code: public static String identityToString(Object o) {
          return o == null ? null : o.getClass().getName() + '@' + Integer.toHexString(System.identityHashCode(o));
      }
docs: Returns a string containing a concise, human-readable description of the
  object. The string is the same as the one that would be returned by
  Object.toString even if the object's class has overriden the toString
  or hashCode methods. The return value for a null object is null.
  
  @param o the object
  @return the string representation