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package

java.util

Classes | Description

Provides an extensive set of utility classes. more...

Interfaces

Collection<E> Collection is the root of the collection hierarchy. 
Comparator<T> Comparator is used to compare two objects to determine their ordering in respect to each other. 
Enumeration<E> An Enumeration is used to sequence over a collection of objects. 
EventListener EventListener is the superclass of all event listener interfaces. 
Formattable Any class that need to perform customer formatting by transferring converter specifier 's' to Formatter should implement the Formattable interface. 
Iterator<E> An Iterator is used to sequence over a collection of objects. 
List<E> List is a collection which maintains an ordering for its elements. 
ListIterator<E> An ListIterator is used to sequence over a List of objects. 
Map<K, V> Map has a set of keys, each key is mapped to a single value. 
Map.Entry<K, V> Map.Entry is a key/value mapping which is contained in a Map. 
Observer Observer must be implemented by objects which are added to an Observable. 
Queue<E> A kind of collection provides advanced operations than other basic collections, such as insertion, extraction, and inspection. 
RandomAccess RandomAccess is implemented by List implementations that support fast (usually constant time) random access. 
Set<E> Set is a collection which does not allow duplicate elements. 
SortedMap<K, V> SortedMap is a Map where the iterators sequence in order of the sorted keys. 
SortedSet<E> SortedSet is a Set which iterates its elements in sorted order. 

Classes

AbstractCollection<E> AbstractCollection is an abstract implementation of the Collection interface. 
AbstractList<E> AbstractList is an abstract implementation of the List interface, optimized for a backing store which supports random access. 
AbstractMap<K, V> AbstractMap is an abstract implementation of the Map interface. 
AbstractQueue<E> An abstract class which gives out skeletal implementations for some methods in Queue which include add, remove, and element that are based on offer, poll, and peek except that they throw exception to indicate the occurrence of some error instead of the return value of false or null. 
AbstractSequentialList<E> AbstractSequentialList is an abstract implementation of the List interface. 
AbstractSet<E> AbstractSet is an abstract implementation of the Set interface. 
ArrayList<E> ArrayList is an implementation of List, backed by an array. 
Arrays Arrays contains static methods which operate on arrays. 
BitSet The BitSet class implements a bit field. 
Calendar Calendar is an abstract class which provides the conversion between Dates and integer calendar fields, such as the month, year or minute. 
Collections Collections contains static methods which operate on Collection classes. 
Currency This class represents a currency as identified in the ISO 4217 currency codes. 
Date Date represents a specific moment in time, to the millisecond. 
Dictionary<K, V> Dictionary is a abstract class which is the superclass of all classes that associate keys with values, such as Hashtable. 
EnumMap<K extends Enum<K>, V>  
EnumSet<E extends Enum<E>>  
EventListenerProxy This abstract class provides a simple wrapper to types of EventListener. 
EventObject EventObjects represent events. 
FormattableFlags FormattableFlags are used as a parameter to method Formattable.formatTo() and instruct the output format in Formattables. 
Formatter

The Formatter class is a String-formatting utility that is designed to work like the printf function of the C programming language. 
GregorianCalendar GregorianCalendar provides the conversion between Dates and integer calendar fields, such as the month, year or minute, for the Gregorian calendar. 
HashMap<K, V> HashMap is an implementation of Map. 
HashSet<E> HashSet is an implementation of Set. 
Hashtable<K, V> Hashtable associates keys with values. 
IdentityHashMap<K, V> IdentityHashMap This is a variant on HashMap which tests equality by reference instead of by value. 
LinkedHashMap<K, V> LinkedHashMap is a variant on HashMap. 
LinkedHashSet<E> LinkedHashSet is a variant on HashSet. 
LinkedList<E> LinkedList is an implementation of List, backed by a linked list. 
ListResourceBundle ListResourceBundle is the abstract superclass of classes which provide resources by implementing the getContents() method to return the list of resources. 
Locale Locale represents a language/country/variant combination. 
Observable Observable is used to notify a group of Observer objects when a change occurs. 
PriorityQueue<E> PriorityQueue holds elements on a priority heap, which orders elements according to the comparator specified at construction or their natural order. 
Properties Properties is a Hashtable where the keys and values must be Strings. 
PropertyPermission PropertyPermission objects represent permission to access system properties. 
PropertyResourceBundle PropertyResourceBundle loads resources from an InputStream. 
Random This class provides methods that generates pseudo-random numbers of different types, such as int, long, double and float using either 
ResourceBundle ResourceBundle is an abstract class which is the superclass of classes which provide locale specific resources. 
Scanner A parser that parses a text string to primitive types with the help of regular expression. 
SimpleTimeZone SimpleTimeZone represents a local time zone and its daylight savings time rules for the gregorian calendar. 
Stack<E> Stack is a Last-In/First-Out(LIFO) data structure which represents a stack of objects. 
StringTokenizer String tokenizer is used to break a string apart into tokens. 
Timer Timers are used to schedule jobs for execution in a background process. 
TimerTask The TimerTask class is represents a task to run at specified time. 
TimeZone TimeZone is an abstract class which represents a local time zone and its daylight savings time rules. 
TreeMap<K, V> TreeMap is an implementation of SortedMap. 
TreeSet<E> TreeSet is an implementation of SortedSet. 
UUID

UUID is an immutable representation of a 128-bit universally unique identifier (UUID). 
Vector<E> Vector is a variable size contiguous indexable array of Objects. 
WeakHashMap<K, V> WeakHashMap is an implementation of Map with keys which are WeakReferences. 

Enums

Formatter.BigDecimalLayoutForm The enumeration giving the available styles for formatting very large decimal numbers. 

Exceptions

ConcurrentModificationException This runtime exception is thrown when a Collection is modified and an existing iterator on the Collection is used to modify the Collection as well. 
DuplicateFormatFlagsException The unchecked exception will be thrown out if there are duplicate flags given out in the format specifier. 
EmptyStackException Runtime exception which is thrown when pop/peek method of stack is executed on a stack which is empty  
FormatFlagsConversionMismatchException The unchecked exception will be thrown out if a conversion and flags are incompatible. 
FormatterClosedException The unchecked exception will be thrown out if the formatter has been closed. 
IllegalFormatCodePointException The unchecked exception will be thrown out if an invalid Unicode code point, which is Character.isValidCodePoint(int), is passed as a parameter to Formatter. 
IllegalFormatConversionException The unchecked exception will be thrown out when the parameter is incompatible with the corresponding format specifier. 
IllegalFormatException Unchecked Exception that is to be thrown out when a format string that contains either an illegal syntax or format specifier is transferred as a parameter. 
IllegalFormatFlagsException The unchecked exception will be thrown out if the combination of the format flags is illegal. 
IllegalFormatPrecisionException The unchecked exception will be thrown out when the precision is a negative other than -1, or the conversion does not support a precision or other cases when the precision is not supported. 
IllegalFormatWidthException The unchecked exception will be thrown out when the width is a negative other than -1, or the conversion does not support a width or other cases when the width is not supported. 
InputMismatchException An InputMismatchException is thrown by a scanner to indicate that the next token does not match the pattern the specified type. 
InvalidPropertiesFormatException  
MissingFormatArgumentException The unchecked exception will be thrown out if there no corresponding argument with the specified conversion or an argument index that refers to a missing argument. 
MissingFormatWidthException The unchecked exception will be thrown out if the format width is missing but is required. 
MissingResourceException This runtime exception is thrown by ResourceBundle when a resouce bundle cannot be found or a resource is missing from a resource bundle. 
NoSuchElementException This runtime exception is thrown when trying to retrieve an element past the end of an Enumeration, or the first or last element from an empty Vector. 
TooManyListenersException This exception is thrown when an attempt is made to add more than one listener to an event source which only supports a single listener. 
UnknownFormatConversionException The unchecked exception will be thrown out if the format conversion is unknown. 
UnknownFormatFlagsException The unchecked exception will be thrown out if there is an unknown flag.