title: Sorting an ArrayList of Objects by field recursively
body: <p>I have a <code>Person</code> class with a constructor as such</p>
  
  <pre><code>Person(String name, String position, int birthYear)
  {
      this.name = name;
      this.position = position;
      this.birthYear = birthYear;
  }
  </code></pre>
  
  <p>I also have a <code>Work</code> class that has an <code>ArrayList&lt;Person&gt; personnel</code> that I need to sort recursively by <code>birthYear</code>.  I am at a complete and total loss as to how to do this.  The solution I need, by the assignment, cannot include interfaces.  I know how to sort integer arrays, but I'm not sure how when there is an ArrayList of objects involved.</p>