parallel Streams private static boolean isPerfect(long n) { return n > 0 && LongStream.rangeClosed(1, n / 2). parallel(). filter(i -> n % i == 0). reduce(0, (l, r) -> l + r) == n; } Functional Java 8 – This Ain’t Your Daddy’s JDK 58
- 59. Parallel Streams Functional Java 8 – This Ain’t Your Daddy’s JDK 59
- 60. Parallel Streams Functional Java 8 – This Ain’t Your Daddy’s JDK 60
- 61. Parallel Streams • Uses fork-join used under the hood • Thread pool sized to # cores • Order can be changed Functional Java 8 – This Ain’t Your Daddy’s JDK 61
- 62. Parallel Streams private static boolean isPerfect(long n) { return n > 0 && LongStream.rangeClosed(1, n / 2). parallel(). filter(i -> n % i == 0). reduce(0, (l, r) -> l + r) == n; } Functional Java 8 – This Ain’t Your Daddy’s JDK 62
- 63. Parallel Streams private static boolean isPerfect(long n) { return n > 0 && LongStream.rangeClosed(1, n / 2). parallel(). filter(i -> n % i == 0). reduce(0, (l, r) -> l + r) == n; } List<Long> perfectNumbers = LongStream.rangeClosed(1, 8192). filter(PerfectNumberFinder::isPerfect). collect(ArrayList<Long>::new, ArrayList<Long>::add, ArrayList<Long>::addAll); Functional Java 8 – This Ain’t Your Daddy’s JDK 63
- 64. Parallel Streams private static boolean isPerfect(long n) { return n > 0 && LongStream.rangeClosed(1, n / 2). parallel(). filter(i -> n % i == 0). reduce(0, (l, r) -> l + r) == n; } List<Long> perfectNumbers = LongStream.rangeClosed(1, 8192).parallel(). filter(PerfectNumberFinder::isPerfect). collect(ArrayList<Long>::new, ArrayList<Long>::add, ArrayList<Long>::addAll); Functional Java 8 – This Ain’t Your Daddy’s JDK 64
- 65. Parallel Streams 8,128 33,550,336 8,589,869,056 137,438,691,328 Functional Java 8 – This Ain’t Your Daddy’s JDK Imperative 0 190 48648 778853 Serial Stream 1 229 59646 998776 Parallel Stream 0 66 13383 203651 65
- 66. Parallelization • Must avoid side-effects and mutating state • Problems must fit the associativity property • Ex: ((a * b) * c) = (a * (b * c)) • Must be enough parallelizable code • Performance not always better • Can’t modify local variables (unlike for loops) Functional Java 8 – This Ain’t Your Daddy’s JDK 66
- 67. Streams (the good) • • • • Allow abstraction of details Communicate intent clearly Concise On-demand parallelization Functional Java 8 – This Ain’t Your Daddy’s JDK 67
- 68. Streams (the bad) • • • • Loss of flexibility and control Increased code density Can be less efficient On-demand parallelization Functional Java 8 – This Ain’t Your Daddy’s JDK 68
- 69. Functional Java 8 – This Ain’t Your Daddy’s JDK 69
- 70. Final thoughts on Java 8 Functional Java 8 – This Ain’t Your Daddy’s JDK 70
- 71. How good is functional Java? • • • • • • Java now supports functional constructs But still OO at its core Functional expressions a little clunky Generics require more mental agility Conciseness is compromised Recursion not industrial strength Functional Java 8 – This Ain’t Your Daddy’s JDK 71
- 72. How good is functional Java? • FP integrated cohesively & coherently • New tools available for the masses Functional Java 8 – This Ain’t Your Daddy’s JDK 72
- 73. Available at Amazon April 2014 Functional Java 8 – This Ain’t Your Daddy’s JDK 73
- 74. @ThoughtFlow_Inc Functional Java 8 – This Ain’t Your Daddy’s JDK 74
- 75. Questions Functional Java 8 – This Ain’t Your Daddy’s JDK 75