Groovy Cheatsheet
9807
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.
- Native syntax similar to Java
data-type variable-name = value;
- Using def keyword
def variable-name = value;
- 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