Here are a few thoughts in response to your questions: - Lambda expressions will significantly improve readability and reduce noise in Java code by allowing for more concise one-liners compared to anonymous inner classes. However, debugging lambdas could potentially be more challenging since they are anonymous by nature. Tools and IDE support will need to evolve to help with this. - With features like lambdas and default methods, Java 8 aims to become more competitive with languages like C# and Scala that already have closures and functional capabilities. However, Java's large existing code base and ecosystem give it advantages over newer languages. - For Java 8 to be widely adopted, projects should start evaluating and migrating to it as early access

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

2. Java Roadmap
337
Java 7 JSR Java 8
jul. 2011 aug. 2013 Java 9
?
Modularity
Performance ● FP / Parallel comp.
Productivity ● Date API improv.
● Type annotation
● Compact profiles
● Nashorn

3. Project Lambda
What's in it?
Project
Lambda
JSR335
Virtual Extension
Lambda Expression
Method
Collection API Collection API
Functional API
Parallel Collections 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>() {
@Override
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>() {
@Override
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 21 line!
@DEVOPS_BORAT - 12/09/2011

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>() {
@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
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 ;)
photo: @crazybob

28. Web Sites
JSR335
http://jcp.org/en/jsr/detail?id=335
OpenJDK 8 Web site
http://openjdk.java.net/projects/lambda/

29. Where to Get Java 8
Java SE 8 Early Access (with lambda)
http://jdk8.java.net/lambda/
Mercurial repo
http://hg.openjdk.java.net/lambda/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/
H. Gomez
Java 8 vs Scala: a Feature
Comparison
http://www.infoq.com/articles/java-8-vs-scala
S. van den Berg
U. Peter

32. Around Project Lambda
In France
JDK 8: lambdas in Action [FR]
http://www.devoxx. O. Croisier
com/display/FR12/JDK+8+demo++lambdas+in
+Action
G. Tardif
Java 8 et les Lambda [FR]
http://thecodersbreakfast.net/index.php?
post/2012/05/30/Java-8-et-les-Lambda
Curious about Project Lambda ;)
http://blog.xebia.fr/ [FR]
http://kerflyn.wordpress.com/ 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?