Package java.util

Contains the collections framework, legacy collection classes, event model, date and time facilities, internationalization, and miscellaneous utility classes (a string tokenizer, a random-number generator, and a bit array).

See: Description

Interface Summary

Interface	Description
Collection	The root interface in the collection hierarchy.
Comparator	A comparison function, which imposes a total ordering on some collection of objects.
Enumeration	An object that implements the Enumeration interface generates a series of elements, one at a time.
EventListener	A tagging interface that all event listener interfaces must extend.
Iterator	An iterator over a collection.
List	An ordered collection (also known as a sequence).
ListIterator	An iterator for lists that allows the programmer to traverse the list in either direction, modify the list during iteration, and obtain the iterator's current position in the list.
Map	An object that maps keys to values.
Map.Entry	A map entry (key-value pair).
Observer	A class can implement the Observer interface when it wants to be informed of changes in observable objects.
RandomAccess	Marker interface used by List implementations to indicate that they support fast (generally constant time) random access.
Set	A collection that contains no duplicate elements.
SortedMap	A map that further guarantees that it will be in ascending key order, sorted according to the natural ordering of its keys (see the Comparable interface), or by a comparator provided at sorted map creation time.
SortedSet	A set that further guarantees that its iterator will traverse the set in ascending element order, sorted according to the natural ordering of its elements (see Comparable), or by a Comparator provided at sorted set creation time.

Class Summary

Class	Description
AbstractCollection	This class provides a skeletal implementation of the Collection interface, to minimize the effort required to implement this interface.
AbstractList	This class provides a skeletal implementation of the List interface to minimize the effort required to implement this interface backed by a "random access" data store (such as an array).
AbstractMap	This class provides a skeletal implementation of the Map interface, to minimize the effort required to implement this interface.
AbstractSequentialList	This class provides a skeletal implementation of the List interface to minimize the effort required to implement this interface backed by a "sequential access" data store (such as a linked list).
AbstractSet	This class provides a skeletal implementation of the Set interface to minimize the effort required to implement this interface.
ArrayList	Resizable-array implementation of the List interface.
Arrays	This class contains various methods for manipulating arrays (such as sorting and searching).
BitSet	This class implements a vector of bits that grows as needed.
Calendar	Calendar is an abstract base class for converting between a Date object and a set of integer fields such as YEAR, MONTH, DAY, HOUR, and so on.
Collections	This class consists exclusively of static methods that operate on or return collections.
Currency	Represents a currency.
Date	The class Date represents a specific instant in time, with millisecond precision.
Dictionary	The Dictionary class is the abstract parent of any class, such as Hashtable, which maps keys to values.
EventListenerProxy	An abstract wrapper class for an EventListener class which associates a set of additional parameters with the listener.
EventObject	The root class from which all event state objects shall be derived.
GregorianCalendar	GregorianCalendar is a concrete subclass of Calendar and provides the standard calendar used by most of the world.
HashMap	Hash table based implementation of the Map interface.
HashSet	This class implements the Set interface, backed by a hash table (actually a HashMap instance).
Hashtable	This class implements a hashtable, which maps keys to values.
IdentityHashMap	This class implements the Map interface with a hash table, using reference-equality in place of object-equality when comparing keys (and values).
LinkedHashMap	Hash table and linked list implementation of the Map interface, with predictable iteration order.
LinkedHashSet	Hash table and linked list implementation of the Set interface, with predictable iteration order.
LinkedList	Linked list implementation of the List interface.
ListResourceBundle	ListResourceBundle is an abstract subclass of ResourceBundle that manages resources for a locale in a convenient and easy to use list.
Locale	A Locale object represents a specific geographical, political, or cultural region.
Observable	This class represents an observable object, or "data" in the model-view paradigm.
Properties	The Properties class represents a persistent set of properties.
PropertyPermission	This class is for property permissions.
PropertyResourceBundle	PropertyResourceBundle is a concrete subclass of ResourceBundle that manages resources for a locale using a set of static strings from a property file.
Random	An instance of this class is used to generate a stream of pseudorandom numbers.
ResourceBundle	Resource bundles contain locale-specific objects.
SimpleTimeZone	SimpleTimeZone is a concrete subclass of TimeZone that represents a time zone for use with a Gregorian calendar.
Stack	The Stack class represents a last-in-first-out (LIFO) stack of objects.
StringTokenizer	The string tokenizer class allows an application to break a string into tokens.
Timer	A facility for threads to schedule tasks for future execution in a background thread.
TimerTask	A task that can be scheduled for one-time or repeated execution by a Timer.
TimeZone	TimeZone represents a time zone offset, and also figures out daylight savings.
TreeMap	Red-Black tree based implementation of the SortedMap interface.
TreeSet	This class implements the Set interface, backed by a TreeMap instance.
Vector	The Vector class implements a growable array of objects.
WeakHashMap	A hashtable-based Map implementation with weak keys.

Exception Summary

Exception	Description
ConcurrentModificationException	This exception may be thrown by methods that have detected concurrent modification of an object when such modification is not permissible.
EmptyStackException	Thrown by methods in the Stack class to indicate that the stack is empty.
MissingResourceException	Signals that a resource is missing.
NoSuchElementException	Thrown by the nextElement method of an Enumeration to indicate that there are no more elements in the enumeration.
TooManyListenersException	The TooManyListenersException Exception is used as part of the Java Event model to annotate and implement a unicast special case of a multicast Event Source.

Package java.util Description

Contains the collections framework, legacy collection classes, event model, date and time facilities, internationalization, and miscellaneous utility classes (a string tokenizer, a random-number generator, and a bit array).

Package Specification

• Collections Framework Overview
• Collections Framework Annotated Outline

Related Documentation

For overviews, tutorials, examples, guides, and tool documentation, please see:

• Collections Framework Tutorial
• Collections Framework Design FAQ

Since:

JDK1.0