java for beginners
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LEARNINGSTARTSWITHVIEWINGTHEWORLDDIFFERENTLY.
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JAVAFORBEGINNERS1.IntroductiontoJava
2.Featuresofjava
3.DataTypes,VariablesandArrays
4.Operators
5.Controlstatements
6.Classesandmethods
7.Inheritance
8.PackagesandInterface
9.ExceptionHandling
10.EventHandling
11.TheAppletClass
12.MoreeBooksandApps
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DisclaimerThiseBookcontentsisforinformationalandstudypurposesonly.TheKnowledgeflowmakesnoclaims,promises,orguaranteesabouttheaccuracy,completeness,oradequacyofthecontentsofthiseBookandnolegalliabilityorotherresponsibilityisacceptedbyKnowledgeflowforanyerrors,omissions,orstatementsonthiseBook.
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IntroductiontoJavaJavawasdesignedandconceivedbyJamesGosling,PatrickNaughton,ChrisWarth,EdFrankandMikeSherdan,whichwasdoneatSunMicrosystemsinyear1991.
Ittookalmost18monthsforjavatocomeintoexistenceasaworkingversion.
InitiallyjavawasknownasOak,whichwasthenrenamedasJavainyear1995.SincejavahadmuchhadmuchofitscharacterdesignedfromCandC++.
Thischaracterinheritedbythetwowellknownandsimpleprogrammingmakesjavamoreappealingtocomputeranditgiantswhichwouldleadtoalargescalesuccess.
ButjavaismisunderstoodasthesophisticatedinternetversionrepresentationofC++.
IthassignificantdifferencepracticallyandphilosophicallywhencomparedtoC++.
IfyouhavegoodknowledgeinC++thenyouwillfindjavaasyourcupofteaandyouwillateaseusingandunderstandingjava.
LogoofJava
Therefore,therearetwomainreasonsfortheevolutionofthecomputerlanguages.
JavahadenhancedandrefinedtheobjectorientedscenarioofC++.Thisgavemorefeaturestotheuserswhichareasfollows.
Multithreading.
Librarywhichwouldprovideeasyinternetaccess.
Oneofthejavasmagicwasthebytecode.Bytecodeissetofinstructionwhichis
-
highlyoptimizedanddesignedtobeexecutedbyJVM(JavaVirtualMachine).Itisaninterpreterforbytecode.Thisleadtothedesignoftrulyportableprograms.
Javaredesignedtheinternetwithnewfeatureandnetworkedprogramwhichareasfollows.
Applets-Itisakindofjavaprogramthatistobetransmittedoverandexecutedautomaticallybyjavacompatiblewebbrowsers.
Security-ItprovidedthesecurityofdownloadingvariousappletsandprogramsfrominternetwithoutcontaininganyvirusorTrojanhorses.
Portability-SincethereislargeanddifferentkindofoperatingsystemsthereforeitprovidesthefreedomofrunninginanyoperatingsystemsoitsprogramcanbeusedindifferentOSwithoutanyissuesofcompatibility.
Theevolutionsinjavaareasfollows.
Java1.0
Java1.1
Java1.2
J2SE
J2SE1.2
J2SE1.3
J2SE1.4
J2SE5
J2SE5madevariouschangestoJava
Thenewfeaturethatwasaddedisasfollow.
Generics
Annotations
Autoboxingandauto-unboxing
Enumerations
Enhanced,for-eachstyleforloop
Variable-lengtharguments
Staticimport
FormattedI/O
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Concurrencyutilities
InJ2SE5,andthedeveloperskitwascalledJDK5.1.5usedasinternalversionnumberandthisisreferredasdeveloperversionnumber.
Javabecamethecenterofinnovationincomputertechnologicalworld.TheexistenceofJVMandbytecodechangedthescenarioofsecurityandportabilityintheprogrammingworld.ThewaythenewideasareputintothelanguagehasbeenredefinedbytheJCPi.e.javacommunityprocess.
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FeaturesofJavaObject-orientedprogramming
Thisisthecorefeatureofjava.Thisistomanagetheincreaseinthecomplexity.Itprovidesaverysophisticatedandwelldefinedinterfaceforthedata.Itisalsoknownasdatacontrollingaccesscode.Anotherimportantfeatureofjavabeingobjectorientedisabstraction.Complexitycanbemanagedusingabstraction.
ThethreeOOPprinciples
Encapsulation-Itsagendaistomanipulatethedataandkeepthedataisolatedandsafefromtheexternalinterferenceandmisuse.Theencapsulationisdonebytheuseoftheprotectivewrapper.Thispreventstheexternalsourcesfromaccessingthedataorthecode.
EncapsulationinJava
Inheritance-Inthistheobjectwouldacquirethepropertyofotherobjectpresent.Itjustfollowstheconceptofthehierarchicalclassification.Thisconsistsofclasses,subclasses.Inheritancealsoislinkedorinteractswithencapsulationaswell.
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Inheritance
Polymorphism-Itismeansmanywaystocarryoutthemethodbutfromoneinput.
Polymorphism
Bytecode
ThisishighlyoptimizedbysetofinstructionsdesignedwhichisdesignedtobeexecutedbyJavavirtualmachinethatisJVM.
JVM
Itwasdesignedasaninterpreterforthebytecode.Anotherfeatureofjavaprogramisthatitissimple.Thisenablestheprofessionalstolearn.Workinaveryeffectivemannerbutitisalsoveryeasytounderstand.
Robust
TheabilitythatincludescreatingarobustprogramthatcanbeamultiplatformprogramaregivenaveryhighpriorityindesignofJava.
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Multithreading
Therealworldrequirementsaremetbyjavawhichhelpstoachievetherequirementofcreatinginteractiveandnetworkedprograms.
Highperformance
Theadvantageofbeingamultiplatformfunctioningprogramhelpstofindthecrossplatformsolution.Itprovidesbenefitsofbeinganplatformindependentcodewiththehelpofjavaruntimesystem.
Distributed
ThisisbecauseitisbeendesignedfortheinternetwhichhasadistributedenvironmentbecauseofthehandlingofTCP/IPprotocols.Thisallowstheprogramtofindoutmethodsacrossanetwork.URLisusedinthistoaccessafileoninternet.ThispropertysupportsRMI(RemoteMethodInvocation).
Dynamic
Thisistheactionthatistakenduringtherun-timesuchastoresolve,verifyandaddobjects.Itprovidesusthefunctionwhichwillallowustolinkcodedynamicallythatwillbesafe.
Simpleprogram
/*CallthisfileExample.java*/
ClassExample{
Publicstaticvoidmain(stringargs[]){
System.out.println(thisisasimplejavaprogram.);
}
}
Commandlineargumenttopasstheclassnameis
C:\>javaExample
Simpleoutputoftheaboveprogram
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thisisasimplejavaprogram.
Callingofthefileinjavacmd
Callingofthefile:Example.java.
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DataTypesIntegers
Itincludeswholevaluedsignednumberswhichareasfollow.
Byte-Whosewidthis8anditrangesfrom-128to127.Itisthesmallestintegertype.Itisusefulwhenuserisdealingwithstreamorflowingdatafromanetworkorafile.
Declarationoftwobytevariablescalledxandyisasfollow
Bytex,y;
Short-Thewidthofthistypeofintegeris16anditrangesfrom-32,768to32,767.Itistheleastcommonlyuseddatatypeinjava.
Declaration
Shorta;
Shortb;
Int-Thewidthofthistypeofintegeris32anditrangesfrom-2,147,483,648to2,147,483,647.Itismoreefficientascomparedtobyteandshort.Itiscommonlyusedtocontrolloopsandindexedarrays.
Declaration
Inta;
Long-Thewidthofthistypeofintegeris64anditrangesfrom-9,223,372,036,854,775,808to9,223,372,036,854,775,807.Thisisusedforthosevalueswhicharelargeenoughthattheintegercannothandlethem.
Declaration
Intlightspeed;
Longdays;
Longsecond;
Seconds=days*24*60*60;
Floatingpointtype
Thisisforrealnumbersusedforcalculationsuchassquareroots,sineandcosine.Theseareoftwotypes.
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Float-Widthinbitsis32andrangeisfrom1.4e-045to3.4e+038.Floatisusedasavariabletypeforthefractionalcomponent,butspecifiessingleprecision.Itcanbeusedinrepresentingdollarsandcents.
Declaration
Floathightemp;
Double-Widthinbitsis64andrangeisfrom4.9e-324to1.8e+308.itisusedandisoptimizedinsuchawaythatIcanbeusedforhighspeedmathematiccalculation.Ithasdoubleprecisionwhichisfasterthanthesingleprecision.Functionsuchassin()andsqrt()etc,returndoublevalues.
Declaration
Doublepi,r,a;
r=10.4;
pi=3.14;
a=pi*r*r;
Characters
Thedatatypeusedstoreordeclarecharacterinjavaischar.Itis16-bittypeinjava.Rangeofacharis0to65,536.Therearenocharswhicharenegativeinnature.
Programdemonstrationforchar
ClasscharExample
{
Publicstaticvoidmain(Stringargs[]){
Chara,b;
a=88;
b=y;
system.out.print(aandb:);
system.out.println(a++b);
}
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}Booleans
Itisaprimitivetypeforlogicalvalues.Thistendshaveonlyoneoftwopossiblevalues,trueorfalse.Itisgovernedbyiforforcontrolstatements.
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VariablesItisbasicunitofstorageandvariableshavescope,visibilityandlifetime.
Declarationofvariables
Intx,y,z;
Or
Intx=1,y=2,z=5;
Typeconversionandcasting
Ifthereisanycompatibilityexistingbetweentwotypesthenjavawouldautomaticallyperformstheconversion.
Javaautomaticconversion
Itwillbeperformedwhentwoconditionsaremet.Whenthetwotypesarecompatible;Destinationtypeislargerthanthesourcetype.Afterthetwoconditionsarebeensatisfiedawideningconversiontakesplace.
Castingcompatibletypes
Itisasimpleandexplicittypeofconversion.Whenafloatingtypeofconversionisattachedtoanintegertypethistypeofconversioniscalledtruncation.Itisakindofconversionsometimecallednarrowingconversion.
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ArraysItisagroupofsimilarvariablesthatwouldbereferredbyacommonname.Theelementavailableinthearrayisaccessedthroughindex.Thiscanbecreatedandmayhaveoneormoredimension.
Typesofarrays
Therearetwomaintypesofarraysare.
1. One-dimensionalarrays2. Multi-dimensionalarrays
One-dimensionalArrays
Itsalistofsimilartypesofdata.Beforeyoucreatearrayyouneedtocreateavariableofanytype.
Syntax
Typevariable-name[];
Intyear_month[];
Multi-dimensionalArrays
Itisarraysofarraysneedtospecifyeachdimensionalarrayvariables,additionalindexusingothersquarebracketsrepresentedas.
InttwoD[][]=newint[6][7];
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OperatorsTherearefourmaintypesofoperator.
ArithmeticoperatorsTheBitwiseoperatorsRelationaloperatorsBooleanlogicaloperators
Arithmeticoperators
Addition-Thisoperatorisusedtoaddthevalues.Itisrepresentedby+.ForexampleA=a+4.Subtraction-Thisoperatorisusedtosubtractthevalues.Itisrepresentedby-.ForexampleA=a-4.Multiplication-Thisoperatorisusedtomultiplythevalues.Itisrepresentedby*.ForexampleA=a*4.Division-Thisoperatorisusedtodividethevalues.Itisrepresentedby/.ForexampleA=a/4.Modulus-Thisoperatorisusedtofindtheremainderofthevalueswhendivided.Itisrepresentedby%.ForexampleA=2%4.WhereA=0.Increment-Thisoperatorisusedtoincreasesitsoperandbyone.Itisrepresentedby++.Forexamplea=a++whichisequaltoa=a+1.Decrement:Thisoperatorisusedtodecreasesitsoperandsbyone.Itisrepresentedby.Forexamplea=awhichisequaltoa=a-1.
Bitwiseoperators
UnaryNOT-Thisinvertsallofthebitsofoperandcontainedanditisrepresentedby~.
Forexample
~00101010=11010101
And-Itproduces1bitifbothoperandsarealso1anditisrepresentedby&.
Forexample
00101010
&00001111
000101010
OR-Ifeitheroftheoperandisoneitproduces1andItisrepresentedby|.
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Forexample
00101010
|00001111
00101111
XOR-Ifeitherofthebitoperandis1,thenresultisalsooneotherwiseits0anditisrepresentedby^.
Forexample
00101010
^00001111
00100101
Leftshift-Itshiftsormovesallofthebitsintheparticulargivenvaluetotheleftsidenumberoftimesthatisbeendeclaredanditisrepresentedby .
Rightshift-Itshiftsormovesallofthebitsintheparticulargivenvaluetotherightsidenumberoftimesthatisbeendeclaredanditisrepresentedby .
Relationaloperators
Equalto-Thisrelationoperatorshowsthatthevaluesareequaltoeachotheranditisrepresentedby==.
Notequalto-Thisrelationoperatorshowsthatthevaluesarenotequaltoeachotheranditisrepresentedby!=.
Greaterthan-Thisrelationoperatorshowsthatonevalueisgreaterwhencomparedtootheranditisrepresentedby>.
Lessthan-Thisrelationoperatorshowsthatonevalueislesswhencomparedtootheranditisrepresentedby=.
Lessthanorequalto-Thisrelationoperatorshowsthatonevalueissmallerorequalbutnotgreaterwhencomparedtootheranditisrepresentedby
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A&B=Ifaisfalseandbistrueitresultsasfalse,butisbotharetrueitresultsastrue.Similarlywhenbotharefalseitresultsasfalse.
LogicalOR-Itissigned|.
Forexample
A|B=Ifaisfalseandbistrueitresultsastrue,butisbotharetrueitresultsastrue.Similarlywhenbotharefalseitresultsasfalse.
LogicalXOR-Itisshownusing^.
Forexample
A^B=Ifaisfalseandbistrueitresultsastrue,butisbotharetrueitresultsasfalse.Similarlywhenbotharefalseitresultsasfalse.
LogicalUnaryNot-Itisdepictedas!.
Forexample
!A=Ifaisfalseitresultsastrue,butifaistrueitresultsasfalse.
Assignmentoperators
Theassignmentisthesingleequalsignthatisrepresentedby=.
Thegeneralrepresentation
var=expression;
Inthisthevariable,whichisrepresentedas var shouldbecompatiblewiththetypeofexpression.
Inta,b,c;
a=b=c=100;
The?Operator
Thisisusedforreplacementofifthenelsestatementsanditisrepresentedas?.
Forexample
expressiona?expressionb:expressionc
Thisaboveexamplestatesthatiftheexpressionaistruethenexpressionbisevaluatedotherwiseexpressioncisevaluated.
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ControlStatementsTherethreetypesofstatementsinjava.
1. Selectionstatements2. Iterationstatements3. Jumpstatements
Selectionstatements
Itistomanagetheflowofprogramsthatistobeexecutedbasedonthedynamicconditionswhichcanbeonlyrealizedduringtheruntime.Itprovidesflexibility.
Ifstatement-Itprovidesdifferentpathsforexecutionofprogram.
Syntax
If(conditionprovided)statementa;
Else
Statementb;
Thismeansiftheconditionistrue,thenstatementaisexecutedbutiffalsethenstatementbisexecuted.
Forexample
inta,b;
If(x0)
{
System.out.println(tick+n);
n;
}
}
}
Output
Itwilltick5times
Tick5
Tick4
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Tick3
Tick2
Tick1
Do-whilestatement
Thisloopexecutesitsbodyatleastoncebecauseitcontainsitsconditionexpressionatthebottomoftheloop.
Syntax
do
{
System.out.println(tick+n);
n;
}
Whilen>0);
}
}
Forstatement
Itisaverypowerfulaswellasveryversatileconstruct.Theconditionwhatisprovidedinforstatementuntilandunlesstheconditionisnotbeensatisfieditwontexecute.Iftheconditionisevaluatedandthevalueisfalsethenitisterminated.
Syntax
For(initialize;condition;iterate)
{
Body
}
Forexample
Classfortick
{
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Publicstaticvoidmain(stringargs[])
{
Intn;
For(n=11;n>0;n);
}
}
Jumpstatements
Javasupportsthreejumpstatementswhichareasfollows.
1. Break2. Continue3. Return
Break
Itisusedtoterminateastatementwhichisinsequenceinaswitchstatementanditcanbeusedforexitingaloop.SometimeItcanbeusedinsteadofgoto.
Continue
Itprovidesanearlyiterationforaloop.
Forexample
Classcontinue
{
Publicstaticvoidmain(stringargs[])
{
For(inti=0;i
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}}
Return
ItisusedtoreturnfromamethodandItisatransferbackcallingofthemethod.
Forexample
Classreturn{
Publicstaticvoidmain(stringargs[])
{
Booleant=true;
System.out.println(return);
If(t)return;
System.out.println(thiswontwork);
}
}
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ClassesandMethodsClassesmightcontainonlycodeordatabutmayalsocontainboth.Aclassisdeclaredbykeywordclassanditcanbecomplexinnature.
Syntax
Classclassname
{
Typeinstance-variablea;
Typeinstance-variableb;
.
.
.
Typeinstance-variablen;
}
Typemethoda(parameter-list)
{
//bodyofmethod
}
Typemethodnamea(parameter-list)
//bodyofmethod
.
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.}
}
Classesarealsocalledtheboxwhichdefinesvariable-width,heightanddepth.
Example
Classbox
{
Doublewidth;
Doubleheight;
Doubledepth;
}
Classthatimplementsstackofdataandinteger.
Example
Classstack
{
Intstk[]=newint[10];
Stack()
Tos=-1
}
Voidpush(intitem){
If(tos==9)
System.out.println(itsfull);
Else
Stk[++tos]=item;
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}Intpop()
{if(tos
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OverloadingmethodWhentwoormoremethodsaredefinedinthesameplaceandthenamedefinedissamebuttheparametersaredifferent.Thismethodisanoverloadingmethod.Thisprovidespolymorphisminjava.
Example
Classoverload1
{
Voidtest(){
System.out.println(noparameter);
}
Voidtest(inta)
{
System.out.println(a:+a);
}
Voidtest(inta,intb)
{
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System.out.println(aandb:+a++b);
}
Doubletest(doublea)
{
System.out.println(doublea:+a);
Returna*a;
}
}
Classoverload
{
Publicstaticvoidmain(stringargs[])
{
Overload1ob=newoverload();
Doubleresult;
ob.test();
ob.test(10);
ob.test(10,20);
Result=ob.test(123.25);
System.out.println(result:+result);
}
}
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Output
A=10
AandB=1020
Doublea=123.25
Result=15190.5625
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InheritanceInheritanceisasuperclassfromwhichalltheclassesareinheritedandwhichdoesinheritingfromasuperclassiscalledthesubclass.
Basicprogramofinheritance
Classx
{
inti,j;
voidshowIj()
{
System.out.println(iandj:+i++j);
}
}
Classyextendsx
Inta;{
System.out.println(a:+a);
}
Voidsum()
{
System.out.println(i+j+a:+(i+j+a));
}
}
Classsimpinheritance
{
Publicstaticvoidmain(stringargs[])
{
qSuperob=newq();
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psuperob=newp();
Subob.i=8;
Subob.j=7;
Subob.a=9;
System.out.println(contents);
Subob.showij();
Subob.showa();
System.out.println(sumofi,janda);
}
}
Output
Contents:Iandj:87
a:9
Sumofi,janda:i+j+a:24
Mainuseofinheritanceinjavaisforoverridingandcodereusability.
Overriding
Whensubclassesareidenticalofasuperclassthisscenarioiscalledmethodoverriding.Itprovidesthecharacteristiccalledpolymorphisminjava.
Inheritanceshowingoverriding
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Examplecode
Classx{
inta,b
X(intp,intq)
{
p=a;
q=b;
}
Voidshow()
{
System.out.println(aandb:+i++j);
}
}
Classyextendsx{
Intr;
Y(inta,intb,intc)
{
Super(a,b);
r=c;
}
Voidshow(){
System.out.println(r:+r);
}
}
Classoverride{
Publicstaticvoidmain(stringargs[])
{
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ysubob=newy(1,2,3);
Subob.Show();
}
}
Output
r=3
Typesofinheritance
Therearethreetypesofinheritance.
SingleinheritanceMultipleinheritanceHierarchicalinheritance
Typesofinheritance
Injavamultipleandhybridwillonlysupportedwithuseofinterface.
Multipleandhybridinheritance
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PackagesPackagescontainnameswereclassesarestored.
Syntax
Packagepkg;
Torepresentmultipackaging
Packagepkgx[.pkgy[.pkgz]];
Forexample
Packagejava.awt.imagea;
Findingofpackages
Therearethreewaystofindthepackages.Thejavaruntimesystemusestheworkingdirectory;ifthepackageiscontainedinthesubdirectorythenitwillbediscoveredoryoucansetthelocationbysettingthelocationofclassasshown.
Packagempack
Itcanuseclasspathwithjavaaswellasjavactospecifythelocationofclassasshown.C:\ myprograms\java\mpack
Accessprotection
Fortheprotectionofpackagestherearethreespecifiersinexistenceinjava.
1. Private-cannotbeseenoraccessedfromoutsidetheclass.2. Public-ithasfeaturetobeaccessedfromanywhere.3. Protected-thiscanbeaccessedonlybyclasseswhicharesub-classes.
Packagesyntax
Importingapackage
Thestatementthatimportsthepackagecomeimmediatelyafterthepackagingstatementanditsmainfunctionistoimportthepackagebysavingmoretimetoitslocation.
Syntax
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Importpkga[.pkgb].(classnamed*);
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InterfaceItissimilartoclasswhichcontainsconstants,methodsandsignatures.
Javasimplecalculatorinterface
Interfaceforjava
Declaration
Accessinterfacem
{
Returnmethod1(parameterlist);
Returnmethod2(parameterlist);
Typefinalvariablename1=value;
Typefinalvariablename2=value;
//
Returntypemethodnamen(parameterlist);
Typefinalvarnamen=value;
}
Simpleinterfacecontainsonlyonefunctionormethodknownascallbackfunction.
Forexample
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Interfacecallback
{
Voidcallback(intparm);
}
Implementinginterface
Tocreatinganyinterfaceimplementationofclassisincludedindefinitionofaclass.
Forexample
Classclientcallback
{
Publicvoidcallback(intx)
{
System.out.println(callback+x);
}
}
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ExceptionalHandlingItisadrawbackthataffectstheperformanceofjavaprogrambecauseitcanoccuratanypoint.Itoccurrenceisatexecutionstate.
Reasons
InvaliddataFileabsentLossofnetworkconnectionandtimeoutwhentheJVMisatrun.
Thecommonexceptionsare.
Checked-Theseexceptionscannotbeforecastedbytheprogrammeranditcannotbeevenignoredduring.
Runtime-Thisisadynamicexception,butitcanbeignoredunlikethecheckedone.
Errors-Thesearealsoignoredbecausenothingcanbedonetoovercomeitandthisisnotunderprogrammerscontrol.
Exceptionhierarchy
Ithastwosubdivisions:Inputoutputexceptionclassesandruntimeexceptionclass.
Throw
TheseareexceptionswhicharethrownbyJVMduringruntime.
Syntax
throwThrowableinstance;
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Throw
Whenthisstatementisusedthereisanimmediatestopintheexecutionofprogram.
Forexample
Classthrowdem
{
Staticvoiddemopro()
{
Try{
ThrownewNullPointerException(dem);
}catch(NullPointerExceptione)
{
System.out.println(caughtinsidedemopro.);
Throwe;
}
}
Publicstaticvoidmain(stringargs[]{
-
Try{
Demopro();
}
Catch(NullPointerExceptione){
System.out.println(recatch:+e);
}
}
}
Finally
Itisacodethatisusedinexecutingbeforeorafterthetryandcatchblockisexecutedorcompleted.
Syntax
Classfinallydem
{
Staticvoidprox()
{
Try
{
System.out.println(inprocx);
ThrownewruntimeException(demo);
}
Finally
{
System.out.println(proxfinally);
}
}
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EventhandlingEvent
Itshowsthechangeinstateofasource.
Eventsources
Itisanobjectgeneratinganevent.
Syntax
PublicvoidaddTypeListener(TypeListnerl)
Forexample
Addkeylistner()-toregisterakeyboardevent.Addmousemotionlistner()-toregisteramousemotionlistener.
ActionEventClass
Thishappenswhenbuttonispressed.Doubleclickingoftheitemoranyiteminthemenuisselected.
Eventoccurrenceinjava
Keyeventclass
Thisgeneratedfromthekeyinputofthekeyboardandtherearethreetypesofkeyevents.
1. KEY_PRESSED
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2. KEY_RELEASED3. KEY_TYPED.
Mouseeventclass
Thereareeighttypesofmouseeventclasses.
1. MOUSE_DRAGGED2. MOUSE_CLICKED3. MOUSE_ENTERED4. MOUSE_EXITED5. MOUSE_MOVED6. MOUSE_PRESSED7. MOUSE_RELEASED8. MOUSE_WHEELED
Actionlistenerinterface
Itisusedtodefinetheactionstheseareallperformedwhichareinvokedatthecallofanevent.Itisusedtoknowthereactionofthemethod.
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TheAppletclassItcontainsseveralmethodswhichareusefulforjavaexecutionanddetailedcontrol.TheAppletinitializationandterminationareasfollow.
Forstarting
init()-Usedtoinitializemethoditisthefirstmethod.
start()-Afterinitializationmethodthismethodcomesanditsfunctionistorestartordisplayonscreen.
paint()-Inthistheoutputoftheappletisredrawneachtimeitiscalled.
Forstopping
stop()-Itistoleavethebrowserwhichisopenedandcontainsapplet.
destroy()-Itisfortheappletoncewhichhastoremovedfromthememory.
Appletgeneration
HTMLapplettag
-
WIDTH=pixelsHEIGHT=pixels
[ALIGN=alignment]
[VSPACE=pixels][HSPACE=pixels]
>
[PARANAME=attributenameVALUE=attributevalue>]
[HTMLdisplayedinabsenceofjava]
HTMLApplettag
TheAudioclipinterface
play()-Tobegintheaudio.
stop()-Tostoptheaudio.
loop()-Toplaytheloopwithoutbreak.
TheAppletsubinterface
ItprovidesalinkthroughwhichanAppletandthebrowsercancommunicate.
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