"Groovy is like a super version of Java. It can leverage Java's enterprise capabilities but also has cool productivity features like closures, builders and dynamic typing. If you are a developer, tester or script guru, you have to love Groovy."

Samples

A simple hello world script:

def name='World'; println "Hello $name!"

A more sophisticated version using Object Orientation:

class Greet {
  def name
  Greet(who) { name = who[0].toUpperCase() +
                      who[1..-1] }
  def salute() { println "Hello $name!" }
}

g = new Greet('world') // オブジェクトを作成
g.salute()             // "Hello World!" を出力

Leveraging existing Java libraries:

import static org.apache.commons.lang.WordUtils.*

class Greeter extends Greet {
  Greeter(who) { name = capitalize(who) }
}

new Greeter('world').salute()

On the command line:

groovy -e "println 'Hello ' + args[0]" World

Getting Started Guide
How to install and begin using Groovy as well as introductory tutorials.

User Guide
Provides information about using the Groovy language including language facilities, libraries and programming guidelines.

Cookbook Examples
Illustrates larger examples of using Groovy in the Wild with a focus on applications or tasks rather than just showing off the features, APIs or modules.

Developer Guide
Contains information mainly of interest to the developers involved in creating Groovy and its supporting modules and tools.

Testing Guide
Contains information of relevance to those writing developer tests or systems and acceptance tests.

Advanced Usage Guide
Covers topics which you don't need to worry about initially when using Groovy but may want to dive into to as you strive for Guru status.