JSR 335: Project Lambda François Sarradin -- Xebia

λ

JSR 337

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

Project Lambda What's in it?

Project Lambda

JSR335

Collection API Bulk Operations

Lambda Expression Virtual Extension Method

Collection API Parallel CollectionsFunctional API

Question

What will be the impact of Project Lambda on the Java world?

Answer Look at Speed Car!

Planning... Presentation + live coding (free to interrupt)

● Genesis

● Lambda of Java

● Project Lambda

...And Then ● Debate

● Retrospective (agile style!)

● Report ○ Xebia blog ○ Project Lambda ML

Genesis

More Processors

More Expressiveness More Readability

结果 汉字 = new 物().処理();

vs.

fact n = product [1..n]

Is it all Chinese to you?

FP & Competition

Guava

Clojure

C# / F# C++

(Anonymous) Inner Class A λ Solution

Iterables.filter(persons, new Predicate() {

@Override public boolean apply(Person person) {

return person.getAge() >= 18; }

}); // Java + Guava

This is what you really need!

Iterables.filter(persons, IS_ADULT);

Predicate IS_ADULT = new Predicate() {

@Override public boolean apply(Person person) {

return person.getAge() >= 18; }

});

(Anonymous) Inner Class A (better?) λ Solution

(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)

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)

Lambda of Java

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; }

Other λ forms

m -> { m.put("France", "Paris"); m.put("UK", "London"); m.put("USA", "Washington");

}

x -> 2 * x

() -> 42

Inner Class vs. λ Solution Iterables.filter(persons, new Predicate() {

@Override public boolean apply(Person p) {

return p.getAge() >= 18; }

}); // Java 5-7 + Guava

Iterables.filter(persons, // Java 8 + Guava p -> p.getAge() >= 18);

Method Reference

String::valueOf // like: v -> String.valueOf(v)

Integer::compare // like: (i1, i2) -> Integer.compare(i1, i2)

Arrays.sort(myInts, Integer::compare)

Virtual Extension Method (VEM)

interface Message {

String getMessage() default { return "Look Ma'! Interface with code!";

}

}

VEM Motivation

Help to extend existing APIs

Minimize rewrite of existing API implementation

eg. Collection API

eg. Hibernate Collection Implementation

VEM

Collection API Extended

java.util.functions.*

java.util.streams.*

Extension of Iterable, Iterator, Collection, Map, ...

java.util.Optional

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

Some kata and demos...

Project Lambda

The Dream Team ;)

photo: @crazybob

Web Sites

OpenJDK 8 Web site http://openjdk.java.net/projects/lambda/

JSR335 http://jcp.org/en/jsr/detail?id=335

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/

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-/

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

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?

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

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?