groovy.md

title	description	created	updated
Groovy	Groovy cheatsheet contains useful code syntax with examples which is handy while coding.	2020-05-05	2020-05-05

Basics

Sample Program

println "Hello World!"

• println -- inbuilt library function which are used to display the output.
• // -- single line comment
• /* comments */ -- Multi line comment

Data types

Data type	Description	Example
int	used to represent whole numbers	int x = 99999
short	used to represent whole numbers	short x = 999
long	used to represent whole numbers	long x = 99999999999L
float	used to represent fractional numbers	float x = 22.79f
double	used to represent fractional numbers	double x = 99.99d
char	used to represent a single character	char grade = 'A'
boolean	used to represent Boolean data either true or false	boolean isAvailable = true
byte	Used to represent a byte value	byte x = 99
string	used to represent a series of characters	string msg = "Happy learning!"

Example

int int_var = 99999 // integer variable
short short_var = 999 // short variable
long long_var = 99999999999L // long variable
float float_var = 22.79f // float variable
double double_var = 99.99d // double variable
char char_var = 'A' // char variable
boolean isAvailable = true // boolean variable
byte byte_var  = 99 // byte variable
String msg = "Happy learning!" // String variable

Variables

There are three ways to declare variables in Groovy.

1. Native syntax similar to Java

data-type variable-name = value;

2. Using def keyword

def variable-name = value;

3. Variables in groovy do not require a type definition.

variable-name = value; // no type definition is required

Operators

Operator type	Description
Arithmetic Operators	+ , - , * , / , %
comparision Operators	< , > , <= , >=, != , ==
Bitwise Operators	& , ^ , |
Logical Operators	&& , ||, !
Assignment Operators	= , += , -= , *= , /= , %=

Strings

String string-var = value; 

value should be enclosed in either single quotes ’, double quotes “, or triple quotes “”” or forward slash / or dollar-forward slash $/.

String str = "Happy learning!"; 
String str2 = 'Hello World';
String str3 = """Hey
Good 
Morning"""

Lists

List is like stack which is used to store collection of data items.

def list1 = [ ] // empty list

def list2 = [ 1,2,3,4,5] // integer list

def list3 = ["Hello", "World"] //string list

def list4 = ["happy", 16] // list with different data

Methods

List methods	Description
add()	to append the new value to the end of this List.
contains()	Returns true if the list contains the given value.
get()	to get the element at the specified position from the List.
isEmpty()	Returns true if the given List is empty
minus()	to create a new List with the elements of the original list by removing those specified in the collection
plus()	to create a new List with the elements of the original list by adding those specified in the collection
pop()	to remove the last item from the List
remove()	to removes an element at the specified position in the List.
reverse()	to create a new List which is the reverse of the elements of the given List
size()	to get number of elements present in the List.
sort()	Returns a sorted copy of the given List.

Maps

A Map is an unordered collection of Key Value Pairs

def map1 = [‘Name’ : ‘OneCompiler’, ‘Category’ : ‘Learning’]
def map2 = [:] // empty map

Methods

Method name	Description
containsKey()	Used to check if a key is present in a given Map
get()	Looks for the key in the map and returns it's corresponding value.If there is no match then returns null
keySet()	to obtain set of keys in the given Map.
put()	used to associate the given value with the key specified in the Map. If already value is present for that key, then the old value gets replaced by the new value.
size()	Returns the number of key-value pairs present in the Map.
values()	Returns a collection view of the values present in the Map.

Conditional Statements

1. If

if(conditional-expression)
{
    //code
}

2. If-else

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

3. If-else-if ladder

if(conditional-expression-1)
{
    //code
} else if(conditional-expression-2) {
    //code
} else if(conditional-expression-3) {
    //code
}
....
else {
    //code
}

4. Nested-If

if(conditional-expression-1) {    
     //code    
          if(conditional-expression-2) {  
             //code
             if(conditional-expression-3) {
                 //code
             }  
    }    
}

5. Switch

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;    
} 

Loops

1. While

while(condition){  
//code 
}  

2. For

for(Initialization; Condition; Increment/decrement){  
//code  
} 

3. For..in

for (var in range) {
  //code
}

Groovy closures

{ [closureParameters -> ] statements }

Examples

{ x++ }         // only statement                                 

{ -> x++ }     // statement with no parameters                                  

{ name -> println name }  // statement with one closure parameter  with no type definition                         

{ String name, int id ->   // statement with two closure parameter has type definition                          
    println "hi ${name}, your id is ${id}" 
}

Groovy Closure Methods

Method name	Description
any() & every()	Iterates through each element of a collection checking whether given criteria is valid for at least one element.
find()	Finds the first value in a collection which matches the given criteria.
findAll()	Finds all values in a collection which matches the given criteria.
collect()	Iterates through a collection and converts each element into a new value using the closure as the transformer.

Method

Method is a sub-routine which contains set of statements which increases re-usuability and modularity.

def methodName(parameters) {  // defining a method
   //Method code 
}

methodName(parameters); // calling a method