JSR 335: Project Lambda. François Sarradin -- Xebia

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1 λ JSR 335: Project Lambda François Sarradin -- Xebia

2 Java Roadmap Java 7 jul JSR Java 8 aug Java 9? Modularity Performance Productivity FP / Parallel comp. Date API improv. Type annotation Compact profiles Nashorn

3 Project Lambda What's in it? Project Lambda JSR335 Lambda Expression Functional API Collection API Parallel Collections Virtual Extension Method Collection API Bulk Operations

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 Clojure C++ C# / F# Guava

12 (Anonymous) Inner Class A λ Solution Iterables.filter(persons, new Predicate<Person>() public boolean apply(person person) { return person.getage() >= 18; } }); // Java + Guava

13 (Anonymous) Inner Class A (better?) λ Solution Iterables.filter(persons, IS_ADULT); Predicate<Person> IS_ADULT = new Predicate<Person>() public boolean apply(person person) { return person.getage() >= 18; } }); This is what you really need!

14 (Anonymous) Inner Class (Not Really) A λ Solution "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) Average length of Java one-liner is /09/2011

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) -> { return x + y; } (x, y) -> { return x + y; } (int x, int y) -> x + y (x, y) -> x + y

18 Other λ forms x -> 2 * x () -> 42 m } -> { m.put("france", "Paris"); m.put("uk", "London"); m.put("usa", "Washington");

19 Inner Class vs. λ Solution Iterables.filter(persons, new Predicate<Person>() public boolean apply(person p) { return p.getage() >= 18; } }); // Java 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 VEM eg. Collection API Help to extend existing APIs Minimize rewrite of existing API implementation eg. Hibernate Collection Implementation

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.stream().filter(x ->...).map(x ->...).reduce((x, y) ->...) // sequential mycollection.parallel().filter(x ->...).map(x ->...).reduce((x, y) ->...) // parallel

25 Some kata and demos...

26 Project Lambda

27 The Dream Team ;)

28 Web Sites JSR335 OpenJDK 8 Web site

29 Where to Get Java 8 Java SE 8 Early Access (with lambda) Mercurial repo

30 Mailing Lists Technical Discussion Libs Spec Discussion Spec Discussion

31 Around Project Lambda OpenJDK OSX Build (7 & 8) H. Gomez Java 8 vs Scala: a Feature Comparison S. van den Berg U. Peter

32 Around Project Lambda In France JDK 8: lambdas in Action [FR] com/display/fr12/jdk+8+demo++lambdas+in +Action O. Croisier G. Tardif Java 8 et les Lambda [FR] post/2012/05/30/java-8-et-les-lambda Curious about Project Lambda ;) [FR] Guess Who?

33 Project Lambda and the Community Transparency Presentations / Publications Source code available Early testing by community Pre-version available AdoptOpenJDK ( 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?