Groovy - An extensible multi-paradigm language for the JVM Platform
(GroovyDoc for Groovy and Java classes)

Groovy...
  • is an extensible and multi-paradigm language for the Java Virtual Machine
  • makes modern programming features available to Java developers with almost-zero learning curve
  • has a dynamic nature like Python and Ruby, which means that it is very powerful, easy to learn, and productive
  • optionally has static typing like Java and Kotlin, which makes it fast and provides extra type checking when desired
  • has first-class functional, stream processing and immutability support, meaning that it offers features similar to Scala and can offer many advantages when working in parallel processing or clustered environments
  • supports Domain-Specific Languages and other compact syntax so your code becomes easy to read and maintain
  • makes writing shell and build scripts easy with its powerful processing primitives, OO abilities and an Ant DSL
  • increases developer productivity by reducing scaffolding code when developing web, GUI, database or console applications
  • simplifies testing by supporting unit testing and mocking out-of-the-box
  • compiles straight to Java bytecode so you can use it anywhere you can use Java; it seamlessly integrates with all existing Java objects and libraries
Packages 
Package Description
groovy.mock.interceptor  
groovy.test  
groovy.transform  
groovy.util  
org.apache.groovy.test  
org.apache.groovy.test.transform  
org.codehaus.groovy.runtime