Java 8 Lambda

Transcript

1. JSR 335: Project Lambda François Sarradin -- Xebia λ
2. JSR337 Java Roadmap Java 8 aug. 2013 Java 7 jul. 2011 Java 9 ? • FP / Parallel comp. • Date API improv. • Type annotation • Compact profiles • Nashorn Modularity Performance Productivity
3. Project Lambda What's in it? Project Lambda JSR335 Collection API Bulk Operations Lambda Expression Virtual Extension Method Collection API Parallel Collections Functional API
4. Question What will be the impact of Project Lambda on the Java world?
5. Answer Look at Speed Car!
6. Planning... Presentation + live coding (free to interrupt) • Genesis • Lambda of Java • Project Lambda
7. ...And Then • Debate • Retrospective (agile style!) • Report ◦ Xebia blog ◦ Project Lambda ML
8. Genesis
9. More Processors
10. More Expressiveness More Readability 结果 汉字 = new 物().処理(); vs. fact n = product [1..n] Is it all Chinese to you?
11. FP & Competition Guava Clojure C# / F# C++
12. (Anonymous) Inner Class A λ Solution Iterables.filter(persons, new Predicate<Person>() { @Override public boolean apply(Person person) { return person.getAge() >= 18; } }); // Java + Guava
13. This is what you really need! Iterables.filter(persons, IS_ADULT); Predicate<Person> IS_ADULT = new Predicate<Person>() { @Override public boolean apply(Person person) { return person.getAge() >= 18; } }); (Anonymous) Inner Class A (better?) λ Solution
14. (Anonymous) Inner Class (Not Really) A λ Solution Average length of Java one-liner is 21 line! @DEVOPS_BORAT - 12/09/2011 • "The pain of anonymous inner classes makes us roll our eyes in the back of our heads every day." (a wise Oracle's client, 01/2011)
15. What about Oracle? • "It’s time to add closures to Java" (Mark Reinhold, 12/2009) • "Oracle's position is that Java must evolve -- carefully, of course -- in order to remain competitive." (Brian Goetz - 08/2011)
16. Lambda of Java
17. Here is the λ! (int x, int y) -> x + y (x, y) -> x + y (int x, int y) -> { return x + y; } (x, y) -> { return x + y; }
18. Other λ forms m -> { m.put("France", "Paris"); m.put("UK", "London"); m.put("USA", "Washington"); } x -> 2 * x () -> 42
19. Inner Class vs. λ Solution Iterables.filter(persons, new Predicate<Person>() { @Override public boolean apply(Person p) { return p.getAge() >= 18; } }); // Java 5-7 + Guava Iterables.filter(persons, // Java 8 + Guava p -> p.getAge() >= 18);
20. Method Reference String::valueOf // like: v -> String.valueOf(v) Integer::compare // like: (i1, i2) -> Integer.compare(i1, i2) Arrays.sort(myInts, Integer::compare)
21. Virtual Extension Method (VEM) interface Message { String getMessage() default { return "Look Ma'! Interface with code!"; } }
22. VEM Motivation Help to extend existing APIs Minimize rewrite of existing API implementation eg. Collection API eg. Hibernate Collection Implementation VEM
23. Collection API Extended java.util.functions.* java.util.streams.* Extension of Iterable, Iterator, Collection, Map, ... java.util.Optional
24. Parallel Computing As Easy as 1-2-3? myCollection.parallel() .filter(x -> ...) .map(x -> ...) .reduce((x, y) -> ...) // parallel myCollection.stream() .filter(x -> ...) .map(x -> ...) .reduce((x, y) -> ...) // sequential
25. Some kata and demos...
26. Project Lambda
27. The Dream Team ;) photo: @crazybob
28. Web Sites OpenJDK 8 Web site http://openjdk.java.net/projects/lambda/ JSR335 http://jcp.org/en/jsr/detail?id=335
29. Where to Get Java 8 Mercurial repo http://hg.openjdk.java.net/lambda/lambda Java SE 8 Early Access (with lambda) http://jdk8.java.net/lambda/
30. Mailing Lists Technical Discussion mailto:lambda-dev@openjdk.java.net http://mail.openjdk.java.net/pipermail/lambda-dev/ Libs Spec Discussion http://mail.openjdk.java.net/pipermail/lambda-libs-spec-<*>/ Spec Discussion http://mail.openjdk.java.net/pipermail/lambda-spec-<*>/
31. Around Project Lambda OpenJDK OSX Build (7 & 8) http://code.google.com/p/openjdk-osx-build/ Java 8 vs Scala: a Feature Comparison http://www.infoq.com/articles/java-8-vs-scala H. Gomez U. Peter S. van den Berg
32. Around Project Lambda In France Curious about Project Lambda ;) http://blog.xebia.fr/ [FR] http://kerflyn.wordpress.com/ JDK 8: lambdas in Action [FR] http://www.devoxx. com/display/FR12/JDK+8+demo++lambdas+in +Action Java 8 et les Lambda [FR] http://thecodersbreakfast.net/index.php? post/2012/05/30/Java-8-et-les-Lambda G. Tardif O. Croisier Guess Who?
33. Project Lambda and the Community • Transparency ◦ Presentations / Publications ◦ Source code available • Early testing by community ◦ Pre-version available ◦ AdoptOpenJDK (http://java. net/projects/adoptopenjdk/pages/AdoptOpenJDK) • Quick feedback ◦ ML, Hackdays
34. Question • Oneliner, Readability, and Debugability • Java vs. Competitors • What to do for Java 8 to be adopted in projects? • Is there a future for Java?