title: Start with Java (JVM) ecosystem
body: <p>I have came from <a href="https://stackoverflow.com/questions/2992839/scala-java-or-clojure-java">another question</a> to this one:</p>
  
  <p>How can one start with Java (JVM) ecosystem? What are beginner, intermediate and advanced knowledge-bases (bags!)? To be honest Java ecosystem was always a bit confusing to me, so it would be very helpful to provide some "reference references" and "defacto tutorials" for learning (curve!) JVM.</p>
  
  <p>Note: I want to use JVM with Scala (or Clojure) but not Java itself.</p>
  
  <p>I am a C# developer (WPF, Windows Forms, ASP.NET, Web Services, ... like that).</p>