Java Reference
In-Depth Information
Summary
TheCollectionsFrameworkisastandardarchitectureforrepresentingandmanipulating
collections,whicharegroupsofobjectsstoredininstancesofclassesdesignedforthis
purpose.Thisframeworklargelyconsistsofcoreinterfaces,implementationclasses,and
utility classes.
Thecoreinterfacesmakeitpossibletomanipulatecollectionsindependentlyoftheir
implementations.Theyinclude Iterable , Collection , List , Set , SortedSet ,
NavigableSet , Queue , Deque , Map , SortedMap ,and NavigableMap . Col-
lection extends Iterable ; List , Set , and Queue each extend Collection ;
SortedSet extends Set ; NavigableSet extends SortedSet ; Deque extends
Queue ; SortedMap extends Map ; and NavigableMap extends SortedMap .
The framework's implementation classes include ArrayList , LinkedList ,
TreeSet , HashSet , LinkedHashSet , EnumSet , PriorityQueue , Ar-
rayDeque , TreeMap , HashMap , LinkedHashMap , IdentityHashMap ,
WeakHashMap ,and EnumMap .Thenameofeachconcreteclassendsinacoreinter-
face name, identifying the core interface on which it is based.
Theframework's implementation classes alsoinclude theabstract AbstractCol-
lection , AbstractList , AbstractSequentialList , AbstractSet , Ab-
stractQueue ,and AbstractMap classes.Theseclassesofferskeletalimplementa-
tions of the core interfaces to facilitate the creation of concrete implementation classes.
The Collections Framework would not be complete without its Arrays and Col-
lections utility classes. Each class supplies various class methods that implement
useful algorithms in the contexts of arrays and collections.
Before Java 1.2's introduction of the Collections Framework, developers had two
choices where collections were concerned: create their own frameworks, or use the
Vector , Enumeration , Stack , Dictionary , Hashtable , Properties ,and
BitSet types, which were introduced by Java 1.0.
The Collections Framework has made Vector , Stack , Dictionary , and
Hashtable obsolete.Theframework's Iterator interfacehaslargelyobsoletedthe
Enumeration interface.ThePreferencesAPIhasmade Properties largelyobsol-
ete. Because BitSet is still relevant, this class continues to be improved.
Arrays,theCollectionsFramework,andlegacyclassessuchas BitSet aresuitable
fororganizinggroupsofobjects(or,inthecaseof BitSet ,setsofbitsthatareinter-
pretedasBooleantrue/falsevalues),andyoushouldusethemwhereverpossiblebefore
creating your own collection APIs.
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