java unit 4 pdf - about java collections

AKTU syllabus java unit 4

1. CollectioninJava
Acollection inJava isaframeworkthatprovidesanarchitecturetostore
andmanipulate agroupofobjects.
JavaCollectionscanachieve alltheoperations thatyouperformondata
suchassearching,sorting,insertion,manipulation, anddeletion.
KeyPoints:
Collectionsareusedtostore,retrieve,manipulate,and
communicateaggregate data.
Collectionscanholdbothhomogeneousandheterogeneous data.
Theycandynamicallygrowandshrinkinsize.
CollectionFramework inJava
TheCollectionFrameworkprovidesaunifiedarchitecturefor
representingandmanipulating collections.
Allthecollectionsframeworkscontainthefollowing:
Interfaces:Theseareabstractdatatypesthatrepresent
collections.Theinterfacesallowcollectionstobemanipulated
independently ofthedetailsoftheirrepresentation.
1.Collection 3.Set 5.Map
2.List 4.Queue
Implementations:Thesearetheconcreteimplementations ofthe
collectioninterfaces.Essentially, theyarereusabledatastructures.
1ArrayList 3.Linkedlist 5.HashSet
2.TreeSet 4.HashMap 6.TreeMap
Algorithms:Thesearethemethodsthatperformuseful
computations,suchassearchingandsorting,onobjectsthat
Iteratorlnterface
TheIteratorinterfaceprovidesawaytoaccesselementsofacollection
sequentiallywithoutexposingtheunderlyingstructure.
Itispartofthejava.utilpackageandisauniversaliteratorforall
collections.
KeyPoints:
Methods:
booleanhasNext(): Returnstrueiftherearemore
elementstoiterateover.
Enext():Returnsthenextelementintheiteration.
voidremove():Removesthelastelementreturnedby
theiterator(optionaloperation).
t
Usage:
TheIteratorinterfaceisusedtotraversecollectionssuch
asList,Set,andMap.
Itsupportsbothreadandremoveoperations.
wArayListo):
List<String> list=new
list.add("A");
list.add("B");
list.add("C");
Iterator<String> iterator=list.iterator();
while(iterator.hasNext()
{
Stringelement=iterator. next();
System.out, printin(element);

2. computations, suchassearchingandsorting,onobjectsthat
implementcollectioninterfaces.
AdvantagesofCollectionFramework
Consistent API:Thecollectioninterfaceshaveabasicsetofoperations
(suchasaddingandremoving)thatareextendedbyall
implementations.
ReducesProgramming Effort:Byprovidingusefuldatastructuresand
algorithms,theCollectionsFrameworkreducestheprogrammingeffort.
JavaCollectionsFramework
TheJavaCollectionsFramework isstructuredasaunifiedarchitecture
forrepresentingandmanipulating collections.
Thehierarchy isbroadlydividedintothreemajorgroups:
List,Set,andQueue,whichextendtheCollectioninterface,
Map,which isaseparatehierarchy.
Herearetheimportantpointsforeachcomponent:
CollectionInterface
Therootinterfaceofthecollectionsframework.
CollectionInterface
TheCollectioninterface istherootofthecollectionhierarchy.
Itrepresents agroupofobjectsknownaselements.
TheCollectioninterface ispartofthejava.utilpackage.
KeyPoints:
Methods:
booleanadd(Ee):Ensuresthatthiscollectioncontains
thespecifiedelement.
booleanremove(Objecto):Removesasingleinstance
ofthespecifiedelementfromthiscollection.
intsize():Returnsthenumberofelementsinthis
collection.
booleanisEmpty():Returnstrueifthiscollection
containsnoelements.
booleancontains(0bject o):Returnstrueifthis
collectioncontainsthespecifiedelement.
Iterator<E> iterator(): Returnsaniteratoroverthe

3. Itprovidescommonmethodsikeadd(),remove(),
size(),clear(),contains(),anditerator()
MapInterface
Representsamappingbetweenakeyandavalue.
DoesnotextendtheCollectioninterface.
Providesmethodstoput,get,removeelementsbased
onakey.
Collection interface MapInterface
ashMap
Aryist nkedashMap
nkedList eeMap
ector t-Hashtabie
Stack
Hashset
nkedkashset
reeSet
PoortyQieae
+-DequeInterface
+-ArrayDeque
+-LinkedistDecue
elementsinthiscollection.
booleanaddAl|(Collection<? extendsE>c):Addsallof
theelementsinthespecifiedcollectiontothis
collection.
voidclear():Removes alloftheelementsfromthis
collection.
Subinterfaces:
1.List 2.Set 3.Queue
Usage:
TheCollectioninterfaceprovidesthebasefunctionality
forallcollections.
Collection<String> collection=newArrayList<>();
collection.add("A");
collection.add("B"):
collection.add("C");
for(Stringelerent
:collection) {
System.out printin(element);
ListInterface
TheListinterfaceextendstheCollectioninterfaceandrepresentsan
BasicOperations
l.boolean add(e) 6.voidadd(intindex,element)

4. I|method2
list.add("A";
list.add("B";
list.add("C");
for(inti=0;i<list.size(); i++)(
System.out. printin list.get(i);
System.0ut.printin(" Aftermodihcation:+arrayList);
I/Removingelements
arrayList.remove("C");
System.out. printin("Afterremoval:"+arrayList);
/Checking size
System.out.printin("Size ofArrayList:"+arrayList.size():
1/Checking ifArrayListcontainsanelement
System.out. printin("DoesArraylistcontain'A'?"+
arraylist.contains("A");
IteratorvsListiterator
Faature
Iterator Listiterator
/ClearingtheArrayList
arraylist.clear();:
System.out.printin ("Afterclearing:"+arrayList);
Applicable to Collection List
Traversal Direction Forwardonty Bothforwardandbackoard
Obtainingterator
hastiext(
ext()
hesPrevseus()
collectin.iterator()'
Nc
"it.itIterater()
LinkedlList
LinkedList isadoublylinkedlistimplementationoftheListinterface.
ItispartoftheJavaCollectionsFrameworkandisfoundinthejava.util
package.
Previo()
tIndes()
UnlikeArrayList,whichusesadynamicarray,LinkedListusesadoubly
ole

5. rviousndes()'
Ne
()
No
set(E) No
ArrayList
ArrayListisaresizablearrayimplementation oftheListinterface.
ItispartoftheJavaCollectionsFrameworkandisfoundinthejava.util
package.
Arraylistallowsfordynamicarraysthatcangrowasneeded,
whichmeansitcanchangeitssizeduringruntime.
KeyPoints:
UnlikearraysinJava,ArrayListcangrowandshrinkinsize
dynamically.
Allowsduplicateelements.
Provides fastrandomaccesstoelements.
Initialcapacity is10,butitgrowsautomaticallyaselementsare
added.
KeyPoints:
DoublyLinked:EachelementinaLinkedList isstored inanodethat
containsareferencetothenextandpreviouselements.
DynamicSize:Cangrowandshrinkdynamically.
Allowsduplicateelements.
Efficientforaddingorremovingelementsanywhere inthelist.
SlowerthanArrayListforrandomaccess(get(),asitrequirestraversing
fromtheheadortail.
BasicOperations:(SameasArraylist)
importjava.util.:
publicclassLinkedListExample(
publicstaticvoidmain(Stringl] args){
1/CreateoLinkedList
LinkedList<String> linkedlist=newLinkedList<>):
HAddingelements
linkedList.add("Apple");
linkedList.add("Banana");
linkedList. add("Cherry" );
importjava.util.Vector;
publicclassVectorExample
{
publicstaticvoidmain(String|]args)
{

6. orderedcollection(alsoknownasasequence).
Theusercanaccesselementsbytheirintegerindex(position inthelist)
andsearchforelementsinthelist.
KeyPoints:
Methods:
2.get(intindex)
3.remove(int index)
4.intsize()
5.booleancontains(e)
set(intindex,element)
8.booleanremove(e)
9.voidclear()
voidadd(intindex,Eelement):Insertsthespecified
elementatthespecifiedposition inthislist.
Eget(intindex):Returnstheelementatthespecified
position inthislist.
Eset(intindex,Eelement):Replaces theelementatthe
specifiedposition inthislistwiththespecifiedelement.
Eremove(intindex):Removestheelementatthe
specifiedposition inthislist.
intindexOf(objecto):Returnstheindexofthefirst
OCcurrenceofthespecifiedelementinthislist.
Listiterator<E> listlterator(): Returnsalistiteratorover
theelementsinthislist.
Implementations:
1.ArrayList 2.LinkedList 3.Vector 4.Stack
Usage:
TheListinterfaceallowsfororderedcollectionsthatcan
containduplicateelements.
List<String> list=newArrayList<):
I/List<integer>numbers=Arrays.asList(5.
2.8.13):method 1
importjava.util."
publicclassArrayListExample
{
publicstaticvoidmain(String]args){
7/CreatingonAraylist
List<String>arrayList=newArrayList<>();
1/Addingelements
arrayList.add("A"):
arraylist.add("B"):
arrayList.add("C");
arrayList.add("D");
HAccessingelements
System.out. printin("Element atindex2:"+arrayList.get(2));
iterotingeiements
for(Stringelement:arrayList) {
System.out.printin(element);
/Modifyingelements
arrayList.set(1, "E");

7. linkedList.set(1,"Orange"); 1/Modifyelement
linkedList.add(2, "Grape");//Addanelement
linkedList.remove("Apple"); //Removeelement
WCheckif"Banana"ispresent
booleancontainsBanana =linkedList.contains(" Banana");
System.out.printin("DoesLinkedListcontain'Banana'?"+
containsBanana);
System.out, printin("Printforwardorderelement"):
Listiterator<String> iterator=linkedList.listiterator():
while(iterator.hasNext() (
System.out,printin(iterator.next());
Vector<String> vector=newVector<>);
vector.add("A");IAddingelements
vector.add("B");
vector.add("C");
IAccessingelements
System.out printin("Elementatindex1:"+vector.get(1);
1/Removingelement
vector.remove(2);
/Sizeofvector
System.out.printin("Sizeofvector:"+vector.size):
System.out, printin("Printreverseorderelement");
while(iterator.hasPrevious()
System.out.printin(iterator.previous():
Arraylist(Collection<? extendsE>c)
Createsalistcontainingtheelementsofthespecifiedcollection,inthe
ordertheyarereturnedbythecollection's iterator.
ItissameForLinked List
istcStringoviciogi ictArravs
aslistA
C
Stack
StackisasubelassofVectorthatimplementsalast-in, first-out (LIFO)
stackofobjects.
Methods:
push(Eitem):Pushesanitemontothetopofthestack.
pop():Removestheobjectatthetopofthestackandreturnsit.
peek():Looksattheobjectatthetopofthestackwithout
removing
it.
isEmpty():Checksifthestackisempty.

8. List<Stringexistinglist =Arrays.asList("A","B","C");
Arraylist<String> list=newArrayList<>(existingList);
System.out,printin(list)://Output:(A, B,C]
LinkedList(Collection<? extendsE>)
List<String>arraylist=newArrayListo();
arrayList.add("Apple");
arrayList.add("Banana");
arrayList.add("Cherry");
1/CreateoLinkedistusingtheArrayListelerments
LinkedList<String> linkedlist=newLinkedList<>(arrayList);:
import java.util.Stack;
publicclassStackExample
publicstaticvoidmain(String]args)
{
Stack<String> stack=newStacko);
1IPushingelements
stackpush("A");
stackpush-B");
stack.push("C");
IPeekingthetopelement
System.out. printin("Topelement:"+stack.peek());

9. LinkedListvsArrayList
LinkedListprovidesmethods likeaddFirst,addLast,getFirst,getLast,
removeFirst,removelast,offerFirst,offerlast,peekFirst,peeklast,
pollfirst,pollLast,descendingiterator forefficient insertion,removal,
andtraversaloperationsfrombothends.
ArrayList isoptimizedforrandomaccessandefficientelement
insertion/removal inthemiddle.
Choosingbetweenthemdependsontheusecase:
UseLinkedListforfrequentinsertions/removals atbothendsor
sequentialtraversal.
UseArrayListforscenariosrequiringrandomaccessorfaster
accessbyindex.
Vector
Vector isapartoftheJavaCollectionsFrameworkandimplementsa
growablearrayofobjects.
Itissynchronized,makingitthread-safe,butcanhaveperformance
overheadduetosynchronization.
Methods:
add(e):Addsanelementtotheendofthevector.
get(intindex):Returnstheelementatthespecifiedposition.
remove(intindex):Removestheelementatthespecifiedposition.
size():Returnsthenumberofelementsinthevector.
System.out, printin("Poppedelement:"+stack.pop):
/Checking ifstockisempty
System.out. printin("Is stackempty?"+stack.isEmpty0):
QueueInterface
Queueisacollectiondesigned forholdingelementspriortoprocessing.
ittypicallyorderselementsinaFIFO(first-in, first-out)manner.
Implementations includeLinkedListandPriorityQueue.
Methods:
add(e):Insertsthespecifiedelementintothequeue(throwsan
exception ifitfails).
offer(e):Insertsthespecifiedelementintothequeue(returns
falseifitfails).
remove():Retrievesandremovestheheadofthequeue(throws
NoSuchElementExceptionanexception ifthequeueisempty).
poll():Rtrievesandremovestheheadofthequeue(returnsnul
ifthequeueisempty).
peek():Retrieves,butdoesnotremove,theheadofthequeue
(returnsnull ifthequeueisempty).

10. importjava.util.LinkedList;
importjava.util.Queue;
public classQueueExample(
publicstaticvoidmain(String|]args){
Queue<String>queue=newLinkedList<>():
IAddingelements
queue.add("A");
queue.add("B");
queue.add("C");
1/Peekingtheheodelement
System.out. printin("Headelement:"+queue.peek()):
1/inkedHashSetxample
Set<String> linkedHashSet =newLinkedHashSet<>();
linkedHashSet.add("B");
linkedHashSet.add ("A");
linkedHashSet. add("C");
System.out. printin("LinkedHashSet:"+linkedHashSet): /
1TreeSetexomple
Set<String treeSet=newTreeSeto);
treeSet.add("B"):
treeSet.add("A");
treeSet.add('C"):
System.out,prhtin("TreeSet:"+treeSet);/ABC
BAC
1IPollingelements
System.out. printin("Polledelement:"+queue.poll()):
1/Checkingthesize
System.out.printin("Size ofqueue:"+queue.size();
HashSet:Fostestforbasicoperotions, noguaranteedorder.
LinkedHashSet: Maintoins insertionorder,slowerthonHashSet.
TreeSet: Maintainselements insortedorder,slowerthanHashSetondLinkedHoshSet.
MapInterface

11. SetInterface
Represents acollectionthatcannotcontainduplicateelements.
Itmodelsthemathematical setabstraction.
Doesnotguaranteetheorderofelements.
Allowsatmostonenullelement.
Implementations includeHashSet,LinkedHashSet,andTreeSet.
HashSet
ImplementstheSetinterfaceusingahashtable.Itdoesnotguarantee
theorderofelements.
Offersconstant-timeperformanceforbasicoperations(add,remove,
contains).
Doesnotmaintaintheinsertionorder.
Allows nullelements.
Represents acollectionofkeyvaluepairswhereeachkeyisunique.
Mapskeystovaluesanddoesnotallowduplicatekeys.
methodsforadding,accessing,removing,andcheckingforkey-value
pairs.
HashMapClass
ImplementstheMapinterfaceusingahashtable.
Doesnotguaranteetheorderofkey-value pairs.
Providesconstant-time performanceforbasicoperations (put,get,
remove)onaverage.
Allows nullvaluesandonenullkey.
importjava.util.HashMap,
importjava.util.Map;

12. LinkedHashSet
ExtendsHashSetandmaintains adoubly-linked listofentriesto
preservetheinsertionorder.
Iteratesoverelementsininsertionorder.
SlowerthanHashSetforbasicoperationsduetomaintaining order.
Allowsnullelements.
SortedSetInterface
publicclassHashMapExample
publicstaticvoidmain(Stringl] args)(
Map<String,Integer>hashMap=newHashMap<>();
hashMap.put("One", 1);
hashMap.gt("Two", 2);
hashMap.put("Three", 3);
System.out, printin("HashMap:"+hashMap);
ExtendsSetandmaintainselementsinsortedorderdefinedbytheir
naturalorderingoracomparator.
Providesmethodsforaccessingelementsbytheirposition inthesorted
set.
LinkedHashMap Class
EvtendeHachManandmaintainc incortionorderofkove

13. Set.
ImplementationsincludeTreeSet.
TreeSet
ImplementsSortedSetusingatreestructure(red-blacktree).
Maintainselementsinsortedorder(ascendingbydefaultorbasedona
customcomparator).
SlowerperformanceforbasicoperationscomparedtoHashSetand
LinkedHashSet.
Doesnotallownullelements.
ExampleOfAllSetsinterface
import java.util.";
publicclassSetExamples {
publicstaticvoidmain(Stringl] args){
1/HashSetexomple
Set<String>hashSet=newHashSet<>();
hashSet.add("B");
hashSet.add("A");
hashSet.add("C");
System.out.printin ("HashSet:"+hashSet);/CBA
ExtendsHashMapandmaintainsinsertionorderofkeys.
Iteratesoverelementsintheordertheywereinserted.
SlowerperformanceforbasicoperationscomparedtoHashMapdueto
maintaining order.
Allowsnullvaluesandonenullkey.
import java.util.LinkedHashMap;
importjava.util.Map;
publicclassLinkedHashMapExample
{
publicstaticvoidmain(Stringl] args){
Map<String, Integer>linkedHashMap=newLinkedHashMap<>():
linkedHashMap.put(One",1);
linkedHashMap.put("Two",2);:
linkedHashMap.put("Three", 3):
System.out.printin("LinkedHashMap:" +linkedHashMap);

14. HoshMop:Fastestforbasicoperotions, noorderguarantee.
LinkedHashMap: Maintoins insertionorder,inheritsfromHoshMap.
TreeMap: Maintains keysinsortedorder,slowerforbasicoperotions duetosorting.*
HashtableClass
TheHashtableclassinJavaprovidesabasicimplementationofahash
table,whichmapskeystovalues.
ItinheritsfromtheDictionaryclassandimplementstheMapinterface,
makingitsimilartoHashMapbutwithsomedifferences:
Hashtable issynchronized,
Neitherkeysnorvaluescanbenul
importjava.util.Hashtable;
int[]nums=(5,2,8,1,3};
Arrays.sort(nums); //Sortsnumsarrayinascendingorder
SortingCollections
1.Collections.sort():Sorts collectionssuchaslistsusingnatural
ordering (ifelementsimplementComparable)oraspecified
Comparator.
List<String>names=newArrayList<>);
names.add("Alice"
);:
names.add("Bob");
Collectils.sort(names); //Sortsolphobetically (noturalorder)
2.SortingwithComparator:ascending orderuse:
Comparator.naturalOrder() anddescendingorderuse:
Comparator.reverseOrder()
publicclassHashtableExample(
public staticvoidmain(Stringl] args){
/UsingHoshtable
HachtabloStrinalntoGArhachtablo noMHachtahlocs
List<String>names=newArrayList<>();
names.add("Alice"):
names.add("Bob");
Collections.sort(names, Comparator.reverse Order()://Sortsin

15. System.out.printin("Hashtable:" +hashtable);
IteratorsusedinMapandSet
importjava.util.";
ComparableInterface
Comparable isaninterfaceinthejava.langpackage.
ItdeclaresonemethodcompareTo()whichcomparesthecurrentobject
(this)withanotherobjectofthesametype.
ClassesthatimplementComparablecanbesortedautomatically using
methodslikeArrays.sort()orCollections.sort().
publicclassSetMaplterationExample
{
publicstaticvoidmain(Stringl]args)(
7CreateaHashSet
Set<String> set=newHashSetc>);
HAddelementstotheSet
set.add("Apple");
set.add("Banana");
set.add("Orange");
1/terating overtheSetusingfor-eochloop
System.out. printin("Elements intheSet:");
for(Stringelement:set)(
System.out.printin(element);
publicinterfaceComparable<T>{
publicintcompareTo(T o);
ExampleofComparableInterFace
publicclassStudentimplementsComparable<Student> {
privateStringname;
privateintage;
1HConstructor
publicStudent(Stringname,intage) {
this.name=rtome;
this.ageage;
1/CreateoHashMop
Map<String, Integer>map =newHashMap<o);

16. publicintcompareTo(Studentother)(
/Comporestudentsbasedonage
returnInteger.compare(this.age, other.age):
7Exompleusogeinmoinmethod
publicstaticvoid main(String
[]args){
List<Student> students=newArrayList<>():
students.add(newStudent("Alice", 20));
students.add(new Student("Bob",18);
students.add(newStudent("Charlie", 22));
/SortingusingCollections.sort)(usesComparable)
Collections.sort(students);
/Printingsortedstudents
System.out.printin ("SortedStudentsbyAge:");
for(Studentstudent:students)(
System.out. printin(student);
PropertiesClass
Properties storeskey-valuepairswherebothkeysandvaluesarestrings.
Itsupportsloadingfromandsavingtofilesusingload()andstore()
methods.
Defaultvaluescanbesetandqueried ifaproperty isnotfoundinthe
currentinstance.
Javasystemproperties (System-getProperties()) areaccessiblethrough
aProperties object.
Exampleusageinvolvessetting,savingtofile,loading,andaccessing
properties.
lItprovidespersistence forapplicationsettingslikedatabase
connectionsandUlconfigurations.
methods:
setProperty(String key,Stringvalue):Setsakey-valuepairinthe
Propertiesobject.
getProperty(String key):Retrievesthevalueassociated witha
specified key.
store(OutputStreamout,Stringcomments):Savesproperties to
anoutputstream,withoptionalcomments.

17. Comparator Interface
TheComparatorinterface inJavaislocated inthejava.util package.
Itdefinestwomethods:compare(To1,To2)andequals(Object obi).
YoutypicallycreateaninstanceofComparatoreitherasananonymous
class.
Comparator iscommonlyusedwithsortingmethodslike
Collections.sort() forlistsorArrays.sort()forarraystodefinetheorder
inwhichelementsshouldbesorted.
ExampleofComparatorInterface
importjava.util.;
public classStudent
{
private Stringname;
privateintage,
publicStudent(Stringname,intage)(
this.name=name;
this.age=age,
intgetAge()(returnthis.age;)
load(InputStream in):Loadspropertiesfromaninputstream.
stringPropertyNames(): Returnskeyswhereboththekeyand
valuearestrings.
importjava.io.";
importjava.util.;
publicclassStudent(
publicstaticvoidmain(String[] args)(
Propertiesprop=newProperties();
/Settingproperties
prop.setProperty( "database.url", "jdbc:mysql:/localhost:3306/mydb");
prop.setProperty( "database.user","root");
p.setProperty "database.password","password");:prop.
/Sovingproperties toafile
try(OutputStreamoutput=new
FileOutputStream("config. properties") (
prop.store(output, "DatabaseConfiguration");
System.out.printin ("Propertiessavedsuccessfully.");
}catch(1OException e)(
e.printStackTrace():
nuhlic staticunid mainLStrinalLarc)

18. public staticvoidmain(Stringl] args)
{
List<Student>studentsnewArrayListo:
students.add(new Student("Alice,20):
students.add(newStudent("Bob", 18)):
students.add(new Student(" Charlie",22):
HUsingComporotor tosortbyogeindescendingorder
Comparator<Student> ageComparator anewComparator<Student>()
Override
publicintcompare(Student s1,Students2)(
returninteger.compare(s2 getAge),s1getAge()l: //Descending order
/Loodingpropertiesfromofile
try(InputStream input=newFileinputStream("config properties") {
prop.load(input);
System.out,printin("Propertiesloadedsuccessfully.");
/Displayproperties
prop.forEach(key, value)->(
System.out. printin(key+";"+value);
7SorongsTudentshstusingogeCormporotor
Collections.sort(students,ageComparator);
1/Accessingindividuolproperty
StringdblUrl=prop.getProperty(" database.url");
System.out. printin("DatabaseURL:"+dbUri);