title: What does null mean?
body: <p>As I understood <code>null</code> is instance of <code>T</code> for all reference type <code>T</code>.</p>
  
  <p><strong>Question 1.</strong> What's defenition of <code>null</code>? How does <code>null</code> represents in memory?</p>
  
  <p>Consider the following case:
  We defined class</p>
  
  <pre><code>public class MyClass{
      Integer i;
  }
  </code></pre>
  
  <p>Now <code>null</code> can be cast to <code>MyClass</code>, but I don't explicitly define that.</p>
  
  <p><strong>Question 2.</strong> From what compiler will be know that <code>null</code> can be cast to <code>MyClass</code>?</p>