title: What is the difference between null, 0 and nothing?
body: <p>What is the difference between <code>null</code>, <code>0</code> and <code>nothing</code>?</p>
  
  <p>I cannot find a question addressing all three of these.</p>
  
  <p>For example:</p>
  
  <p>If I am getting input from a <code>string</code> and parsing it to <code>int</code>.</p>
  
  <pre><code>return Integer.parseInt(sc.nextLine());
  </code></pre>
  
  <p>Or if I am asking if a <code>string != ""</code>, or a <code>is not nothing</code> I am confused about which to use when and why. </p>
  
  <p>I am confused about which one to use when validating data.</p>