Groovy is a dynamic programming language for the Java Virtual Machine that aims to be more concise and productive for the Java developer. It builds upon Java by adding features like dynamic typing, closures, operator overloading, and GStrings. Groovy can be used for scripting, unit testing, configuration management, and full applications through frameworks like Grails and Griffon.

1. Introduction to Groovy
The next generation JVM programming language

2. What is Groovy?
• Scripting language
• Programming Language
• runs on JVM
• dynamic
• derived from Java
• JSR-241
• started from 2003

3. Problem with Java
• Primitive data types, defies the nature of OO
programming

4. Why Groovy
• Easier than Java syntax
• Fully compatible with Java
• Easy to find workarounds since Java code can be
compiled
• Principle of least surprises

5. Use Cases
• Scripting instead of Sh, Perl, Python, Ruby, etc
• Simpler ways of writing unit tests, stub and mocks
• Configuration/Dependency Management in Gradle
!
• Full blown applications via Grails and Griffon

6. Groovy Features
Everything is an object, including numbers
Example:
5.times{
println “ho”
}
(NOTE: Curly braces is a Closure)

7. Groovy Features
• Dynamic data type / Explicit typing
def b = 2
def is a reference, asks the compiler to figure out for
itself.

8. Groovy Features
• Objects
new User(name: ‘Kevin’, email:’kevin@kevin.com’)

9. Groovy Features
• Collections
New collection type - Range
Eg.
1..5 (inclusive, range from 1 to 5) or
1..<5 (exclusive, range from 1 to 4)

10. Groovy Features
• Collections
Iterator, eg.
r.each { n->
println n
}
or
r.each { println it }
(where ‘it’ is a reserved word)

11. Groovy Features
• Syntactic sugar for List
def countries = [“Malaysia”, “Thailand”]

12. Groovy Features
• Adding or removing values
list += “Singapore” becomes [“Malaysia”, “Thailand”,
“Singapore”]
!
list = list - [“Singapore”] becomes [“Malaysia”,
“Thailand”]

13. Groovy Features
Map
def person = [name:”Kevin”, age:”27”]!
println person.name <- how you access the value

14. Groovy Features
• New for loop syntax
for(i in 1..5){!
println i!
}!
but Java loop syntax is supported anyways.

15. Groovy Features
Operator overloading
a + b (Java) becomes a.plus(b) (Groovy)
a++ or ++a (Java) becomes a.next() (Groovy)
switch(a) { case b: } becomes b.isCase(a)
More info: http://groovy.codehaus.org/Operator+Overloading

16. Groovy Features
• Switch statement is more general than Java, eg:
switch (val) {
case it > 3:
break
case 5..9:
break
case Number:
break
}

17. Groovy Features
• Groovy Truth
standard conditional operators on boolean
expressions
&
boolean expressions for collections (empty
collections = false)

18. Groovy Features
• Groovy Truth
Applies for Maps, iterations and enums, objects,
numbers
!
http://groovy.codehaus.org/Groovy+Truth

19. Groovy Features
• Closures : High Order Functions
Idea : Methods are like objects, anonymous class in steroids
Treated as a “code block” to be executed later, eg.
def testClosure = {
println “test closure”
}

20. Groovy Features
• Closures : High Order Functions
with parameters eg.
def methodName = { n, r ->
… do something
}
To call the method,
method(n, r)

21. Groovy Features
• File I/O
def count=0, MAXSIZE=100
new File("foo.txt").withReader { reader ->
while (reader.readLine() != null) {
if (++count > MAXSIZE) throw new RuntimeException('File too
large!')
}
}

22. Groovy Features
• File I/O
def fields = ["a":"1", "b":"2", "c":"3"]
new File("foo.ini").withWriter { out ->
fields.each() { key, value ->
out.writeLine("${key}=${value}")
}
}

23. More References
• Groovy http://groovy.codehaus.org
• Grails (www.grails.org) for Web development
• Griffon (www.griffon.org) for desktop app
development

24. Contacts
• http://gplus.to/kevintanhongann