he table where the friends list is
   * currently expanded.
   */
  private final Set&lt;Integer&gt; showingFriends = new HashSet&lt;Integer&gt;();

  /**
   * Column to control selection.
   */
  private Column&lt;ContactInfo, Boolean&gt; checkboxColumn;

  /**
   * Column to expand friends list.
   */
  private Column&lt;ContactInfo, String&gt; viewFriendsColumn;

  /**
   * Column displays first name.
   */
  private Column&lt;ContactInfo, String&gt; firstNameColumn;

  /**
   * Column displays last name