Who am I? Harlan Iverson. Programming enthusiast. Seeker of truth. Imperfect. I'll be wrong about some things. Please correct me if you can.

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2 Who am I? Harlan Iverson. Programming enthusiast. Seeker of truth. Imperfect. I'll be wrong about some things. Please correct me if you can.

3 P.S... I hate boring presentations. Please, engage and stay awake! Mental note: every slide ends with 'what else?'

4 My experience in general Many JEE 5 web projects A huge Java app. Focus on rules and unit testing. A few large Javascript apps. A lot of networking stuff. LOTS of tinkering with everything. I love Open Source

5 My experience with Scala Played with Lift. Integrated with Spring and JEE. Have never used Scala in production. I'm just trying to make some fun.

6 Who are you? Programmer? Java? With a thing on the side?...looking for a thing on the side? With a dynamic language? Scala? :D

7 What is Scala? Programming language Designed by Martin Odersky Short for Scalable Language. Skay-lah, Skah-lah. It doesn't matter; OP says so. Skay-lay? Probably not First appeared in appeared in Currently 2.7.7, appeared 6 days ago. Many dynamic features, but compiles to static code. Functional-object hybrid Runs in the JVM Open Source Known best for concurrency with Actors

8 Why care about Scala? Has exciting features. Tackles XML and Concurrency in interesting ways. Ability to slowly migrate from Java Add or port individual classes to Scala Use Java classes directly Compiles to Java byte code. Your entire ecosystem is there for the taking. Just add one jar. Has a passionate community. My lifetime earnings from Scala: $0. But my soul is on top of a pyramid scheme. Lots of momentum behind alternative JVM languages. It is a GREAT platform, as we all know :) The secret is getting out.

9 What about Groovy? Groovy is probably cool. Anyone worked with it? "I can honestly say if someone had shown me the Programming in Scala book [...] back in 2003 I'd probably have never created Groovy." - James Strachan (creator of Groovy) Sounds compelling.

10 Language Features There are a lot. I will miss some, and not fully understand others. Fully Object Oriented Functional Dynamic In general the language is lean. Functionality is added through libraries.

11 Compare to Java Statically typed Compile time checking Supports class inheritance as we Java folks know it... with a few tweaks. Uses Java interfaces for List, Set, Map. Supports Generics and Annotations Annotation support is being revamped in 2.8

12 Contrast to Java Type inference No primitives... as far as the programmer knows. But the compiler is smart. No static Classes can have companion objects. No final var vs. val Public by default No class / file connection Semi-colons are optional

13 Wanna see?

14 Object oriented implicit def package import on Objects in lexical scopes Traits Mixin inheritance Option the end of null Operator overloading Friendly to DSLs. But be careful!

15 Infamous C++ features I might as well address these first. Multiple inheritance Not so evil in Scala. Coherent strategy means you know exactly what you're getting from where.... ruby programmers like it (mixin)! Infix/Postfix operator overloading Yea, avoid it unless you're writing a DSL.

16 Scala is statically typed. It is powerful like a dynamic language. But it isn't scary like a dynamically typed language. Namely: you don't need to unit test for typos. Compiles to normal Java byte code.

17 Normal byte code? Groovy/JRuby/Jython use reflection and have a 'runtime' to help out. Scala does not. It has a language library. Yes, Scala's multiple inheritance and dynamic goodness compile to static Java classes! Fire up javap, see for yourself. Performance

18 Oh, performance. On par with Java code. I don't need to convince you that Java is fast. Or hard to accurately benchmark. But for the record...

19 Quicksort 100,000 integers Java: 45ms Scala: 56ms Groovy: 12800ms Reference provided at the end

20 Ray Tracing Java vs. Scala vs. Groovy Granted you probably won't ray trace in Groovy... ray.java 12.89s ray.scala s ray.groovy 2h 31m 42s

21 LISPiness Closures Lambdas (functions as objects) Cool functional list operations Map, filter, fold, etc Pattern matching Case Classes XML For/sequence comprehensions Partial function application Higher order functions Love or hate them, no parentheses.

22 Sorry Clojure Source: xkcd.com

23 Case Classes Shorthand creates few things automatically Thanks, Scala. Extractor Objects unapply() as inverse of apply() Mutators for constructor arguments Function for creation without new There are also case Objects.

24 Libraries Actors XML Collections

25 Actors Based on academic idea for parallel programming Thread or Event based Similar style to JMS messaging Uses Fork/Join internally, being included in Java 7 There is a clustered/fault-tolerant implementation that uses Terracotta Interesting implication for web applications... more on that soon

26 Actors

27 XML XML is part of the language syntax (thanks to infix/postfix operator overloading?) Pattern matching Schema2src Pull parsing doesn't work well Can't use pattern matching on non-scala.xml nodes. Not surprising, but can be inconvenient.

28 Collections Being a functional/object hybrid is a tough job. Mutable Good for OO style Immutable Good for FP style and concurrency Java Compatibility (JCL) Typically not used directly, as conversion can happen implicitly

29 Can I still use my tools? Yes! Scala compiles to regular Java byte code. Works in Google App Engine

30 Integration with Java Tools Spring MVC Java EE 6 Maven In the central repo There is also a scala plugin JRebel Free license for Scala developers Mocking frameworks The debugger Since it's legit Java byte code.

31 Some cool Scala stuff Lift Interesting COMET support via Actors Easy to get started through Maven archetype All the advantages of being in a JVM ScalaTest Integrates several testing styles into one package Can be used for Java or Scala code Has a DSL for Spec style testing

32 IDE Support This is not the strongest point. Netbeans, IntelliJ IDEA, Eclipse plugins. But they lack support for Scala-specific Netbeans is what I know infix/postfix and unary operator syntax detection No auto-complete for Scala classes in Java code. examples...

33 Time for the bad stuff... You didn't think I'd forget about that, did you? New language, few established conventions Liberal syntax means bad code can be REALLY bad code But at least you know it does something since it is statically typed? Java interop isn't as pretty as plain Scala Namely: need to check for nulls :( Annotations don't work well in 2.7; flawless in 2.8. Binary / language compatibility and core feature stability It has changed with minor versions XML Library is awesome but doesn't support pluggable parsers / serializers /etc.

34 Getting Started Run it in your browser. (runs in Google App Engine) Download it Get an IDE plugin

35 Discuss! Source:

36 References A Tour of Scala Quicksort Benchmark Ray Tracing Benchmark Scala XML Fork/Join in Scala / Java 7 Scala Thread-less Concurrency Scala Collections for the Easily Bored

37 Resources ScalaTest Lift