Introduction to Groovy

Groovy Language

• Groovy can run on JVM
• Groovy scripts can be executed using groovy jar file.
• Annotations are supported in groovy.

Groovy installation.

• Binary download link http://www.groovy-lang.org/download.html
• The binary can be run from command prompt
• Set GROOVY_HOME, GROOVY_HOME\bin variable as enviroment variable.
• After installing and running in the command line you get the groovy shell(groovysh).
• groovy> println ” hello helical”

Source code in groovy.

• The extension for groovy source file is .groovy
• We can write either script or we may also encapsulate the code as class definition inside this file.
• By default groovy class is subclassed by java.lang.Object.
• Java class and its objects can access groovy script class and object and vice versa.
• Using groovyc we can compile the source code.
• Plain Old Groovy Objects (POGO).

Intersting facts about groovy.

• Groovy doesnot require ; at the end of statement.
• Last expression of the method is returned by default. So we may not explicitly use return keyword.
• Maps, list and regular expression readily available in groovy.
• The following package are readily available. (groovy.lang.*, groovy.util.* , java.lang.*, j ava.util.*, java.net.*, java.io.*, java.math.BigInteger, java.math.BigDecimal)
• Its classes and methods are by-default public
• Automatic getter and setter is created for the fields in groovy class.
• Unlike java == operator in groovy checks for contents.
• The is() may be used to check if two variables/object refer the same.
• The parameters inside a function are optional.
• Gpath is expression language to evaluate nested structure.

Data types in Groovy.

• • The keyword def is used to define variable. We can also use specific type for variable declaration. Example int marks, String company. etc
  • Range data type is a Collection. Ranges consists of two values separated by two dots.

for (i in 0..9) {
  println ("Hello $i")
}

assert 'L'..'P' == ['L', 'M', 'N', 'O','P']

String & Gstring.

• ‘Strings may be enclosed inside single quote ‘.
• “Mehod() calls and ${variable} substitution inside a string is known as Gstring”.
• ”’Tripple single quotes can be used for multi line string”’
• “”” Multi line Gstring can be enclosed in tripple quotes”””
• /regularexpression/

Methods in Groovy.

• Groovy supports operator overloading. – operator can be used to substract string, << can be used for string concatination.
• Groovy string has .toUrl() method that can be directly used to convert a string to Url encoding string.

package packageName
class ClassName {
  static void main(def args){
    def hetroList= [1,2,"hi","45"]
    hetroList.each{ println it }
  }
} 

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