Enumeration: This method for enumerating sets of values.
Observer: This method for enabling classes to be observable objects.
BitSet: It is a set of bits.
Date: The current system date, as well as methods for generating and parsing dates.
Dictionary: It is an abstract class that maps between keys and values.
Hashtable: It is a hash table.
Observable: It is an abstract class for observable objects.
Properties: It is a hash table that contains behaviour for setting and retrieving persistent properties of the system.
Random: Utilities for generating random numbers.
Stack: It follows the last-in-first-out order.
StringTokenizer: Utilities for splitting strings into individual “token“.
Vector: It is a growable array of objects.