Bootstrap Add a background color to the active list

First Page
<!DOCTYPE html>
<html>
   <head>
      <title>Bootstrap Example</title>
      <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css">
      <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
      <script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
   </head>
   <body>
      <div class="container">
         <h2>Features of Java</h2>
         <div class="list-group">
            <a href="#" class="list-group-item active">Simple</a>
            <a href="#" class="list-group-item">Object-Oriented</a>
            <a href="#" class="list-group-item">Portable</a>
            <a href="#" class="list-group-item">Platform independent</a>
            <a href="#" class="list-group-item">Secured</a>
         </div>
      </div>
   </body>
</html>
Output

First Page