1. Fly Through

2. Who?
<niklas.lindstrom@valtech.se>
@niklasl

3. Trust me?
Used dynamic langs on the JVM since 2000.
Groovy since 2004/2007

4. What?
A Dynamic Language for the JVM

5. A modern language
Inspired by best features:
Java
Ruby
Python
Smalltalk
...

6. Java
The Premise
The Platform

7. Exciting?
Modern GC
JIT
Puts hardware to good use
(mem, multi-core, I/O)

8. Java = Community
Well-established libraries (jdk, commons, ...).
Loads of opens source stuff.

9. Evolution
Groovy extends Java.
Really. 100% semantically, 90% syntactically.

10. Creative
Tools

11. What does it look like?
class First {
static void main(String[] args) {
println "You just gave me " + args[0]
}
}

12. Shorter
println "You just gave me ${args[0]}"

13. Many Variants
class Think {
String value
def getMeaning() {
"You just gave me ${value}."
}
static main(args) {
def first = args? args[0] : "nothing"
println new Think(value:first).meaning
}
}

14. Usages
Everywhere.
Groovy classes are real classes in Java.

15. Cherry-pick
● Small scripts
● API experimentation
● Tools for batch and analysis
● Tests, Specs
● Building

16. Entire applications
Seamlessly cross-compiles with Java.
Write any or all parts in Groovy, using any Java
framework.

17. Ceremony
public class Item {
private String name;
private String description;
public Item() {}
public String getName() { return name; }
public String setName(String name) {
this.name = name;
}
public String getDescription() { return description; }
public void setDescription(String description) {
this.description = description;
}
}

18. Pragmatic
class Item {
String name
String description
}

19. Compact Properties
new Date().time // same as getTime()

20. Dynamic
def v = "string.."
v = 1
assert v instanceof String

21. No cast needed
Just access methods and properties expected to
be there.

22. But..
Types have significance..

23. Type Hybrid
Dynamic refs are declared with def.
Typed refs are auto-cast & converted:
String v = 123
v.bytes[-1] == '3'

24. GroovyCastException
Date d
d = "hi!"

25. Small Values of Cool

26. Optional Parens
client.sendMessage "Message: ${msg}"
client.quit()

27. Access else null
response?.entity

28. Use all
files*.name

29. Slice
def l = ['a', 'b', 'c', 'd']
assert l[1..-2] == ['b', 'c']

30. Map Expandos
Map map = ['a': 1, b: 2]
assert map['a'] == 1
assert map.b == 2
map.c = 3
map['d'] = 3
assert map['c'] == map.d

31. Closures
Code block literals.
Syntax:
def items = ["a", "b", "c", "def"]
items.eachWithIndex { item, i ->
println "${i+1}: ${item}"
}

32. Sift and Transform
def values = ["1", "2", "12", "123"]
def some = values.findAll { it.size() > 1 }
def ints = some.collect { (it as int) * 2 }
assert ints == [24, 246]

33. GDK
new File("urls.txt").eachLine {
def url = new URL(it)
def file = new File("./${url.path}")
file.parentFile.mkdirs()
file.bytes = url.bytes
}

34. Xml...
def slurper = new XmlSlurper()
def html = slurper.parse(new File("/some.xhtml"))
html.body.'*'.each {
println it.'@id'
}

35. Spock
def "lists should be appendable"() {
given:
def a = []
when:
a << 1
then:
a == [1]
}

36. Mocks
EventHandler handler = Mock()
handler.handle(someAllowedEvent) >> true
handler.handle(_) >> false

37. Data-driven
expect:
a.toUpperCase() == b
where:
a | b
"a" | "A"
"b" | "B"
"c" | "C"
"d" | "D"

38. PowerAsserts
assert a == [1]
ERROR org.codehaus.groovy.tr...rt.PowerAssertionError:
assert a == [1]
| |
| false
[]

39. Environments

40. Scripts
$ groovy setup_db.groovy

41. REPL
$ groovysh
groovy:000> import org.apache.commons.io.*

42. Groovy Console

43. Building
Ant
Maven
Gradle

44. Grab with Grape
@Grab('org.mortbay.jetty:jetty-embedded:6.1.0')
import org.mortbay.jetty.Server
def server = new Server(8080)
server.start()

45. IDE:s
Amazing IntelliJ support.
Eclipse known to be good..

46. The Power of Prototyping
"You can use Groovy as
an exploratory language
for functionality spikes."

47. More Info
<http://groovy.codehaus.org/>
<http://spockframework.org/>
.. the web is full of groovy:
<http://groovyconsole.appspot.com/>
Groovy Style For the Java Guy

48. Thank you!

49. CC Images
Groovy-logo, "Groovy Duke"
"Tools"
"Shell"
"Tadpole"