hashCode method
overriding, 352–354
for rental object, 352–353
HashSet object, 151
HashSet transactional field, 145
hasSubclasses method (Extent interface), 40
Heffalump example class, 26–28
help command, 283, 291
Helpers, 227–234
Hierarchy
derived class in, 229
for JDO exceptions, 255
Hollow object
refreshing, 95
retrieving, 92
Hollow state, 19, 21
HTTP protocol, 332
HttpServletRequest object, 342
HttpSession objects, 332, 335, 339, 344, 354
HttpSessionActivationListener interface, 354
HttpSessionBindingListener interface, 354