title: How to use auto increment for an object type in android?
body: <p>Okay, I am saving files in a json file which which unlike a db that has an auto-increment function.</p>
  
  <p>Say I have this object.</p>
  
  <pre><code>public book() {
  id = ?????
  Title = mTitle;
  }
  </code></pre>
  
  <p>How can you make the id to give you an unique int number? is that possible? Thanks in advance.</p>