HelloWorld.groovy

 Map<String, Map<String, String>> map = [
  k1 : [k11 : 'v11'] ,
  k2 : [k11 : 'v21'] ,
  k3 : [k11 : 'v31']
]

def findValueBelongsTo( Map map, String keyword ) {
  map.findResult { k, v ->
    v instanceof Map
      ? v.containsValue(keyword) ? k : findValueBelongsTo( v, keyword )
      : null
  }
}

println findValueBelongsTo( map, 'v31')

created 4 years ago by marslo

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Read inputs from stdin

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def name = System.in.newReader().readLine()
println "Hello " + name

About Groovy

Groovy is an object-oriented programming language based on java. Apache Groovy is a dynamic and agile language which is similar to Python, Ruby, Smalltalk etc.

Key Features

It's not a replacement for java but it's an enhancer to Java with extra features like DSL support, dynamic typing, closures etc.
Accepts Java code as it extends JDK
Greater flexibility
Concise and much simpler compared to Java
Can be used as both programming language and scripting language.

Syntax help

Data Types

Data type	Description	Range
String	To represent text literals	NA
char	To represent single character literal	NA
int	To represent whole numbers	-2,147,483,648 to 2,147,483,647
short	To represent short numbers	-32,768 to 32,767
long	To represent long numbers	-9,223,372,036,854,775,808 to +9,223,372,036,854,775,807
double	To represent 64 bit floating point numbers	4.94065645841246544e-324d to 1.79769313486231570e+308d
float	To represent 32 bit floating point numbers	1.40129846432481707e-45 to 3.40282346638528860e+38
byte	To represent byte value	-128 to 127
boolean	To represent boolean values either true or false	True or False

Variables

You can define variables in two ways

Syntax:

data-type variable-name;

[or]

def variable-name;

Loops

0.upto(n) {println "$it"}

n.times{println "$it"}

where n is the number of loops and 0 specifies the starting index

Decision-Making

1. If / Nested-If / If-Else:

When ever you want to perform a set of operations based on a condition or set of conditions, then If / Nested-If / If-Else is used.

if(conditional-expression) {
  // code
} else {
  // code
}

2. Switch:

Switch is an alternative to If-Else-If ladder and to select one among many blocks of code.

switch(conditional-expression) {    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
...    
    
default:     
 //code to be executed when all the above cases are not matched;    
}

List

List allows you to store ordered collection of data values.

Example:

def mylist = [1,2,3,4,5];

List Methods	Description
size()	To find size of elements
sort()	To sort the elements
add()	To append new value at the end
contains()	Returns true if this List contains requested value.
get()	Returns the element of the list at the definite position
pop()	To remove the last item from the List
isEmpty()	Returns true if List contains no elements
minus()	This allows you to exclude few specified elements from the elements of the original
plus()	This allows you to add few specified elements to the elements of the original
remove()	To remove the element present at the specific position
reverse()	To reverse the elements of the original List and creates new list