Groovy tutorial with examples

 
def map = [:]
 

 
def str= new StringBuffer()
map.each{ str << it.key +':'+ it.value +', '}
println str.toString()
 

 
println [:].isEmpty()  // true
println map.isEmpty()  // false
println map.containsKey(2) // true
println map.containsValue('b') // true
println map.containsValue('z') // false
 
// clear
map.clear()
println map
 
// group a list into a map using some criteria
def map2 =[1:'a', 7:'b', 6:'b', 3:'c']
println map2.groupBy{ it.key }
println map2.groupBy{ it.value }
 

 
package com.java.connect.groovy
 
class GroovyListEachExample {
    static void main(args){
        def list1 = ['Window', 'Linux', 'Mac']
        def list2 = [
            'java',
            'C',
            'C++',
            '.Net',
            'PHP',
            'Testing'
        ]
 
        list1.each {platform->
            list2.each {language-> println "Learning $language on $platform OS."  }
            println "----------------------------------"
        }
    }
}
 
//output
 
Learning java on Window OS.
Learning C on Window OS.
Learning C++ on Window OS.
Learning .Net on Window OS.
Learning PHP on Window OS.
Learning Testing on Window OS.
----------------------------------
Learning java on Linux OS.
Learning C on Linux OS.
Learning C++ on Linux OS.
Learning .Net on Linux OS.
Learning PHP on Linux OS.
Learning Testing on Linux OS.
----------------------------------
Learning java on Mac OS.
Learning C on Mac OS.
Learning C++ on Mac OS.
Learning .Net on Mac OS.
Learning PHP on Mac OS.
Learning Testing on Mac OS.
----------------------------------
 

 
 
 
//create a new list 
 
def emptyList = []
def list = [1, 2, 3, 4, 5, 6]
 
println emptyList.size() // This will give 0
println list.size() // This will give 6
 
You can add other list by ‘+’ operator.
 
// You can add other list by '+' operator
list = list + [7, 8]
println list // Gives as [1, 2, 3, 4, 5, 6, 7, 8]
 
//As well you can minus some elements by ‘-‘ operator.
 
list = list - [1]
println list // Gives as [2, 3, 4, 5, 6, 7, 8]
 
//add more elements into list by ‘<<' operator.
 
list = list << 9
println list // Gives as [2, 3, 4, 5, 6, 7, 8, 9]
 
//You can multiply the list by ‘*’ operator. The ‘*’ operator will repeat the list by given times.
 
list = list*2 // or list.multiply(2)
println list // Gives as [2, 3, 4, 5, 6, 7, 8, 9, 2, 3, 4, 5, 6, 7, 8, 9]
 
//make a flat list of elements 
 
assert [1, 2, [3, 4]].flatten() == [1, 2, 3, 4]
 
//You can reverse the list using reverse() method
 
 
def list1 = [1, 2, 3, 4]
list1 = list1.reverse()
println list1 // Gives as [4, 3, 2, 1]
 
//You can get the number of unique elements in list.
 
def list1 = [1, 2, 3, 4, 2]
list1 = list1.unique()
println list1 // Gives as [1, 2, 3, 4]
 
//You can sort the elements of list.
 
def list1 = [2, 2, 1, 4, 3]
list1 = list1.sort()
println list1 // Gives as [1, 2, 2, 3, 4]
 
//You can search the elements or collect the list of elements using find or findAll method as below.
 
def list1 = [2, 2, 1, 4, 3]
list1 = list1.find{it ==1}
println list1 // Gives as 1
 
//Or
 
def list1 = [2, 2, 1, 4, 3]
list1 = list1.findAll{it >1}
println list1 // Gives as [2, 2, 4, 3]
 
//You can iterate elements of list using ‘each’ method.
 
def list1 = [2, 2, 1, 4, 3]
list1 = list1.each {
  println it 
}
 
 

 
 
 
 
Date date = new Date()
 
//Groovy also can make use of third party java date library like Joda.
 
//Groovy has the special support for changing time like this.
 
Date date = new Date()
println(date)
use(TimeCategory) {
        Date date2 = date + 1.week + 6.hours
    println(date2)
}
 
// full code
 
 
import static java.util.Calendar.getInstance as now
import groovy.time.TimeCategory
 
import java.text.SimpleDateFormat
 
class GroovyDateExample {
    static void main(def args) {
        // get the current time
        println("Current time is "+now().time)
 
        // You can add the number of days in date like this
        def date1 = new Date() + 1
        println("Tomorrow’s 's date " +date1)
 
        //Get the date
        Date date = new Date()
        println(date)
        use(TimeCategory) {
            Date date2 = date + 1.week + 6.hours
            println("Date after adding 1 week and 6 hours is "+date2)
        }
 
        def input = "12-12-1981"
        def df1 = new SimpleDateFormat("dd-MM-yyyy")
        def date3 = df1.parse(input)
        def df2 = new SimpleDateFormat("MMM/dd/yyyy")
        println('The Original date was ' + df2.format(date3))
 
 
    }
}
 
//output
 
Current time is Sun Jul 10 11:30:13 GMT 2021
Tomorrow’s date Mon Jul 11 11:30:13 GMT 2021
Sun Jul 10 11:30:13 GMT 2021
Date after adding 1 week and 6 hours is Sun Jul 17 17:30:13 GMT 2021
The Original date was Dec/12/1981
 
 
 

 
 
class GroovyNumberExample {
 
    static void main(def args) {
 
        def x = 5
        def y = 6
        // You can do normal add
        println(x + y)
        // This is also allowed
        println(x.plus(y))
        // You can check the x in what instance
        println(x instanceof Integer)
 
        // Take the other example
        def a = 5/6
        // Get round value
        def b = a.setScale(4, BigDecimal.ROUND_HALF_UP)
        println(b.toString())
 
        // Add by operator
        println(7+8)
        // Add by method
        println(7.plus(7))
        // Minus by operator
        println(7-6)
        // Minus by method
        println(7.minus(6))
        // Multiply by operator
        println(4*12)
        // Multiply by method
        println(4.multiply(12))
        // mod by operator
        println(45%35)
        // mod by method
        println(45.mod(35))
        // Power by operator
        println(4**2)
        //Power by method
        println(4.power(2))
        //Division by operator
        println(4/3)
        // Division by method
        println(4.div(3))
        // Normal integer division
        println(4.intdiv(3))
 
    }
}
 

 
class GroovyStringExample {
    static void main(def args){
        // Single quotes string
        def name = 'Sam'
        def lastname = 'Crow'
 
        println name + ' ' + lastname
        // Double quotes string with variables evaluations
        def text = " My full name is $name $lastname"
        println(text)
 
        // You can get by indexing indexing 
        assert fullname[0..7] == name
        assert fullname[-4..-1] == lastname
 
        // Multi-line strings
        def sentance = '''\
        This is line 1, 
        This is line 2'''
        def lines =sentance.split('\n')
        assert lines.size() == 2
 
       // substrings example
       def string = 'My name is spiderman'
       string = string-'name'-'is' - 'My' + ' gone'
       println(string)
       // Replacement
       println(string.replace('gone','back'))
 
       //You can process the each chars of the String in Groovy, There are different way to do this, below is the example of some of char processing.
 
       // You can process characters as well
       assert 'spiderman'.toList() == [
           's',
           'p',
           'i',
           'd',
           'e',
           'r',
           'm',
           'a',
           'n'
       ]
       //You also can do like this and process the each char inside string
       'spiderman' as String[]
       'spiderman'.split('')
       'spiderman'.each{}
        
        
       string = "spiderman is back"
       println(string.toList().unique().sort().join())
    }
}