title: Unknown variable in class in Java
body: <p>I think it's stupid but I must know what that thing is (in the red circle), is it a variable or something? This is tutorial from YouTube (<a href="https://www.youtube.com/watch?v=lF5m4o_CuNg" rel="nofollow noreferrer">https://www.youtube.com/watch?v=lF5m4o_CuNg</a>).</p>
  
  <p>I want to learn some about this but when I don't even know name of that I can't search info about this.</p>
  
  <p><img src="https://i.stack.imgur.com/mstFc.png" alt="enter image description here"></p>