In 2014 I have visited the Devoxx conference in Antwerp in Belgium.

Here are some notes about it:

What is Devoxx?

• Devoxx ist a conference organized by the Belgian Java User Group.
• Belgium is trilingual (French, Flemish and German), but the conference is 100% in English.
• The location is a huge cinema complex, which guarantees for great sound, comfortable seats and excellent projectors. It is cool.
• 8 tracks, overflow for keynotes
• Well organized (at least this year), more fun than other conferences…
• sister conferences:
• Devoxx FR
• Devoxx PL
• Devoxx UK
• Voxxed (Berlin, Ticino,….)

Topics & main Sponsors

• Java / Oracle
• Android / Oracle
• Startups, Business, IT in enterprises / ING-Bank
• Java-Server, JBoss, Deployment / Redhat
• JVM-languages
• Web
• SW-Architecture
• Security
• Whatever roughly fits into these lines and is considered worth being talked about by the speaker and the organizers…

These are some of the talks that I have attended:

Scala and Java8

• Many conceptional features of Scala have become available in Java 8 with lambdas.
• Problem: different implementation and interoperability between Java and Scala.
• Development of Scala will make lambdas of Scala and Java interoperabel.

Monads

• Concept from category theory. (5% of mathematicians do algebra, 5% of algebraians do category theory, but this very abstract and very theoretical piece of math suddenly becomes interesting for functional programming. Off course our functional programming world lacks the degree of infiniteness that justifies the theory at all, but concepts can be applied anyway)
• Monoid (+, *, concat,…)
• Functor
• Monad
  Wikipedia

Wikipedia de

• 
• example: List with a functor
  is flatten: ;

Probability & Decisions

• Example: Software for automatic steering of house infrastructure
• Heuristics and probability theory
• False positives / false negatives: what hurts? (usually both)
• Very good explanation of probability theory and its use

Clojure

• Clojure is another JVM-language
• It is a Lisp-Dialekt, recognizable by its source having an abundance of opening and closing parentheses: (+ (* 3 4) (* 5 6))…
• strong support for functional programming.
• Dynamically typed (for us: Just think of everything being declared as „Object“ and implicit casts being performed prior to method calls.
• After Java itself, Scala, Groovy and Javascript it appears to me to be the fifth most common JVM-language

MapReduce

• „No one at Google uses MapReduce anymore“
• Google has replaced it with more general and more performance sensitive concepts and implementations.
• Optimized: save steps, combine them etc.
• Can be used as cloud service (Cloud Dataflow)

Key Note ING

• ING considers itself to be an „open bank“
• Not the money is lieing around openly for burglers to play with it, but they claim to be open for new ideas.
• Mobile app is the typical interface to the bank.
• IT has a lot of influence („IT driven business“)
• Feasability from the IT side is considered important
• Agile Prozesses (Scrum) vs. Enterprise IT
• IT has slowly moved to these agile processes.
• „Enterprise IT is what does not work“

Material Design

• GUI-Design with Android and Web Material Design
• Visual ideas available for both platforms
• Polymer design for Web

SW-Architecture with Spring

• Spring 4.1
• „works with WebSphere“
• DRY
• Lambda from Java8 can simplify many APIs out of the box by just replacing one-method anonymous and inner classes.
• Generic Messaging Interface (wasn’t JMS that already???)
• Caching, be careful when testing, but can be disabled.
• Test on start.spring.io
• Spring works well with Java. Also with Groovy, which comes from the same shop as spring. Combination with Scala „experimental“

Lambda_behave

• High-Level testing-Framework
• Uses Java8-Features (Lambda etc.)
• Description in natural language.
• Failure-messages are human readable
• Like Cucumber…
• Source of randomness can be configured. This is very important for monte-carlo-testing, simulations and the like.

Builtin Types of Scala and Java

• In Java we find „primitive types“ (long, int, byte, char, short, double,…)
• Probleme with arithmetic with int, long & Co: Overflow happens unnoticed
• With float and double Rounding errors
• With BigInteger, BigDecimal, Complex, Rational error prone, clumpsy and unreadable syntax.
• In Scala we can write a=b*c+d*e even for newly defined numerical types.
• Remark: Oracle-Java-guys seem to consider the idea of operator overloading for numerical types more interesting than before, as long as it is not used for multiplying exceptions with collections and the like.
• Spire library

Future of Java (9, 10, …)

Part I

• Q&A-meeting (questions asked via twitter)
• Numerical types are in issue. That primitive types behave as they do and are kind of the default won’t change.
• Generics and type erasure (where is the problem)?
• Jigsaw vs. Jars vs. OSGi still open how that will fit together, but jar is there to stay.
• Jigsaw repository: Could well be located with maven central. Oracle does not work in such a way that this being hosted directly by Oracle is likely to happen, if third party software is there as well.

Part II

• Benchmarking with Java is hard because of hot spot optimization
• JMH is a good tool
• New ideas are always hard to introduce because of the requirement of remaining compatible with old versions.
• Java might get a „repl“ some day, like irb for Ruby…

Part III

• Collection literals (promised once for Java 7!!!) did not make it into Java 8, unlikely for Java 9
• With upcoming value types this might be more reasonable to find a clean way for doing that.
• For Set and List somthing like
  new TreeSet(Arrays.asList(m1, m2, m3,…., mn))
  works already now
• For maps something like a pair would be useful. Tuples should come and they should be based on value types. The rest remains as an exercise for the reader.

Part IV

• Tail-Recursion can now be optimized in an upcoming version.
• Because of the security-manager, that analyzed stacktraces this was impossible for a long time. (weird!!!)
• C and Lisp have been doing this for decades now…
• Statement: Generics are hard, but having understood them once they become easy. So keep trying….
• Covarianz und Contravarianz (Bei Array falsch gelöst)

Part V

• Arrays 2.0: indexing with long could become an issue. Some steps towards list, but with array syntax. (studies and papers only)
• Lists have two extreme implementations: ArrayList and LinkedList. We would love to see more „sophisticated“ Lists, maybe some hybrid of both
• Checked exceptions: critical issue, it was a problem with generics and lambda. And way too many exceptions are checked, just think of whatever close()-methods can throw, that should not be checked.

Semantic source code analysis

• Useful for high level testing tools
• Static and dynamic analysis
• Dataflow analysis: unchecked data from outside, think of SQL-injection, but also CSS, HTML, JavaScript, JVM languages and byte code

Functional ideas in Java

Functional:

• Functions or methods are „first class citizens“
• Higher order functions (C could that already)
• Closures
• Immutability (function always returns the same result)
• „lazy“-constructions can be possible though
• For big structures we always have the question of immutability vs. performance
• But functional is much more thread-friendly

50 new things in Java8

Part I

• Lambda (see below)
• Streams (see below)
• Default implementations in interfaces
• Date/Time (loke Joda time)
• Optional (better than null)
• Libraries can work with lambda
• Parallel (use with care and only when needed and useful)

Part II

• String.join()
• Something like „find“ in Unix/Linux
• Writing comparators is much easier
• Maps of Maps, Maps of Collections easier
• Sorting is better: quicksort instead of mergesort, can be parallelized

Groovy for Android

• Problem with JVM languages other than Java: library has to be included in each app. 🙁
• Solution: jar optimization tool helps
• Second problem: dynamic languages have to be compiled on demand on the device
• Solution: „static“ programming, dynamic features possible but not performing well

Lambdas

• Lambdas are anonymous functions
• Idea given: interface XY with one method uvw()
• Instead of
  
XY xy = new XY() {
public long uvw(long x) { return x*x }
};

  new
  XY xy = x -> x*x;
• shorter, more readable, easier to maintain, interface becomes superfluous in many cases.
• Closure means that final variables from the surrounding context can be included
• Instance methods can be seen as closures also, the include the instance in a closure like way.

Streams

• Streams are somewhere in the vicinity of Collection, Iterable, Iterator and the like, but something new.
• They have methods that allow a function to be applied on all elements
• Elegant for programming stuff like
• Sum
• Product
• Maximum
• Minimum
• First / last / any element with certain property
• all elements with a certain property
• all transformed Elements…
• It turns out to be a wise decision to make it different from Iterable, Iterator, Collection,… and rather provide wrapping capabilities where needed.

Links

• Devoxx
• Voxxed
• Devox 2013
• Java 8 FAQ

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