title: Firebase - Unique ID for every user
body: <p>I am building a firebase based android application which involves multiple user who authenticate and login to app. I want to provide a Unique to each users who authenticate&amp;login and which will not be changed even if user reinstall the application so that I can use and rely on that key to make a separate json branch for that specific user in database based on that id. </p>
  
  <p>I have searched the docs I found <code>user.getUid()</code> and <code>user.getToken()</code>. I am confused about these two which one will help me considering my situation.  </p>