Chapter: Java The Complete Reference - The Java Library - java.util : The Collections Framework

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java.util : The Collections Framework

This chapter begins our examination of java.util. This important package contains a large assortment of classes and interfaces that support a broad range of functionality.

Chapter 18

java.util Part 1: The Collections  Framework

 

This chapter begins our examination of java.util. This important package contains a large assortment of classes and interfaces that support a broad range of functionality. For example, java.util has classes that generate pseudorandom numbers, manage date and time, observe events, manipulate sets of bits, tokenize strings, and handle formatted data. The java.util package also contains one of Java’s most powerful subsystems: the Collections Framework. The Collections Framework is a sophisticated hierarchy of interfaces and classes that provide state-of-the-art technology for managing groups of objects. It merits close attention by all programmers.

 

Because java.util contains a wide array of functionality, it is quite large. Here is a list of its top-level classes:

AbstractCollection

 

AbstractList

 

AbstractMap

 

AbstractQueue

 

AbstractSequentialList

 

AbstractSet

 

ArrayDeque

 

ArrayList

 

 

Arrays

 

Base64 (Added by JDK 8.)

 

 

BitSet

 

Calendar

FormattableFlags

 

Formatter

 

GregorianCalendar

 

HashMap

 

HashSet

 

Hashtable

 

IdentityHashMap

 

IntSummaryStatistics (Added by JDK 8.)

 

LinkedHashMap

 

LinkedHashSet

 

 

LinkedList

 

ListResourceBundle

 

Properties

 

PropertyPermission

 

PropertyResourceBundle

 

Random

 

ResourceBundle

 

Scanner

 

ServiceLoader

 

SimpleTimeZone

 

 

Spliterators (Added by JDK 8.)

 

SplitableRandom (Added by JDK 8.)

 

Stack

 

StringJoiner (Added by JDK 8.)

Collections

 

Currency

 

 

Date

 

Dictionary

 

DoubleSummaryStatistics

(Added by JDK 8.)

 

EnumMap

 

 

EnumSet

 

 

EventListenerProxy

 

 

EventObject

 

Locale

 

LongSummaryStatistics (Added by JDK 8.)

 

Objects

 

Observable

 

Optional (Added by JDK 8.)

 

OptionalDouble (Added by JDK 8.)

 

OptionalInt (Added by JDK 8.)

 

OptionalLong (Added by JDK 8.)

 

PriorityQueue

StringTokenizer

 

Timer

 

 

TimerTask

 

TimeZone

 

TreeMap

 

 

TreeSet

 

 

UUID

 

 

Vector

 

 

WeakHashMap

 

The interfaces defined by java.util are shown next:

 

Collection

 

Comparator

 

Deque

 

Enumeration

 

 

EventListener

 

 

Formattable

 

 

Iterator

 

 

List

 

 

ListIterator

 

Map

 

Map.Entry

 

NavigableMap

 

NavigableSet

 

Observer

 

 

PrimitiveIterator (Added by JDK 8.)

 

PrimitiveIterator.OfDouble (Added by JDK 8.)

 

PrimitiveIterator.OfInt (Added by JDK 8.)

 

PrimitiveIterator.OfLong (Added by JDK 8.)

 

Queue

 

RandomAccess

 

Set

 

SortedMap

 

SortedSet

 

Spliterator (Added by JDK 8.)

 

Spliterator.OfDouble (Added by JDK 8.)

 

Spliterator.OfInt (Added by JDK 8.)

 

Spliterator.OfLong (Added by JDK 8.)

 

Spliterator.OfPrimitive (Added by JDK 8.)

 

 

Because of its size, the description of java.util is broken into two chapters. This chapter examines those members of java.util that are part of the Collections Framework. Chapter 18 discusses its other classes and interfaces.

 


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