Groovy

 Groovy is not strict type script like java.

 Groovy is case-sensitive 

Variable 
     def principal=2000;

     println "principal : $principal or ${principal} or "+principal 

     def amount = 1000 + principal

     println "amount : $amount"

      Variable can be referred in String as $principal or ${principal}

      Variable will be referred by its name as well

Function

    def doubleIt(n) {

        n + n // Note we don't need a return statement

    } 

  

    foo = 5

    println "doubleIt($foo) = "+doubleIt(foo)

   foo = "foobar"

   println "doubleIt($foo) = ${doubleIt(foo)}"

   Function can be referred in String as ${doubleIt(foo)}

   Function can be referred outside of string as doubleIt(foo)

Closure

Is is different way of declaring the functions . They also capture variables from there enclosing environment.. Closure can be passed around to a different variable. 

https://groovy-lang.org/closures.html

def foo ="One million dollars"

def myClosure = {

  println "Hello from a closure"

  println "The value of foo is $foo"

}

myClosure()

        or

def bar = myClosure

def baz = bar

baz()

In closure the arguments are present on the left side of the arrow with comma separated .

We can pass closure as parameter to a function. 

def double_It = {x -> x+x }

def sum_It = {x,y -> x+y}

 

def number1 =5 

def number2 =10

def result= double_It 5

println "result is $result"

result = sum_It 5,10

println "result is $result"

def applyTwice(func,arg){

func(func(arg))

}

def doubledtwice = applyTwice(double_It,number1)

println "Applying doubelit twice to $number1 equals $doubledtwice"

https://www.infoworld.com/article/2073966/groovy-scripts-master-their-own-classpath-with-rootloader.html