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Java 8 - Return of the Java
Java 8 introduces significant features including lambda expressions, method references, extension methods, and a new date and time API. It streamlines coding with new functionalities such as streams for efficient data processing and sorting, enhancing overall programming experience. Additionally, performance improvements and compatibility with existing types make Java 8 a substantial upgrade for developers.
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Java 8 - Return of the Java
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- 2. Java 8 –what’s new? Lambdas, Extension Methods, SAMs, Streams, Method Handles, Oh My! Nashorn JS engine JSR-310: Date & time API No more PermGen– where classloaders go to die ... !2
- 3. Java 8 –what’s new? Lambdas, Extension Methods, SAMs, Streams, Method Handles, Oh My! Nashorn JS engine JSR-310: Date & time API No more PermGen– where classloaders go to die ... !3
- 4. Your Mission Should youchoose to accept it Sort a list of people by their names
- 5. Java 7 Collections.sort(people, newComparator<Person>() { public int compare(Person x, Person y) { return x.getName().compareTo(y.getName()); } }); !5
- 6. We are notamused © Fredrik Vraalsen 2012
- 7. Java 8 Comparator<Person> byName= new Comparator<Person>() { public int compare(Person x, Person y) { return x.getName().compareTo(y.getName()); } }; Single Abstract Method ! (SAM) !7
- 8. Single Abstract Method Interfacewith only one (non-default) method Abstract class with only one abstract method Sound familiar? Pretty much every event listener, callback mechanism, ... Can be replaced by a Lambda !8
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- 10. SAM Comparator<Person> byName =new Comparator<Person>() { public int compare(Person x, Person y) { return x.getName().compareTo(y.getName()); } }; !10
- 11. SAM Comparator<Person> byName =new Comparator<Person>() { public int compare(Person x, Person y) { return x.getName().compareTo(y.getName()); } }; BodyReturn type Parameter list Method name Type !11
- 12. Lambda Comparator<Person> byName =new Comparator<Person>() { public int compare(Person x, Person y) { return x.getName().compareTo(y.getName()); } }; BodyReturn type Parameter list Method name Type !12
- 13. Lambda Comparator<Person> byName = ! returnx.getName().compareTo(y.getName()); }; BodyReturn type? Parameter list (Person x, Person y) -> { !13
- 14. Lambda Comparator<Person> byName = (Personx, Person y) -> Parameter list BodyReturn type? x.getName().compareTo(y.getName()); { }; return !14
- 15. Lambda Comparator<Person> byName = Parameterlist BodyReturn type? (x, y) -> x.getName().compareTo(y.getName());(Person x, Person y) !15
- 16. Lambda Comparator<Person> byName = (x,y) -> x.getName().compareTo(y.getName()); ! Collections.sort(people, byName); !16
- 17. Lambda Comparator<Person> byName = (x,y) -> x.getName().compareTo(y.getName()); ! sort(people, byName); !17
- 18. Lambda ! ! ! sort(people, (x, y)-> x.getName().compareTo(y.getName())); !18
- 19. Comparators import static java.util.Comparator.comparing; … ! sort(people,comparing((Person p) -> p.getName()); !19
- 20. Cool! ! ! ! ! Now onwards... ©Fredrik Vraalsen 2013
- 21. Method handles Reference tomethods Can be used in place of lambdas !21
- 22. Method handles ! ! ! sort(people, comparing((Personp) -> p.getName())); !22
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- 24. Ok, nice... What else? ©Fredrik Vraalsen 2012
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- 27. Extension methods !27 java.util.List: ! default voidsort(Comparator<? super E> c)
- 28. Extension methods Defender Method DefaultMethod (Virtual) Extension Method !28 java.util.List: ! default void sort(Comparator<? super E> c)
- 29. Extension methods java.util.List: ! default voidsort(Comparator<? super E> c) { } ! Defender Method Default Method (Virtual) Extension Method !29
- 30. Extension methods java.util.List: ! default voidsort(Comparator<? super E> c) { Collections.sort(this, c); } ! Defender Method Default Method (Virtual) Extension Method !30
- 31. Java 8 extensionmethods Extend interfaces with new methods Compatibility Default implementation Override Requires modification of original interface !31
- 32. C# extension methods “Add”methods to existing types Without modifying original type Defined as static methods Called as instance methods !32
- 33. Scala implicit classes “Add”methods or properties to existing types Without modifying original type Implicit wrapper object !33
- 34. Java 7 vs8 Collections.sort(people, new Comparator<Person>() { public int compare(Person x, Person y) { return x.getName().compareTo(y.getName()); } }); ! vs ! people.sort(comparing(Person::getName)); !34
- 35. So far, sogood? Lambdas Method handles Extension methods !35
- 36. So, what’s thecatch? © Fredrik Vraalsen 2012
- 37. What’s wrong withusing List::sort ? Modifies existing collection Others may be using it? Concurrency issues Performance !37
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- 39. The old fashionedway !39 List<RoadData> filtered = new ArrayList<>(); int count = 0; for (Iterator<RoadData> i = roadData.iterator(); i.hasNext() && count < 10; ) { RoadData data = i.next(); if (data.getName().contains(nameQuery)) { filtered.add(data); count++; } }
- 40. Streams !40 ! roadData.stream() .filter(r ->r.getName().contains(nameQuery)) .limit(10) .collect(Collectors.toList());
- 41. Streams – pipelines !41 ! roadData.stream() .filter(r -> r.getName().contains(nameQuery)) .limit(10) .collect(Collectors.toList()); ! ! cat roadData.txt | grep … | head > output.txt
- 42. Streams – pipelines Source collection,array, generator function, IO channel, ... Intermediate operations (Stream-producing) filter, map, ... Terminal operations (value-producing) !42
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- 44. Streams – performance ! people.stream() .filter(p-> p.getAge() >= 18) .map(Person::getName) .collect(Collectors.toList()); !44
- 45. This one goesto 11! ! people.parallelStream() .filter(p -> p.getAge() >= 18) .map(Person::getName) .collect(Collectors.toList()); !45
- 46. Scala FTW! ! people.par .filter(_.age >=18) .map(_.name) !46
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- 48. More cool stuffin Java 8 String join Collection removeIf (≈ filter) List sort Map getOrDefault, putIfAbsent, replace, forEach, etc. java.util.stream.Collectors count, sum, average, min, max, groupingBy, etc. java.nio.file.Files lines !48
- 49. What’s missing? © FredrikVraalsen 2012
- 50. What’s missing? Immutability Value types Datastructures (lists, maps, etc.) Concurrency !50
- 51. Some help tobe found Immutable collections Google Guava, FunctionalJava, clj-ds Concurrency mechanisms Akka (Actors, STM) !51
- 52. github.com/krukow/clj-ds PersistentVector<Person> people =Persistents.vector( new Person("Fredrik", 37), new Person("Hedda", 2)); !52
- 53. github.com/krukow/clj-ds PersistentVector<Person> people =Persistents.vector( new Person("Fredrik", 37), new Person("Hedda", 2)); ! PersistentVector<Person> morePeople = people.plus(new Person("Johannes", 4)); !53
- 54. github.com/krukow/clj-ds PersistentVector<Person> people =Persistents.vector( new Person("Fredrik", 37), new Person("Hedda", 2)); ! PersistentVector<Person> morePeople = people.plus(new Person("Johannes", 4)); ! morePeople.stream() .forEach(p -> System.out.println(p.getName())); !54
- 55. Ready to make thejump!? © Fredrik Vraalsen 2013
- 56. Play with it! Download– http://www.oracle.com/technetwork/java/ … or https://jdk8.java.net/download.html Whitepapers – http://openjdk.java.net/projects/lambda/ FAQ – http://www.lambdafaq.org/ Supported in IntelliJ IDEA 12 & 13 Eclipse Java 8 beta plugin and NetBeans 8.0 RC !56
- 57. Why use Xinstead? Java 8 just released Will be a long time before you can use it in enterprise dev! Clojure and Scala available NOW! (JDK 1.6) Important things are still missing !57
- 58. Want to knowmore? ^{Oslo "Socially Functional Programmers" #OsloSFP} “Haskell på godt og vondt” – tonight 6pm @ Teknologihuset http://www.meetup.com/Oslo-Socially-Functional/ Functional Programming in Java 8 http://2014.flatmap.no/ !58
- 59. Questions? © Fredrik Vraalsen2012 vraalsen@iterate.no / @fredriv