Groovy Introducation
Agenda
What is Groovy?
History of Groovy.
Why Groovy?
Setup Groovy
What do we mean by Dynamic typing in Groovy?
Closure in Groovy.
Comparison between Java and Groovy with examples.
What is GDK?
Strings in Groovy:
Multiline Strings.
GString.
Operator overloading in Groovy.
What is Groovy Truth?
Groovy Classes
Working with files.
What is Groovy
Groovy is an object-oriented programming language for the Java
platform. It is a dynamic language with features similar to those
of Python, Ruby, Perl, and Smalltalk. It can be used as a scripting
language for the Java Platform which provides Dynamic, Easy-to-use
and Integration capabilities to the Java Virutual Machine. It
absorbs most of the syntax from Java and it is much powerful in
terms of funtionalities which is manifiested in the form Closures,
Dynamic Typing etc.
History
Started by James Strachan and Bob McWhirter in 2003.
Guillaume Laforge and Jeremy Rainer took it forward.
Groovy 1.0 release in 2007.
Now in version 2.4
Why Groovy
Feels like Java, with no boilerplate code.
Dynamic.
Extends JDK.
Setup
Download the binary from http://groovy.codehaus.org
Install JDK > 1.5
Set GROOVY_HOME to point to the installation.
Add GROOVY_HOME/bin to the path variable.
SDKMAN! (The Software Development Kit Manager)
curl -s get.sdkman.io | bash
source "$HOME/.sdkman/bin/sdkman-init.sh"
sdk install groovy
groovy -version
Groovy Shell
Open a terminal window and type groovysh. It allows easy access
to evaluate Groovy expressions, and run simple experiments.
Dynamic Typing Vs Static Typing
First, dynamically-typed languages perform type checking at
runtime, while statically typed languages perform type checking at
compile time.
This means that scripts written in dynamically-typed languages
(like Groovy) can compile even if they contain errors that will
prevent the script from running properly (if at all). If a script
written in a statically-typed language (such as Java) contains
errors, it will fail to compile until the errors have been
fixed.
// Java example
int num;
num = 5;
// Groovy example
num = 5
Groovy is dynamically-typed and determines its variables' data
types based on their values, so this line is not required.
Closures
A Closure is a block of code given a name.
Groovy has support for closures, which work much like Java 8
lambdas. A closure is an anonymous block of executable code
Methods can accept closure as parameters.
def helloWorld = {
println "Hello World"
}
Helloworld()
With Parameters
def power = { int x, int y ->
return Math.pow(x, y)
}
println power(2, 3)
Type definition of parameters is the same like variables. If you
define a type you can only use this type, but you can also skip the
type of parameters and pass in anything you want
def say = { what ->
println what
}
say "Hello World"
Passing Closure
The power of being able to assign closures to variable is that
you can also pass them around to methods.
def transform = { str, transformation ->
transformation(str)
}
println transform("Hello World", { it.toUpperCase() })
Java to Groovy
public class Demo{ public static void main(String[] args) {
for(int i = 0; i < 3; i++) { System.out.print("shipra" ); }
}}
Java to Groovy
3.times { print 'Nexthoughts' }
GDK
Enhancement over JDK.
The GDK sits on top of the JDK
Provides new Libraries and APIs to Groovy Developer.
Strings
In groovy , a string can be defined three different ways :using
double quotes, single quotes, or slashes (calledslashy strings).
def helloChris = "Hello" def helloJoseph = 'Hello, World' def
helloJim = /Hello, World/
MultiLine String
A multiline string is defined by using three double quotes or
three single quotes.
Multiline string support is very useful for creating templates
or embedded documents (such as XML templates, HTML, and so on).
def multiLineString = """ Hello, This is a multiline string
...... """
GString
A GString is just like a normal string, except that it evaluates
expressions that are embedded within the string,in the form
${...}.
def name = "Jim" def helloName = "Hello, ${name}" println
helloName // Hello, Jim println helloName.class.name
//org.codehaus.groovy.runtime.GStringImpl
Operator Overloading
Groovy supports operator overloading which makes working with
Numbers, Collections, Maps and various other data structures easier
to use.def date = new Date()date++println date
All operators in Groovy are method calls.
The following few of the operators supported in Groovy and the
methods they map toa + b a.plus(b)a - b a.minus(b)a * b
a.multiply(b)a ** b a.power(b)a / b a.div(b)a % b a.mod(b)
Groovy Truth
In Groovy you can use objects in if and while expressions.
A non-null and non-empty string will evaluate to true. If("John"
) // any non-empty string is true if(null) // null is false if("" )
// empty strings are false
Non zero numbers will evaluate to true. If(1) // any non-zero
value is true If(-1) // any non-zero value is true If(0) // zero
value is false
Groovy Truth For Collection
A non-empty collection will evaluate to true.List family =
["John" , "Jane" ]if(family) // true since the list is
populated.
And Empty Collection will evaluate to falseList family = [
]if(family) // false since the map is not populated.
Groovy Classes
In Groovy Classes by default things are public unless you
specify otherwise. Class Person { String name Integer age }
Person person = new Person() person.name = Per person.age
=30
If you call person.name=Groovy
Then behind the scene
person.setName(Groovy) If you want accidental modification in
Groovy, you can add a pair of getters and setters.
Constructors
Person person = new Person(name:Groovy, age:20) Person x = new
Person()
Working with Files
new File("foo.txt").bytesnew File("foo.txt").readLines()new
File("foo.txt").eachLine { line -> println(line) }
Thank You
More information please contact at [email protected]
