Groovy & Gradle: JVM Automation and Build Engineering · Lesson

Understanding Groovy Closures

Learn the concept of closures, how to define them, and their versatile applications in Groovy.

What Are Groovy Closures?

Welcome to the world of Groovy closures! A closure is essentially a block of code that can be treated like a variable.

Think of it as a mini-function you can define, store, and pass around. Closures are a powerful feature that make Groovy code very flexible and concise.

They are first-class citizens, meaning they can be assigned to variables, passed as arguments, and returned from methods.
They can capture variables from their surrounding scope, even after that scope has finished executing.

Basic Closure Syntax

Defining a closure is straightforward. You enclose your code block within curly braces {}. Let's see a simple example:

class Main {
  static void main(String[] args) {
    // Define a simple closure
    def sayHello = {
      println "Hello from a closure!"
    }

    // Call (execute) the closure
    sayHello()
  }
}

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