title: Why Android Studio has this @Nullable thing?
body: <p>I am just kind of curious about this weird thing that Android Studio is showing me. I was about to use the <code>addView</code> method when this tool-tip-like thingy pops up:</p>
  
  <p><a href="https://i.stack.imgur.com/n7MTF.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/n7MTF.png" alt="enter image description here"></a></p>
  
  <p>I am quite confused because of the <code>@Nullable</code> annotations on the parameters. <code>View</code> can be null because it is a reference type. But why an explicit <code>@Nullable</code> annotation?</p>
  
  <p>When I go into the definition of the <code>addView</code> method, I see no annotations! Then I am more confused.</p>
  
  <p>So I want to ask why Android Studio has this weird thingy.</p>