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Catalog / Groovy Programming Language Cheatsheet

Groovy Programming Language Cheatsheet

A concise cheat sheet covering essential aspects of the Groovy programming language, including syntax, data types, collections, closures, and common operations. This cheat sheet is designed to provide a quick reference for developers working with Groovy, offering a practical overview of the language's core features and capabilities.

Groovy Basics and Syntax

Basic Syntax

Comments

// Single-line comment
/* ... */ Multi-line comment
/** ... */ Groovydoc comment

Statements

Statements do not necessarily need to end with a semicolon (;)

Variables

Declared with def, String, int, etc.
Groovy is dynamically typed, but static typing is also supported.

Strings

Single quotes ('...') for simple strings.
Double quotes ("...") for strings with variable interpolation.
Triple quotes ('''...''' or """...""") for multi-line strings.

Example

 
def name = "Groovy"
println "Hello, ${name}!" // Hello, Groovy!

Data Types

Primitive Types

int, long, float, double, boolean, char

Objects

Integer, Long, Float, Double, Boolean, Character, String

Collections

List, Set, Map

Ranges

1..10, 'a'..'z'

Operators

Arithmetic

+, -, *, /, %, ** (power)

Assignment

=, +=, -=, *=, /=, %=

Comparison

==, !=, <, >, <=, >=

Logical

&&, ||, !

Safe Navigation

?. (avoids NullPointerException)

Collections and Closures

Lists

Declaration

 
def list = [1, 2, 3]

Accessing Elements

 
println list[0] // 1

Adding Elements

 
list << 4
list.add(5)

Iterating

 
list.each { println it }

Maps

Declaration

 
def map = ['key1': 'value1', 'key2': 'value2']

Accessing Values

 
println map.key1 // value1
println map['key2'] // value2

Adding/Updating Values

 
map.key3 = 'value3'
map['key4'] = 'value4'

Iterating

 
map.each { key, value -> println "${key}: ${value}" }

Closures

Definition

 
def closure = { param -> println param }

Calling

 
closure('Hello') // Hello

Implicit Parameter

it (when the closure has only one parameter)

Example

 
def numbers = [1, 2, 3]
numbers.each { println it * 2 } // 2, 4, 6

Object-Oriented Programming

Classes

Definition

 
class Person {
 String name
 int age

 Person(String name, int age) {
 this.name = name
 this.age = age
 }
}

Creating Instances

 
def person = new Person('Alice', 30)
println person.name // Alice

Getters and Setters

Automatically generated for class properties.

Methods

Definition

 
class Calculator {
 def add(int a, int b) {
 return a + b
 }
}

Calling

 
def calc = new Calculator()
println calc.add(5, 3) // 8

Optional Parentheses

Parentheses can often be omitted.

println calc.add 5, 3 // 8

Traits (Interfaces with Implementation)

Definition

 
trait Loggable {
 def log(String message) {
 println "Logging: ${message}"
 }
}

Usage

 
class MyClass implements Loggable {
 def doSomething() {
 log('Doing something...')
 }
}

def obj = new MyClass()
obj.doSomething() // Logging: Doing something...

Working with Files and I/O

File Operations

Creating a File

 
def file = new File('example.txt')
file.createNewFile()

Writing to a File

 
file.write('Hello, Groovy!')

Reading from a File

 
def content = file.text
println content // Hello, Groovy!

Appending to a File

 
file << ' Appending text'
println file.text // Hello, Groovy! Appending text

Working with Streams

Reading from InputStream

 
def inputStream = new FileInputStream('example.txt')
inputStream.eachLine { println it }
inputStream.close()

Writing to OutputStream

 
def outputStream = new FileOutputStream('output.txt')
outputStream.write('Groovy Output'.getBytes())
outputStream.close()

Working with URLs

Reading Content from URL

 
def url = new URL('http://example.com')
def content = url.getText()
println content
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