An enumeratyion is an interface containing methods for accessing the accessing the underlying data struvture from which the enumeration is obtained. It is construct which collection classes return when you request a collection of all the objects stored in the collection. It allow sequential access to all the element stored in the collection. The vector classes provide the capability to implement a growable array of object. The set interference provide method for accessing the elements of a finite mathematical set. Sets to not allow duplicate elament.
The dictionary classes is the abstract super class of hanhtrable the properties classes Allow any object yhe abstract function used to store and retrieve object by key vbalue this classes allow any object to be used as akey orrr value. The hashtable class implements a hash table datas struvture. A hash to table dat struc ture and stores object in a dictionary using hash cioded afr integer value and identify object.

The properties class is a subclasses of hashtable that can be read from a wrootten to stream.
It also provides class the capability to specify a set of defult values to be used if a specified key is not found in the table. We have two method The resource bundle suvbclasses are used to store lacal spoec bt program to tailor the programs’s appreence to the particular lacals in whish it is beings run. Resource bundles provides t he capability to isolate a program locale specifies resource in a standard and modular manner.

Object that subclasses the observable class maintain list of observe. When an observable object is updated it invokes the update method of each of its observer that it has changed state . the observer interface is implemented bt objects that obsrever object
When an errors occurs within a method the method creates an object and hands it off to the its type and the state of the [rogram when the error occurred. Creting an excepi[tion object and handing it ti be runtime system is called throwing an exception.