docs: private boolean isEqual(Object o1, Object o2)
      {
          // Both null - they are equal
          if (o1 == null && o2 == null)
          {
              return true;
          }
          // One is null and the other isn't - they are not equal
          if ((o1 == null && o2 != null) || (o1 != null && o2 == null))
          {
              return false;
          }
  
          // Otherwise fight it out amongst themselves
          return o1.equals(o2);
      }