title: How Closures are executed?
body: <p>I'm very new to Groovy. I wonder how Closures are implemented in Groovy.</p>
  
  <p>Lets say :</p>
  
  <pre><code>def a = { println "Hello" }
  a()
  </code></pre>
  
  <p>when <code>a()</code> is done, what is actually happening behind the scenes? Which method does <code>a()</code> calls to make the closure executable? </p>
  
  <p>Thanks in advance.</p>