title: Java HashSet duplicates comparison
body: <p>I have a class <code>Person</code> which contains <code>String firstName, lastName</code>. I want to insert instances of this class into a <code>List</code>, but I don't want to insert duplicates.</p>
  
  <p>How do I use a <code>HashSet</code> such that it uses something like <code>firstName+lastName</code> to figure out duplicates?</p>