title: Group By Java 8
body: <p>Assume you an Student enrolling to courses</p>
  
  <pre><code>Class Student{
    ArrayList&lt;Course&gt; courses;
  }
  Class Course{
    String id;
    String name;
  }
  </code></pre>
  
  <p>How can use groupBy function with java 8 to list of students attending a particular course</p>