There are more than 50 actively worked JVM languages in existence today. Some have been ported to the JVM, whereas others were written specifically for the JVM. This hands-on session takes an introductory (but non-Hello, World) look at several JVM languages, including Java 8, Scala, Groovy, Kotlin, Ceylon, Xtend, and Clojure. It covers ZeroTurnaround’s initial experiences, including what rocked and sucked in learning each one. You don’t need any prior knowledge of these languages to attend the session. You will learn whether they are for you and will hear about some real-life experiences of trying these languages for the first time.

1. THE ADVENTUROUS
DEVELOPERS GUIDE
TO JVM LANGUAGES
SIMON MAPLE
@SJMAPLE
Monday, 30 September 13

2. Monday, 30 September 13

3. YOUR SPEAKER
SIMON MAPLE
@SJMAPLE
Monday, 30 September 13

4. MY AUDIENCE
0
25
50
75
100
Heard of the Language Used the language
Java Scala Groovy Clojure Ceylon Kotlin Xtend
Monday, 30 September 13

5. JAVA
“Most people talk about Java the language, and this may
sound odd coming from me, but I could hardly care less.
At the core of the Java ecosystem is the JVM.”
James Gosling,
creator of the Java programming language (2011, TheServerSide)
Monday, 30 September 13

6. JAVA THE JVM
“Most people talk about Java the language, and this may
sound odd coming from me, but I could hardly care less.
At the core of the Java ecosystem is the JVM.”
James Gosling,
creator of the Java programming language (2011, TheServerSide)
Monday, 30 September 13

7. LANGUAGES BUILT FOR THE JVM
Monday, 30 September 13

8. LANGUAGES PORTED TO THE JVM
Monday, 30 September 13

9. R.I.P ?
Monday, 30 September 13

10. Monday, 30 September 13

11. Monday, 30 September 13

12. JAVA 8
1. DON’T BREAK BINARY COMPATIBILITY
2.AVOID INTRODUCING SOURCE INCOMPATIBILITIES
3. MANAGE BEHAVIORAL COMPATIBILITY CHANGES
Monday, 30 September 13

13. LET’S EXPERIMENT
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14. Monday, 30 September 13

15. COMPANION CLASS
THERE IS NO STATIC
import HttpServer._
// import statics from companion object
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16. VARIABLES
THERE IS NO FINAL
val name: Type = initializer // immutable value
var name: Type = initializer // mutable variable
Monday, 30 September 13

17. CASE CLASS
case class Status(code: Int, text: String)
case method @ ("GET" | "HEAD") =>
...
case method =>
respondWithHtml(
Status(501,
"Not Implemented"),
title = "501 Not Implemented",
) body = <H2>501 Not Implemented: { method } method</H2>
...
Monday, 30 September 13

18. STRINGS
val header = s"""
|HTTP/1.1 ${status.code} ${status.text}
|Server: Scala HTTP Server 1.0
|Date: ${new Date()}
|Content-type: ${contentType}
|Content-length: ${content.length}
""".trim.stripMargin + LineSep + LineSep
Monday, 30 September 13

19. NULL
def toFile(file: File, isRetry: Boolean = false): Option[File] =
if (file.isDirectory && !isRetry)
toFile(new File(file, DefaultFile), true)
else if (file.isFile)
Some(file)
else
None
Monday, 30 September 13

20. COMPLEXITY
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21. Monday, 30 September 13

22. Monday, 30 September 13

23. Monday, 30 September 13

24. Monday, 30 September 13

25. JAVA SUPERCHARGED!
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26. NULL
def streetName = user?.address?.street
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27. ELVIS LIVES
def displayName = user.name ?: "Anonymous"
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28. CLOSURES
square = { it * it }
[ 1, 2, 3, 4 ].collect(square) // [1, 4, 9, 16]
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29. COLLECTIONS
def names = ["Ted", "Fred", "Jed", "Ned"]
5p[5 println names //[Ted, Fred, Jed, Ned]
def shortNames = names.findAll { it.size() <= 3 }
shortNames.each { println it } // Ted
// Jed
// Ned
Monday, 30 September 13

30. GROOVY 2.0 - DYNATIC
void someMethod() {}
void test() {
sommeeMethod()
}
Monday, 30 September 13

31. GROOVY 2.0 - DYNATIC
void someMethod() {}
void test() {
sommeeMethod()
}
import groovy.transform.TypeChecked
@TypeChecked
Monday, 30 September 13

32. GROOVY 2.0 - DYNATIC
void someMethod() {}
void test() {
sommeeMethod()
}
// compilation error:
// cannot find matching method sommeeMethod()
import groovy.transform.TypeChecked
@TypeChecked
Monday, 30 September 13

33. Monday, 30 September 13

34. Founder/CEO Jevgeni “Hosselhuff” Kabanov gets ready to save
more Java developers from redeploy madness with JRebel
YEH, WE SAVE LIVES
Monday, 30 September 13

35. Monday, 30 September 13

36. REPL
<Python user> Can you believe these JVM geeks think this is impressive?
<Perl user> Tell me about it! Welcome to the 90s
<Python user> Yeh, “Hey the 20th century called to say they wanted their code back”!
<Groovy user> Hey, we do this too!
Monday, 30 September 13

37. FUNCTIONAL PRINCIPLES
1. LITTLE OR NO SIDE EFFECTS
2. FUNCTIONS SHOULD ALWAYS RETURN THE SAME
RESULT IF CALLED WITH THE SAME PARAMETERS
3. NO GLOBALVARIABLES
4. FUNCTIONS AS FIRST ORDER CITIZENS
5. LAZY EVALUATION OF EXPRESSIONS
Monday, 30 September 13

38. WHOA!
(defn send-html-response
"Html response"
[client-socket status title body]
(let [html (str "<HTML><HEAD><TITLE>"
title "</TITLE></HEAD><BODY>" body "</BODY></HTML>")]
send-http-response client-socket status "text/html"
(.getBytes html "UTF-8"))
))
Monday, 30 September 13

39. LET’S GET FUNCTIONAL
(defn process-request
"Parse the HTTP request and decide what to do"
[client-socket]
(let [reader (get-reader client-socket) first-line
(.readLine reader) tokens (clojure.string/split first-line #"s+")]
(let [http-method (clojure.string/upper-case
(get tokens 0 "unknown"))]
(if (or (= http-method "GET") (= http-method "HEAD"))
(let [file-requested-name (get tokens 1 "not-existing")
[...]
Monday, 30 September 13

40. INTEROP
(ns clojure-http-server.core
(:require [clojure.string])
(:import (java.net ServerSocket SocketException) (java.util Date)
(java.io PrintWriter BufferedReader InputStreamReader BufferedOutputStream)))
Monday, 30 September 13

41. Monday, 30 September 13

42. LET’S EXPERIMENT
Monday, 30 September 13

43. Monday, 30 September 13

44. LET’S EXPERIMENT
Monday, 30 September 13

45. Monday, 30 September 13

46. LET’S EXPERIMENT
Monday, 30 September 13

47. SUMMARY
FUNCTIONS ARE
FIRST CLASS CITIZENS
AND SHOULD BE TREATED AS SUCH!
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48. SUMMARY
STATICALLY TYPED LANGUAGES ROCK
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49. SUMMARY
EVERYONE’S SYNTAX SUCKS...
Monday, 30 September 13

50. SUMMARY
EVERYONE’S SYNTAX SUCKS...
TO SOMEONE ELSE.
Monday, 30 September 13

51. SUMMARY
THE JVM IS AWESOME
Monday, 30 September 13

52. BE ADVENTUROUS!
Monday, 30 September 13

53. YOU, ONE HOUR LATER
0
25
50
75
100
Heard of the Lang
Java Scala Groovy Clojure Ceylon Kotlin Xtend
Monday, 30 September 13

54. REBEL LABS == AWESOME
99.9% NON-PRODUCT RELATED
TECH REPORTS WRITTEN BY
OUR DEVELOPERS
Monday, 30 September 13

55. REBEL LABS == AWESOME
JAVA 8,
CONTINUOUS DELIVERY,
APP SERVER DEBATE,
JVM WEB FRAMEWORKS,
PRODUCTIVITY REPORTS...
Monday, 30 September 13

56. REBEL LABS == AWESOME
AND...
THE ADVENTUROUS DEVELOPERS
GUIDE TO JVM LANGUAGES
Monday, 30 September 13

57. RESOURCES
HTTPSERVER EXAMPLES OF EACH LANGUAGE ON GITHUB
https://github.com/zeroturnaround/jvm-languages-report
THE ADVENTUROUS DEVELOPERS GUIDE TO JVM LANGUAGES
http://zeroturnaround.com/rebellabs/devs/the-
adventurous-developers-guide-to-jvm-languages/
Monday, 30 September 13

58. RESOURCES
SIMON MAPLE
@SJMAPLE
Monday, 30 September 13

59. Monday, 30 September 13