DevNexus 2018: Learn Java 8, lambdas and functional programming
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The document outlines significant developments in Java versions from 5 to 8, highlighting key features such as generics, syntactic sugar, and the introduction of lambdas and a new date API in Java 8. It also covers improvements in class mocking and proxying, as well as functional programming concepts related to lambda calculus. Notably, it emphasizes the evolution of Java's file I/O operations and error handling through various versions.
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Date / Time API (example)
LocalDateTime now = LocalDateTime.now();
String thatSpecialDay = now
.withDayOfMonth(1)
.atZone(ZoneId.of("Europe/Paris"))
.plus(Duration.ofDays(5))
.format(DateTimeFormatter.ISO_ZONED_DATE_TIME);
System.out.println(thatSpecialDay);
Output
2016-09-06T17:45:22.488+01:00[Europe/Paris]](https://image.slidesharecdn.com/20180223-learnjava8devnexus-180223163534/85/DevNexus-2018-Learn-Java-8-lambdas-and-functional-programming-26-320.jpg)
DevNexus 2018: Learn Java 8, lambdas and functional programming
- 1. © Henri Tremblay 2015 Henri Tremblay Senior Software Engineer Terracotta, a Software AG company Learn Java 8: Lambdas and Functional Programming @henri_tremblay
- 4. 4 Henri Tremblay • More or less made possible class mocking and proxying • Coined the term “partial mocking”
- 5. 5 Henri Tremblay • More or less made possible class mocking and proxying • Coined the term “partial mocking”
- 6. 6
- 7. 7 Java < 8
- 9. 9 Questions
- 10. 10 Java 5 (2004)
- 11. 11 JAVA 5 GAVE THE GENERIC TYPES TO THE WORLD (and also annotations, concurrent collections, enum types, for each, static imports and so on and so on)
- 12. 12 Type witness Having <T> T anyObject() you can force the type with MyClass.<List<String>> anyObject() because (List<String>) MyClass.anyObject() gives a warning
- 13. 13 Java 6 (2006, last from Sun)
- 14. 14 JAVA 6 BROUGHT... PRETTY MUCH NOTHING (a bunch of performance improvements under the hood, better xml parsing and the first scripting api)
- 15. 15 Java 7 (2011, first from Oracle)
- 16. 16 JAVA 7 BROUGHT A LOT OF SYNTACTIC SUGAR (plus invokeDynamic, ForkJoin, better file IO)
- 17. 17 Switch for strings switch(s) { case "hello": return "world"; case "bonjour": return "le monde"; }
- 18. 18 Diamond operator List<String> list = new ArrayList<>();
- 19. 19 Binary integer literals and underscores int i = 0b1110001111; int i = 1_000_000;
- 20. 20 Multiple catches try { // ... do stuff } catch (IOException | SerializationException e) { log.error("My error", e); } Instead of try { // ... do stuff } catch (IOException e) { log.error("My error", e); } catch (SerializationException e) { log.error("My error", e); }
- 21. 21 Auto Closeable Before InputStream in = new FileInputStream("allo.txt"); try { // … do stuff } finally { try { in.close(); } catch(IOException e) {} } After try(InputStream in = new FileInputStream("allo.txt")) { // … do stuff }
- 22. 22 File IO API List<String> lines = Files.readAllLines( Paths.get("path", "to", "my", "file.txt")); // also: file watcher, symbolic links, file locks, // copy… Look in java.nio.file
- 23. 23 Java 8 (2014)
- 24. 24 JAVA 8: LAMBDA! (and also a new date API, default methods, metaspace, Nashorn, JavaFX and CompletableFuture)
- 25. 26 Date / Time API Core ideas: Immutable A time is a time, a date is a date. Not always both (like java.util.Date) Not everyone uses the same calendar (the same Chronology) LocalDate, LocalTime, LocalDateTime Local. No time zone OffsetDateTime, OffsetTime Time with an offset from Greenwich ZonedDateTime LocalDateTime with a time zone Duration, Period Time span Instant Timestamp Formatting Easy and thread-safe formatting
- 26. 27 Date / Time API (example) LocalDateTime now = LocalDateTime.now(); String thatSpecialDay = now .withDayOfMonth(1) .atZone(ZoneId.of("Europe/Paris")) .plus(Duration.ofDays(5)) .format(DateTimeFormatter.ISO_ZONED_DATE_TIME); System.out.println(thatSpecialDay); Output 2016-09-06T17:45:22.488+01:00[Europe/Paris]
- 27. 28
- 28. 29 Lambda: 11th letter of the Greek alphabet
- 29. 30 (also written as λ-calculus) is a formal system in mathematical logic for expressing computation based on function abstraction and application using variable binding and substitution. It is a universal model of computation that can be used to simulate any single- taped Turing machine and was first introduced by mathematician Alonzo Church in the 1930s as part of an investigation into the foundations of mathematics. Lambda calculus
- 30. 31 This is a function: This is a lambda: Lambda calculus
- 31. 32 c = sqrt(add(pow(a, 2), pow(b, 2))) Functional programming
- 32. 33
- 33. 45 The End
- 34. 46 Who has learned something today? ?
- 35. 47 Brian Goetz – State of the lambda http://cr.openjdk.java.net/~briangoetz/lambda/lambda-state- final.html http://cr.openjdk.java.net/~briangoetz/lambda/lambda- translation.html Ninja Squad – Lambda Kata https://github.com/Ninja-Squad/ninjackaton-lambda Maurice Naftalin’s lambda facts and books http://www.lambdafaq.org/ Mastering Lamdbas: Java Programming in a Multicore World Links