package org.andromda.timetracker.vo;
   
   import java.util.Comparator;
   
   /**
    *
    */
   public class UserVOComparator implements Comparator<UserVO>
   {
      /**
       * Compares two UserVO objects based on their usernames. If the usernames are
       * not available (or null), it compares on id. <p>
       *
       * The comparison is null safe and places null objects less than non-null objects.<p>
       * @param o1
       * @param o2
       * @return result
       */
      @Override
      public int compare(UserVO o1, UserVO o2) {
          int result = 0; // assume equal
  
          if (o1 == null) {
              result = (o2 == null) ? 0 : -1;
          }
          else if (o2 == null) {
              result = 1;
          }
          else if ((o1.getUsername() != null) && (o2.getUsername() != null)) {
              // Both not-null, compare usernames
              result = o1.getUsername().compareTo(o2.getUsername());
          }
          else if ((o1.getId() != null) && (o2.getId() != null)) {
              // Both not-null but no names, check id's
              result = o1.getId().compareTo(o2.getId());
          }
  
          return result;
      }
  }