title: Clear activity from stack from another activity
body: <p>I have starting screen,which is my first activity in my application.</p>
  
  <p>This activivty contains only one button and when its clicked, it should navigate to another activity which should prompt user for name.</p>
  
  <p>If user press back button before confirming name, it should navigate back to the previous activity. </p>
  
  <p>But when user confirm name, main activity should pop up and foregone activities should be removed from application.</p>
  
  <p>I was looking for a solution and find it in creating static activity object , but i saw it was not wise and it is bad for memory.</p>
  
  <p>What is the best approach for doing what i explained?</p>