ABAP OO Concept Topicwis Example _ Maagnusabap

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maagnusabap

ABAPOOConceptTopicwiseExample

INDEX

1Class.5

1.1Accessibilityofdifferentsectionsofaclass.5

1.2Subclasscannotaccesstheprivatecomponentofsuperclass.8



1.3Externaluserscannotaccessprotected/privatecomponentsofaclass.9

1.4LocalClasscanunderstanddataandtypesintheglobalareaoftheprogram.10

1.5Classcanbeinstantiatedwithinimplementationofanotherclass.12

1.6DeferredDefinitionofaClass.13

1.7Placetoputnondeclarativestatements.14

1.8UseofFieldSymbolsinClass.15

1.9UseofStaticAttributes.16

1.10CreationofGlobalclassandusingitinalocalprogram..17

2Methods.22

2.1Methodwithoneimportparameter/onlyonenonoptionalparameter.22

2.2Importparameterspassedbyref.cantbechangedinsidethemethod.23

2.3UseofPREFERREDPARAMETERinamethod.24

2.4UseofEXPORTandCHANGINGparametersofamethod.25

2.5MethodusingInternalTableasoneoftheparameters.26

2.6UseofRETURNINGparametersinmethod.27

2.7DemoonStaticMethod.28

2.8Staticmethodscanonlyusestaticattributes,instancemethodsuseboth.29

2.9MethodRaisingExceptions.30

2.10Methodcancallitself.31

2.11UseofMEinmethods.32

2.12PointerTables.33

2.13DynamicMethodCalls.34

2.14Useofparametertable.35

2.15UseofExceptionTable.36

3Constructors.37



3.1InstanceConstructorsgetfiredatthetimeofclassinstantiation.37

3.2InstanceConstructorscanhaveimportparameters.38

3.3Constructorscannothaveanyexportparameters.39

3.4InstanceConstructorscanraiseexceptions.40

3.5Useofstaticconstructor.41

3.6Staticconstructorcanbetriggeredatthebeginningofaprocessingblock(form/event/block/procedure)42

3.7Static/Classconstructorscannothaveanyinterface.43

4Inheritance.44

4.1Subclasscanaccesspublic/protectedcomponentsofsuperclass.44

4.2Subclasscanreimplementinheritedmethodsfromsuperclass.46

4.3Objectscannotbecreatedfromanabstractclass.47

4.4Abstractmethodscannotbeimplementedinabstractclass.48

4.5Finalclassescannothaveanysubclass.49

4.6Finalmethodscannotberedefinedinthesubclasses.50

4.7Staticattributesexistonlyonceperinheritancetree.51

4.8Constructorsofsuperclassflowsdownthechain.52

4.9Subclasscanhaveenhancedconstructorthanitssuperclass.53

4.10Staticconstructorofaclassiscalledonlyonceperprogram.55

4.11StatictypeandDynamictypeofavariable.56

4.12Statictypeshouldbemoregeneralthandynamictypeofareferencevariable.58

4.13Methodofaparentclass,usedfromitssubclass,usesattributesoftheparentclassonly,ifthemethodisnotredefinedinsubclass.59

4.14DemoonWideningCast.60

5Interface.61

5.1Simpleuseofaninterface.61



5.2Interfacescanonlybeimplementedinthepublicsectionofaclass.62

5.3Aclasswithaninterfaceshouldimplementallthemethodsofthatinterface.63

5.4Valuesforinterfaceattributesareassignedatthetimeofinclusioninaclass.64

5.5UseofFINALmethodsfromInterface.65

5.6UseofAbstractmethodsfromInterface.66

5.7UseofInterfaceReferenceVariable.67

5.8UseofNestedInterface.69

5.9UsingALIASES..70

5.10PolymorphismviaInterfaces.71

6Friendship.72

6.1FriendshipbetweenClasses.72

6.2Subclassesoffriendscanalsobecomefriends.73

6.3Friendshipisonesided.74

7Events.75

7.1EventswithHandlerMethodinthesameclass.75

7.2Eventwitheventhandlermethodindifferentclass.76

7.3Morethanoneeventhandlermethodcanexistforsameevent.77

7.4Useofstaticevent.79

7.5Eventswithexportparameters.80

8ClassBasedExceptions.81

8.1UsingSAPprovidedexceptionclass.81

8.2Whenbothsuperclassandsubclassareusedtotrackerror.82

8.3PropagationofClassBasedexceptionsinprocedurestothecaller.83

8.4ProgramcanraiseexceptionsbasedonSAPstandardexceptionclasses.84

8.5Objectsarecreatedfromexceptionclasseswhenerroristrapped.85



8.6DemoonLocallyDefinedExceptionClass.86

8.7NestedTRYENDTRYblock.87

8.8UseofCLEANUPsection.88

9BADIs(BusinessAddIns)89

9.1SingleImplementationofBADI.89

9.2MultipleImplementation.93

9.3SearchingforBADIinSAPTransactionandImplementingit.96

9.4MenuEnhancements.98

1Class

1.1Accessibilityofdifferentsectionsofaclass

Theme Fromthisprogram,onewilllearn:

1. Howtodefine,implementandinstantiateaclass.2. Whatarethedifferentsectionsofvisibilityinaclass.3. Howtodefineinstanceattributesandgetthemaccessedby

externalusers.

Thefollowingprogramwillalsoshowthat:

vDatadeclaredinpublicsectioncanbeaccessedbytheclassitself,byitssubclassesaswellasbyotherusersoutsidetheclass.

vDatadeclaredintheprotectedsectioncanbeaccessedbytheclassitself,andalsobyitssubclassesbutnotbyexternalusersoutsidetheclass.

vDatadeclaredintheprivatesectioncanbeaccessedbythe



vDatadeclaredintheprivatesectioncanbeaccessedbytheclassonly,butnotbyitssubclassesandbyexternalusersoutsidetheclass.

BriefDescription Thisprogramcontainsaclass:parentclasswithfollowingattributesindifferentsections:

Commondatainpublicsection

Protectdatainprivatesection

Privatedatainprivatesection

Themethodshowvalinclass:parentclassdisplaysvaluesofalltheattributes.

Thisdemonstratesthatclasscanaccessallitsattributes.

Classchildclassisasubclassofclassparentclass,whichhasamethod:subval.

Itdisplaysthevalueforthedata:commondataandprotectdata.

Then,itchangesthevaluesforbothanddisplaysthemagain.

Thisdemonstratesthatsubclasscanaccess/changepublic/protectedattributesofsuperclass.

IntheSTARTOFSELECTIONevent,object:parentisinstantiatedfromclass:parentclassandobject:childisinstantiatedfromclass:childclass.

Then,themethodshowvalofparent(objectofparentclass)andmethodsubvalofchild(objectofchildclass)iscalled,whichdisplaysthevaluesofdifferentattributes.

Then,thepublicattributeofobjectparentischangedandthechangedvalueisdisplayed.

Thisdemonstratesthatexternaluserscanchange/displaypublicattributesofaclass.

Dumpoftheprogram:



REPORTYSUBDELLINESIZE120.

CLASSparentclassDEFINITION.

PUBLICSECTION.

DATA:commondata(30)typecvalueAccessibletoall.

METHODS:SHOWVAL.

PROTECTEDSECTION.

DATA:protectdata(40)typecvalueProtecteddata.

privatesection.

data:privatedata(30)typecvaluePrivatedata.

ENDCLASS.

CLASSparentclassIMPLEMENTATION.

METHOD:SHOWVAL.

write:/5Alldatafromparentclassshown:.

write:/syuline.

WRITE:/5COMMONDATA,

/5PROTECTDATA,

/5PRIVATEDATA.

endmethod.

endclass.

CLASSchildclassDEFINITIONINHERITINGFROMparentclass.

PUBLICSECTION.

METHODS:subval.

ENDCLASS.

CLASSchildclassIMPLEMENTATION.

method:subval.



skip1.

write:/5Dataofparentshownfromchild.

write:/5syuline.

WRITE:/5COMMONDATA,

/5PROTECTDATA.

Commondata=Publicdatachangedinsubclass.

Protectdata=Protecteddatachangedinsubclass.

write:/5syuline.

WRITE:/5COMMONDATA,

/5PROTECTDATA.

endmethod.

endclass.

STARTOFSELECTION.

DATA:parenttypereftoparentclass,

childtypereftochildclass.

createobject:parent,

child.

callmethod:parent>showval,

child>subval.

skip2.

parent>commondata=Userchangingpublicdata.

write:/5parent>commondata.

Output Alldatafromparentclassshown:

Accessibletoall



Protecteddata

Privatedata

Dataofparentshownfromchild

Accessibletoall

Protecteddata

Publicdatachangedinsubclas

Protecteddatachangedinsubclass

Userchangingpublicdata

1.2Subclasscannotaccesstheprivatecomponentofsuperclass

Theme Theprogramdemonstratesthatsubclassescannotaccesstheprivatecomponentsofsuperclass.

Programdescription

Theprogramusedhereissimilartoabovewithchangeinthemethod:subvalofclass:childclass.Thismethodisnowattemptingtoaccesstheattribute:privatedata,whichisaprivateattributeofitssuperclass:parentclass.

Oncompilation,theprogramwillgiveacompilationerror.

Thisdemonstratesthatprivatecomponentsofsuperclasscannotbeaccessedbysubclasses.

ProgramDump

Takethefirstprogram.Onlychangethemethod:subvalofclass:childclassasfollows:

method:subval.

skip1.

write:/5Alldatafromparentclassshownbysubclass.



write:/5syuline.

WRITE:/5COMMONDATA,

/5PROTECTDATA,

/5privatedata.

endmethod.

Output Theprogramwillnotcompile.Itwillshowanerrormessage:

1.3Externaluserscannotaccessprotected/privatecomponentsofaclass

Theme Thisprogramwilldemonstratethatexternaluserscannotaccesstheprotectedandprivatecomponentsofaclass

ProgramDescription

Inthisprogram,classC1hasthreeattributesdeclaredindifferentsectionsasfollows:

vCommondatainpublicsection

vProtectdatainprivatesection

vPrivatedatainprivatesection

Inthemainprogram,anobject,OBJ1iscreatedfromclassC1andanincorrectattemptismadetodisplaytheprotectedandprivateattributeofclassC1usingitsobjectOBJ1.

Compilationofthisprogramproducesanerror.

Thisdemonstrates:protectedandprivatecomponentsofaclasscannotbeaccessedbyexternalusers.

Dump REPORTYSUBDELLINESIZE120.

CLASSc1DEFINITION.

PUBLICSECTION.



DATA:commondata(30)typecvalueAccessibletoall.

PROTECTEDSECTION.

DATA:protectdata(40)typecvalueProtecteddata.

privatesection.

data:privatedata(30)typecvaluePrivatedata.

ENDCLASS.

CLASSc1IMPLEMENTATION.

endclass.

STARTOFSELECTION.

DATA:obj1typereftoc1.

createobject:obj1.

write:/5obj1>protectdata,

obj1>privatedata.

Output Oncompilation,anerrorwillbegeneratedwhichwillprovethatprotectedandprivatecomponentsofaclasscannotbeaccessedbyexternalusers.

1.4LocalClasscanunderstanddataandtypesintheglobalareaoftheprogram.

Theme Thisprogramwilldemonstratethefollowing:

vDifferentattributesofaclasscanbeconstructedutilizingthedataandtypesdeclaredoutsidetheclass,intheglobalareaoftheprogram.

vDatadeclaredintheglobalareaoftheprogramcanbeuseddirectlyinaclass.



Programdescription

Theglobalsectionofthisprogramcontainsatype:TYP_TABandanintegervariable,NUM1.

ThesetypeanddataareusedwhiledefiningattributesL_NUM1(integer)andIT_TAB(internaltable)forclassC1.Also,theglobaldataL_NUMisuseddirectlyinsidetheprogram.

Thisdemonstratesthetheme.

Dump REPORTYSUBDEL1LINESIZE120.

TYPES:BEGINOFTYP_TAB,

NAME(15)TYPEC,

AGETYPEI,

ENDOFTYP_TAB.

DATA:num1typeivalue5.

CLASSc1DEFINITION.

publicsection.

methods:meth1.

DATA:l_numlikenum1,

it_tabtypestandardtableoftyp_tab,

w_tablikelineofit_tab.

ENDCLASS.


method:meth1.

data:l_cnum(2)typec.

l_num=0.

do5times.

l_num=l_num+1.

l_cnum=l_num.

concatenateStudent



l_cnum

intow_tabname.

w_tabage=num1*l_num.

appendw_tabtoit_tab.

clearw_tab.

enddo.

loopatit_tabintow_tab.

write:/5w_tabname,

w_tabage.

endloop.

endmethod.

endclass.

STARTOFSELECTION.

DATA:obj1typereftoc1.

createobject:obj1.

callmethodobj1>meth1.

Output Student15

Student210

Student315

Student420

Student525



1.5Classcanbeinstantiatedwithinimplementationofanotherclass

Theme Thisprogramwilldemonstratethatanobjectcanbecreatedfromaclass((whichwascreatedwithnoCREATEPRIVATE|PROTECTEDoptionatthetimeofitsdefinition)intheimplementationsectionofanotherclass.

ProgramDescription

ThisprogramcontainstwoclassesCLASS1andCLASS2.

ClassCLASS1containsmethod:METHOD1whichdisplaysvalueofsomeintegervariable.

ClassCLASS2containsmethod:METHOD2.Inthemethodimplementation,anobjectiscreatedfromclass:CLASS1andthenthatobjectisusedtocallmethodMETHOD1.

Thisdemonstratesthatobjectcanbecreatedfromaclass(CLASS1)withinimplementationsectionofanotherclass(CLASS2).

REPORTYSUBOOPS17.

classclass1definition.

publicsection.

methods:method1.

endclass.

classclass2definition.

publicsection.

methods:method2.

endclass.

classclass1implementation.

method:method1.

data:i_numtypeivalue2.

write:/5i_num.



endmethod.

endclass.

classclass2implementation.

method:method2.

data:obj1typereftoclass1.

createobjectobj1.

callmethodobj1>method1.

endmethod.

endclass.

startofselection.

data:my_objtypereftoclass2.

createobject:my_obj.

callmethodmy_obj>method2.

Output 2

1.6DeferredDefinitionofaClass

Theme Thisprogramwilldemonstratehowonecanrefertoaclasswithoutdefiningtheclassbeforethatpoint.But,theclasshastobedefinedlateron.

Programdescription

Inthisprogram,classC1hasaninterfacereferenceO2declaredwithreferencetoclassC2.But,beforethat,classC2isnotdefined.Itisdefinedlaterwithasinglepublicattribute,NUM.


Inthemainsectionoftheprogram,object:OBJ1iscreatedfromclassC1.



Then,anobjectiscreatedfromthereferencevariableO2inclassC1.Finally,theattributenumofthatobjectisdisplayed.

Dump reportysubdel1.

CLASSC2DEFINITIONDEFERRED.

CLASSC1DEFINITION.

PUBLICSECTION.

DATAO2TYPEREFTOC2.

ENDCLASS.

CLASSC2DEFINITION.

publicsection.

data:numtypeivalue5.

ENDCLASS.

startofselection.

data:obj1typereftoC1.

CREATEOBJECTobj1.

createobjectobj1>o2.

write:/5obj1>o2>num.

Output 5

1.7Placetoputnondeclarativestatements

Theme Foraclass,theIMPLEMENTATIONsectioncanimmediatelyfollowtheclassDEFINITIONsection.Ifthisisso,thenallthenondeclarativestatements(viz.,processingstatementsoutsideanyclassdefinition/implementation)shouldbeplacedunderaprocessingblock,suchas



STARTOFSELECTION.

Programdescription

ThisprogramcontainsaclassC1withamethodM1.

Inversion1,theIMPLEMENTATIONpartoftheclassfollowstheclassdefinitionsection.But,thenondeclarativestatementsarenotplacedunderanyblock.Thiscreatesacompilationerror.

Inversion2,thenondeclarativestatementsarenotplacedundertheblockSTARTOFSELECTION.Itgetscorrectlycompiled.


REPORTYSUBDEL.

classc1definition.

publicsection.

methods:m1.

endclass.

classc1implementation.

method:m1.

write:/5Iammethodm1.

endmethod.

endclass.

STARTOFSELECTION.

data:obj1typereftoc1.

createobjectobj1.

callmethodobj1>m1.

REPORTYSUBDEL.

classc1definition.

publicsection.

methods:m1.



endclass.


method:m1.

write:/5Iammethodm1.

endmethod.

endclass.


createobjectobj1.

callmethodobj1>m1.

Version1:IncorrectVersion2:Correct

Output Version1createscompilationerror.

Version2getscorrectlycompiled.

1.8UseofFieldSymbolsinClass

Theme FieldSymbolscanbeusedtocontainvalueofanyvariableinaclass.

ProgramDescription

Theprogramusesafieldsymbol,.Ithandlesthevaluesofinstanceattribute,inumandstaticattribute,onum.

Dump REPORTYSUB_ASSIGN_FS.

FIELDSYMBOLS:TYPEANY.

classc1definition.

publicsection.

*Instanceattribute:inumdeclaredbelow

data:inumtypeivalue5.



*staticattributeonumdeclaredbelow

classdata:onumtypeivalue10.

endclass.


endclass.

startofselection.

data:oref1typereftoc1.

createobjectoref1.

*Assigninginstanceattributetofieldsymbol

assignoref1>inumto.

write:/5.

*Assigningstaticattributetofieldsymbol

assignoref1>onumto.

write:/5.

assignc1=>onumto.

write:/5.

Output 5

10

10

1.9UseofStaticAttributes

Theme Thisprogramwilldemonstratethat:Staticsttributesofaclassareretainedthroughouttheentireruntime.Alltheobjectswithina



classcanaccessitsstaticattributes.

ProgramDescription

TheprogramcontainsaclassC1withstaticattribute:NUM.Themethod:M1incrementsthestaticattributeby1anddisplaysthevalueeachtimeitiscalled.

InthemainSTARTOFSELECTIONportion,twoobjects:OBJ1andOBJ2arecreatedfromclassC1.

First,staticattribute:NUMischangedandaccessedoutsidetheclassusingtheclasscomponentselector,=>.

Then,bothobjectsOBJ1andOBJ2areusedtocallmethod:M1whichshowsthenewvalueofstaticattribute:NUM.

ThatthevalueofthestaticattributegetsincrementedeachtimewhenthemethodM1ofdifferentobjectsiscalledshowsthatthisvariableisabletoretainitsvaluethroughtheentireruntime.

Dump reportysubdel.

CLASSc1DEFINITION.

PUBLICSECTION.

CLASSDATA:NUMTYPEI.

METHODS:M1.

ENDCLASS.


METHODm1.

num=num+1.

write:/5num.

ENDMETHOD.

ENDCLASS.

STARTOFSELECTION.

c1=>num=3.

write:/5c1=>num.

DATA:OREF1TYPEREFTOC1,



OREF2TYPEREFTOC1.

CREATEOBJECT:OREF1,

OREF2.

CALLMETHODOREF1>M1.

CALLMETHODOREF2>M1.

Output 3

4

5

1.10CreationofGlobalclassandusingitinalocalprogram

Theme Thisexamplewillshowyouhowtocreateaclassgloballyanduseitinyourlocalprogram

ProgramDescr.

Thereisademandtocreateaglobalclasswhichwillfurnishalistofmaterialsalongwiththeirdescriptionsbasedonthematerialtype.

GlobalclassZGET_MATERIALSwillbecreated.MethodLIST_MATERIALSwillbelongtothisclasswhichwilltakematerialtypeasaninputandwillfurnishalistofmaterialcodesandtheirdescriptionsbelongingtothatmaterialtype.

Steps Followthestepsoutlinedbelowtoperformthetask

Step1.CreatetheclassfromSE24:

vGototransactionSE24.



vEnterthenameoftheglobalclassyouwanttocreate,withYorZatthebeginning.

vPressCreatepushbutton.

vAdialogwindowshownabovewillappear.Checktheradiobutton:Class.

vPressEnter.

vAnotherdialogwindowshownabovewillappear.Enterthedescriptionfortheclass.

vSelectfromtheInstantiationlistboxwhetheryouwanttocreatetheclassasPUBLIC/PROTECTED/PRIVATE/ABSTRACT.

vChecktheradiobuttonforUsualABAPClass.

vCheckthecheckboxforFinal.

vPressSavepushbutton.

EnterthepackagenameorsaveitasLocalobject.

Step2:Createthemethod:LIST_MATERIALS

vGotothetabpage:Methods.

vEnterthedetailsforthemethodmentionname,typeofmethod(instance/static),inwhichvisibilitysectionthemethodwillresideandashortdescriptionofthemethod.

vCheckoff/uncheckthecheckboxtoensurethatthemethodwillbeimplemented.

ClickthepushbuttonforParameterstonavigatetothescreentoenterparametersforthemethod.

Therewillbeoneimportingparameter:L_MTARTandoneexportinginternaltable:MATERIAL_LIST.Createentriesforthemasshownabove.

Clickthepushbutton:ExceptionstomakeentryforExceptionstoberaisedbythemethod.

Enterthenameanddescriptionfortheexception.

Then,checkandactivatetheclass.



Step3:Writecodeformethodimplementation

Clickonthepushbutton:Code(bluecoloredbutton)toimplementthemethod.

AnABAPEditorwillopenup.Writethelogicforcodeimplementation.

Then,checkandactivatethecode.

Yourjobofcreatingaglobalclassiscomplete!!!

Step4:Usetheglobalclasscreatedbyyouinalocalprogram

REPORTYSUBDEL.

TYPES:BEGINOFtyp_mat,

matnrLIKEmaramatnr,

maktgLIKEmaktmaktg,

ENDOFtyp_mat.

DATA:it_matTYPESTANDARDTABLEOFtyp_mat,

x_matLIKELINEOFit_mat.

PARAMETERS:p_mtartLIKEmaramtartOBLIGATORY.

STARTOFSELECTION.

*Createobjectfromtheglobalclass

DATA:orefTYPEREFTOzget_materials.

CREATEOBJECToref.

*Callthemethodtogetlistofmaterialcodeandname

CALLMETHODoref>list_materials

EXPORTINGl_mtart=p_mtart

IMPORTINGmaterial_list=it_mat



EXCEPTIONS

material_not_found=2.

ifsysubrcne0.

write:/5Materialnotfound.

else.

*Displaythelist

loopatit_matintox_mat.

write:/5x_matmatnr,

x_matmaktg.

endloop.

endif.

Output Compileandruntheprogram.Therewillbeaparameterformaterialtypeintheselectionscreen.Enteravalidvalueandgetthelistofmaterialcodesanddescriptions.

2Methods

2.1Methodwithoneimportparameter/onlyonenonoptionalparameter

Theme Thisprogramwilldemonstratedifferentwaysofcallingamethodwhichhasonlyoneimportparameter.



Thisstrategyisalsovalidforcaseswhereamethodhasmorethanoneimportparameters,butonlyoneofthembeingnonoptional.

Program Thisprogramhasaclass,C1withamethod:meth1.Thismethodhasonlyoneimportparameter(input1).Lookatthemethodimplementationfordetails.Themainpurposeofthisprogramistodemonstratethedifferentwaysofcallingamethodwithsingleimportparameter.

Dump REPORTYSUBDEL.

CLASSC1DEFINITION.

PUBLICSECTION.

DATA:NUMTYPEIVALUE5.

METHODS:METH1IMPORTINGINPUT1TYPEI.

ENDCLASS.

CLASSC1IMPLEMENTATION.

METHOD:METH1.

num=NUM*INPUT1.

WRITE:/5NUM.

num=5.

ENDMETHOD.

ENDCLASS.

STARTOFSELECTION.

DATA:OREF1TYPEREFTOC1.

CREATEOBJECT:OREF1.

*Differentwaysofcallingthemethodwithoneimportparameter

CALLMETHODOREF1>METH1EXPORTINGINPUT1=4.

CALLMETHODOREF1>METH1(INPUT1=5).

CALLMETHODOREF1>METH1(6).



Output 20

25

30

2.2Importparameterspassedbyref.cantbechangedinsidethemethod.

Theme Parameterscanbepassedtoamethodasimportparametersintwofashion:

vByreference

vByvalue.

Parameterspassedbyvaluecanbechangedinternallyinamethod.But,parameterspassedbyreferencecannotbechangedinthemethod.

Programdescription

ThisprogramcontainsaclassC1withamethodMETH1.Thismethodcontainstwoinputparameters:

INPUT1:passedbyreference

INPUT2:passedbyvalue.

ThemethodMETH1attemptstochangeINPUT1.Oncompilation,anerrorisdisplayed.Thisestablishesthatinputparameterspassedbyreferencecannotbechangedwithinthemethod.

Dump REPORTYSUBDEL.

DATA:numTYPEI.

CLASSC1DEFINITION.

PUBLICSECTION.

METHODS:METH1IMPORTINGINPUT1TYPEI



value(input2)typei.

ENDCLASS.


METHOD:METH1.

Input1=4.

write:/5input1.

ENDMETHOD.

ENDCLASS.

STARTOFSELECTION.


CREATEOBJECT:OREF1.

num=3.

CALLMETHODOREF1>METH1EXPORTINGINPUT1=4

input2=num.

Output Oncompilation,anerrormessageisgenerated.

Now,insteadofchanginginput1,changetheimportparameterinput2(passedbyvalue)withinthemethod.Theprogramwillgetsuccessfullycompiledandexecuted.

2.3UseofPREFERREDPARAMETERinamethod

Theme IftherearemorethanoneOPTIONALimportparametersinamethodandnononoptionalimportparameterswithoutvalues,onecantypeintheclausePREFERREDPARAMETERafterthe



listofimportparameterstospecifywhichoftheoptionalparameterswillgetmorepreferencecomparedtootherswhenthemethodwillbecalledusingsyntax:CALLMETHODobjref>meth().

Inotherwords,itdecideswhichoftheoptionalparameterswillbeassignedthevalueVAL.

ProgramDescription

ThisprogramcontainsaclassC1containingmethodMETH1whichhastwooptionalparameters,INPUT1andINPUT2.Outofthem,parameterINPUT2isdeclaredaspreferredparameter.Themethodsimplydisplaysthevalueoftwoimportparameters.

Noticethelastlineoftheprogramandseetheoutput.TheoutputwillestablishthatthepreferredparameterINPUT2getsthevaluepassedtothemethodwhenitiscalledusingthesyntax:

CALLMETHODobjref>meth().

Dump REPORTYSUBDEL.

CLASSC1DEFINITION.

PUBLICSECTION.

METHODS:METH1IMPORTINGINPUT1TYPEIoptional

input2TYPEIOPTIONAL

PREFERREDPARAMETERINPUT2.

ENDCLASS.


METHOD:METH1.

write:/5input1,

/5input2.

ENDMETHOD.

ENDCLASS.

STARTOFSELECTION.




CREATEOBJECT:OREF1.

CALLMETHOD:OREF1>METH1(input1=5input2=3).

skip2.

write:/5Nextcall.

callmethodoref1>meth1(10).

Output 5

3

Nextcall

0

10

2.4UseofEXPORTandCHANGINGparametersofamethod

Theme ThisprogramwilldemonstratetheuseofEXPORTINGandCHANGINGparametersofamethod.

Programdescription

TheprogramcontainsamethodTAX_CALCbelongingtotheclassCTAX.ItreceivesGRADEasIMPORTINGparameterandSALARYasCHANGINGparameter.Basedonthegrade,theEXPORTINGparameterITAXiscalculatedandtheCHANGINGparameter,SALARYismodifiedbydeductingtaxfromit.

REPORTYSUBDEL.

DATA:w_taxtypepdecimals2,

w_salarytypepdecimals2.

CLASSCTAXDEFINITION.

PUBLICSECTION.

METHODS:TAX_CALCIMPORTINGgradeTYPEC



EXPORTINGitaxTYPEP

CHANGINGsalaryTYPEP.

ENDCLASS.

CLASSCTAXIMPLEMENTATION.

METHOD:TAX_CALC.

CASEgrade.

WHENA01.

itax=salary*0.2.

WHENA02.

itax=salary*0.1.

WHENOTHERS.

itax=salary*0.15.

ENDCASE.

salary=salaryitax.

ENDMETHOD.

ENDCLASS.

STARTOFSELECTION.

DATA:OREF1TYPEREFTOCTAX.

CREATEOBJECT:OREF1.

w_salary=30000.

w_tax=0.

write:/5Beforemethodcall,salaryandtaxare,

w_salary,

w_tax.

CALLMETHODOREF1>TAX_CALCEXPORTINGgrade=A01



IMPORTINGitax=w_tax

CHANGINGsalary=w_salary.

write:/5Aftermethodcall,salaryandtaxare,

w_salary,

w_tax.

Output Beforemethodcall,salaryandtaxare30,000.000.00

Aftermethodcall,salaryandtaxare24,000.006,000.00

2.5MethodusingInternalTableasoneoftheparameters

Theme Thisprogramdemonstrateshowaninternaltablecanbeusedasoneoftheinterfaceparametersofamethod.

ProgramDescription

Theprogramcontainsamethod:GETMARAinclass:GET_MATERIALS.Itacceptsmaterialgroup,MATGRasimportparameteranddetailsoutthedetailsofthematerialsbelongingtothatmaterialgroupintoI_TAB,whichisaninternaltableusedasEXPORTINGparameterforthemethod.

REPORTYSUBOOPS5.

types:beginoftyp_tab,

matnrlikemaramatnr,

meinslikemarameins,

endoftyp_tab.

data:itabtypestandardtableoftyp_tab,

x_tabLIKELINEOFITAB.

CLASSget_materialsDEFINITION.



PUBLICSECTION.

METHODS:getmaraIMPORTINGmatgrTYPEC

EXPORTINGl_tabTYPEANYTABLE.

endclass.

CLASSget_materialsIMPLEMENTATION.

METHOD:getmara.

SELECTmatnrmeinsINTOTABLEl_tab

FROMMARA

WHEREMATKL=matgr.

ENDMETHOD.

ENDCLASS.

PARAMETERS:p_matkllikemaramatkl.

STARTOFSELECTION.

DATA:w_matTYPEREFTOget_materials.

CREATEOBJECT:w_mat.

CALLMETHODw_mat>getmaraEXPORTINGmatgr=p_matkl

IMPORTINGl_tab=itab.

LOOPATITABINTOX_TAB.

WRITE:/5X_TABMATNR,X_TABMEINS.

ENDLOOP.

Output One/morethanonerecordswithmaterialnumberandbasicunit,dependingonthematerialgroupenteredintheselectionscreen.



2.6UseofRETURNINGparametersinmethod

Theme Togetsomevaluesfromamethod,onecanusetheEXPORTING,CHANGINGorRETURNINGparameters.

IfoneusesRETURNINGparameters,thefollowingrestrictionsapply:(1)NoEXPORTING/CHANGINGparameterscanbeusedforthemethod.

(2)OnlyoneRETURNINGparametercanbeused.

(3)RETURNINGparametersareonlypassedbyvalue.

ThisprogramdemonstratestheuseofRETURNINGparametersandthevariouswaystocallamethodwithRETURNINGparametertogetthevalueintosomevariable.

ProgramDescription

MethodM1inclassC1havetwoinputparameters(INPUT1andINPUT2),whichareusedtoderivevalueforRETURNINGparameter,RESULT.

Theprogramdemonstratesvarioussyntaxesthatcanbeusedtocallamethodofthiskind.

reportysubdel1messageid00.

data:w_numtypei.

classc1definition.

publicsection.

methods:m1importinginput1typei

input2typei

returningvalue(result)typei.

endclass.


method:m1.



result=input1*2+input2.

endmethod.

endclass.

startofselection.


createobjectobj1.

*Syntax1

callmethodobj1>m1EXPORTINGinput1=5

input2=4

RECEIVINGresult=w_num.

write:/5w_num.

*Syntax2

w_num=obj1>m1(input1=10input2=20).

write:/5w_num.

*Syntax3

moveobj1>m1(input1=2input2=3)tow_num.

write:/5w_num.

Output 14

40

7

2.7DemoonStaticMethod



Theme Thisprogramwillshowhowtodeclareanddefineastaticmethodandhowitcanbecalledusingclasscomponentselector.

Inthefollowingprogram,method:TESTMETHODisdefinedasstaticmethodandiscalledlaterusingclasscomponentselector,=>.

Dump REPORTYSUBOOPS19.

data:numtypei.

classtestclassdefinition.

publicsection.

classmethods:testmethod.

endclass.

classtestclassimplementation.

method:testmethod.

num=5.

write:/5num.

endmethod.

endclass.

startofselection.

callmethodtestclass=>testmethod.

Output 5

2.8Staticmethodscanonlyusestaticattributes,instancemethodsuseboth

Theme Staticmethodsofaclasscanonlyusestaticattributesofthatclass.Itcannotuseinstanceattributes.But,instancemethodscanuseboth.

Program ThefollowingprogramcontainsaclassC1whichcontainsthe



Description following:

Component Type Static/Instance

stnum Data static

Instnum Data Instance

Stmeth Method Static

Instmeth Method InstanceBoththestaticandinstancemethodsareattemptingtodisplayvaluesofthestaticandinstanceattributes:STNUMandINSTNUM.

Oncompilation,anerrorwillbegeneratedwhichwilldemonstratethatstaticmethodSTMETHcannotworkwithinstanceattribute,INSTNUM.

Dump REPORTYSUBDEL.

CLASSC1DEFINITION.

PUBLICSECTION.

CLASSDATA:STNUMTYPEIVALUE5.

DATA:INSTNUMTYPEIVALUE6.

CLASSMETHODS:STMETH.

METHODS:INSTMETH.

ENDCLASS.


METHOD:STMETH.

WRITE:/5STNUM.

WRITE:/5INSTNUM.

ENDMETHOD.

METHODINSTMETH.

WRITE:/5STNUM.



WRITE:/5INSTNUM.

ENDMETHOD.

ENDCLASS.

STARTOFSELECTION.


CALLMETHODc1=>stmeth.

CREATEOBJECTOREF1.

CALLMETHODoref1>instmeth.

Output Oncompilation,yougetthefollowingerror:

Removethelineinboldintheprogramandcompile.Itwillgetsuccessfullycompiledandexecuted.

2.9MethodRaisingExceptions

Theme Methodscanraiseexceptionslikefunctionmoduleswhichcanbehandledaftercallingthemethod,dependingonvarioussysubrcvalues.Thisprogramwilldemonstratethat.

Programdescription

Theprogramprovidestheuseraselectionscreenwheretheuserentersanumericvalue.Iftheuserentryis=5.Else,fivetimesofthevalueenteredisdisplayedbytheprogramonexecution.

TheclassC1inthisprogramcontainsmethodM1whichimportsvalueforNUM1,andreturnsfivetimesofitthroughtheexportparameter,NUM2.

However,ifthevaluepassedtoNUM1islesserthan5,itraisesanexceptionE1withsomeerrormessage.

ThemethodM1iscalledaftercreatinganobjectfromtheclass.User



ThemethodM1iscalledaftercreatinganobjectfromtheclass.Userenteredvalueintheparameterfield:P_NOispassedtoimportingparameterNUM1.

Dump reportysubdel1messageid00.

classc1definition.

publicsection.

methods:m1importingnum1typei

exportingnum2typei

exceptionse1.

endclass.


method:m1.

ifnum1lt5.

messagei398(00)withShouldbe>=5raisinge1.

else.

num2=num1*5.

endif.

endmethod.

endclass.

parameters:p_notypei.

startofselection.


createobjectobj1.

callmethodobj1>m1exportingnum1=p_no

importingnum2=p_no

exceptionse1=1.



IFsysubrc0.

MESSAGEIDSYMSGIDTYPESYMSGTYNUMBERSYMSGNO

WITHSYMSGV1SYMSGV2SYMSGV3SYMSGV4.

ELSE.

write:/5p_no.

ENDIF.

Output Theprogramprovidestheuseraselectionscreenwheretheuserentersanumericvalue.Iftheuserentryis=5.Else,fivetimesofthevalueenteredisdisplayedbytheprogramonexecution.

2.10Methodcancallitself

Theme Methodofaclasscancallitself.But,pleasedonotforgettospecifysomeexitpointtothemethod.Else,itwillcreateaninfiniteloop.

ProgramDescr.

TheprogramfollowingcontainsamethodM1inaclassC1.Itincreasesthevalueofstaticvariable,STATNUMby10anddisplaysit.Then,ifthevalueofSTATNUMis



ifstatnumgt100.

exit.

endif.

write:/5statnum.

callmethodm1.

endmethod.

endclass.

startofselection.


createobjectobj1.

callmethodobj1>m1.

Output 10

20

.

100

2.11UseofMEinmethods

Theme Amethodcanhaveavariabledefinedwithinithavingthesamenameasoneoftheattributesoftheclasstowhichthemethodbelongsto.

Toclearlyidentifytheclasslevelattribute,theselectorMEisused.

ProgramDescription

ClassTESTCLASScontainsmethodTESTMETHOD.ThereisavariableI_NUMdeclaredaspublicattributeintheclassaswellasin



theimplementationpartofthemethod.

ToaccessthevariableI_NUMattheclasslevelwithinthemethod,theselectorMEisused.Pleaseseetheouputsofthisprogramforbetterunderstanding.



publicsection.


methods:testmethod.

endclass.


method:testmethod.


write:/5me>i_num,accessvariableoftheclass

/5i_num.accessvariableofthemethod

endmethod.

endclass.

startofselection.

data:i_numtypei.

data:my_objtypereftotestclass.

createobject:my_obj.

callmethodmy_obj>testmethod.

Output 5

2



2.12PointerTables

Theme Thisprogramwilldemonstratetheuseofpointertables

ProgramDescription

Theprogrambelowusespointertable:MYOBJ_TAB.

REPORTYSUBOOPS19.


publicsection.

methods:testmethod.

classdata:numtypei.

endclass.


method:testmethod.

num=num+5.

write:/5num.

endmethod.

endclass.

startofselection.

data:myobjtypereftotestclass,

myobj_tabtypetableofreftotestclass.

do5times.

createobjectmyobj.

appendmyobjtomyobj_tab.

enddo.



loopatmyobj_tabintomyobj.

callmethod:myobj>testmethod.

endloop.

Output 5

10

15

20

25

2.13DynamicMethodCalls

Theme Onecancallmethodsdynamically.Followingrestrictionsapply:

vNameofthemethodcanbedynamicforstatic/instancemethod.

vNameoftheclasswhilecallingstaticmethodcanbedynamic.

vBoththenameofthestaticmethodandtheclasscontainingitcanbedynamic.

Whiledoingso,itisbettertouseuppercasetoassignthenameoftheclass/methodstothevariables(whichwillbeusedfordynamicassignment)

ProgramDescription

ThefollowingprogramcontainsclassC1withstaticmethod(STATM)anddynamicmethod(INSTM).Theprogramutilizesallthesyntaxestocallthesestatic/instancemethodsdynamically.


data:f(6)typec,

g(10)typec.



classc1definition.

publicsection.

classmethods:statm.

methods:instm.

endclass.


method:statm.

write:/5Iamstaticmethod.

endmethod.

method:instm.

write:/5Iaminstantmethod.

endmethod.

endclass.

startofselection.

data:oreftypereftoc1.

createobjectoref.

*Nameofinstancemethodcanbedynamic

f=INSTM.callmethodoref>(f).

*Nameofstaticmethodcanbedynamic

f=STATM.callmethodoref>(f).

*Nameoftheclasscanbedynamicforstaticmethodcall

f=C1.callmethod(f)=>statm.

*Nameofthemethodcanbedynamicforstaticmethodcall

f=STATM.callmethodc1=>(f).

*Bothcanbedynamicforstaticmethodcall



g=C1.callmethod(g)=>(f).

Output Iaminstantmethod

Iamstaticmethod

Iamstaticmethod

Iamstaticmethod

Iamstaticmethod

2.14Useofparametertable

Theme Fordynamicmethodcall,onecanusetheconceptofPARAMETERTABLEtoincludereferencesofallinterfaceparametersofthemethod(insteadofmentioningthemseparately).

Prog.

Descr.

TheprogramcontainsclassC1withamethodM1.ThismethodhasoneIMPORTINGparameter,P1andoneEXPORTINGparameterP3.

P3iscalculatedwithinthemethod.

Here,parametertablePTABisusedtodynamicallycallthemethodM1.

Pleasenotethat,parametertablesworkonlywhenamethodiscalleddynamically(i.e.today,thenameofthemethod/classisdeterminedatruntime).


DATA:i_resulttypei,

i_numtypeivalue5.

DATAf(2)TYPEcVALUEM1.

CLASScl_abap_objectdescrDEFINITIONLOAD.

DEFINE:poptable.

ptab_linename=&1.



ptab_linekind=CL_ABAP_OBJECTDESCR=>&2.

GETREFERENCEOF&3INTOptab_linevalue.

INSERTptab_lineINTOTABLEptab.

IFsysubrcne0.

EXIT.

ENDIF.

ENDOFDEFINITION.

CLASSc1DEFINITION.

PUBLICSECTION.

METHODSm1IMPORTINGp1TYPEi

exportingp3typei.

ENDCLASS.


METHODm1.

p3=p1+200.

ENDMETHOD.

ENDCLASS.

DATArTYPEREFTOc1.

DATA:ptabTYPEabap_parmbind_tab,

ptab_lineLIKELINEOFptab.

STARTOFSELECTION.

poptable:P1EXPORTINGi_num,

P3IMPORTINGi_result.

CREATEOBJECTrTYPEc1.

CALLMETHODr>(f)PARAMETERTABLEptab.



write:/5i_result.

Output 205

2.15UseofExceptionTable

Theme Insteadofdealingwitheachandeveryexceptionandassigningittodifferentsysubrcvalues,onecanuseexceptiontabletohandletheexceptionswhenamethodiscalleddynamically.

TheclassC1containsmethodM1whichraisesanexception.ExceptiontableETABisusedtohandletheexception.

REPORTYSUBOOPS25.

CLASScl_abap_objectdescrDEFINITIONLOAD.

CLASSc1DEFINITION.

PUBLICSECTION.

METHODSm1EXCEPTIONSexc.

ENDCLASS.


METHODm1.

RAISEexc.

ENDMETHOD.

ENDCLASS.

DATArTYPEREFTOobject.

DATAf(3)TYPEcVALUEM1.

DATA:etabTYPEabap_excpbind_tab,

etab_lineLIKELINEOFetab.

STARTOFSELECTION.



etab_linename=EXC.

etab_linevalue=4.

INSERTetab_lineINTOTABLEetab.

IFsysubrcne0.

EXIT.

ENDIF.

CREATEOBJECTrTYPEc1.

CALLMETHODr>(f)EXCEPTIONTABLEetab.

WRITEsysubrc.

Output 4

3Constructors

3.1InstanceConstructorsgetfiredatthetimeofclassinstantiation

Theme Thissimpleprogramwillshowyouthatinstanceconstructormethodsofaclassgettriggeredwhenanobjectiscreatedfromtheclass.

ProgramDescription

ThisprogramcontainsaclassC1withaconstructormethodwhichwritesoutsomethingtoindicatethatitistriggered.IntheSTARTOFSELECTIONblock,theclassC1isinstantiated,whichtriggerstheinstanceconstructormethod(asisevidentbytheoutputasreport).

Thisestablishesthetheme.




CLASSC1DEFINITION.

PUBLICSECTION.

METHODS:CONSTRUCTOR.

ENDCLASS.


METHODconstructor.

WRITE:/5Iamconstructor.

skip2.

ENDMETHOD.

ENDCLASS.

***************mainprogram**************

STARTOFSELECTION.

DATA:obj1TYPEREFTOc1.

CREATEOBJECT:obj1.

Output Iamconstructor

3.2InstanceConstructorscanhaveimportparameters

Theme Instanceconstructorscanhaveimportparameters.ValuestothemarepassedatthetimeofCREATEOBJECTstatementtocreateobjectfromtheclasscontainingtheconstructor.

ProgramDescription

TheprogramcontainsaclassC1whichhasoneinstanceconstructorwithoneimportparameter.TheconstructorgetsfiredatthetimeofCREATEOBJECTstatement.




CLASSc1DEFINITION.

PUBLICSECTION.

METHODS:CONSTRUCTORimportingtodaytyped.

ENDCLASS.


METHODconstructor.

Write:/5Todayis:,todaydd/mm/yyyy.

ENDMETHOD.

ENDCLASS.

***************mainprogram**************

STARTOFSELECTION.


CREATEOBJECT:obj1exportingtoday=sydatum.

Output Todayis08.04.2004

3.3Constructorscannothaveanyexportparameters

Theme Thisprogramwilldemonstratethatconstructormethodscannothaveanyexportparameters

ProgramDescription

Thisprogramattemptstocreateaconstructorwithexportparameter,whichistrappedandresistedatthetimeofcompilation.





CLASSc1DEFINITION.

PUBLICSECTION.

METHODS:CONSTRUCTORexportingnametypec.

ENDCLASS.

Output Compilationerrrorisreported.

3.4InstanceConstructorscanraiseexceptions

Theme InstanceConstructormethodscanraiseexceptions

ProgramDescriptions

ThisprogramcontainsaclassC1whichcontainsaninstanceconstructormethod.Itacceptsanimportparameter,NUM.Ifitislesserthan7,anexceptionisraised,whichisproperlyhandledbyspecifyingsomesysubrcvalueatthetimeofCREATEOBJECTstatementandlaterhandledproperly.


CLASSc1DEFINITION.

PUBLICSECTION.

METHODS:CONSTRUCTORimportingnumtypei

exceptionse1.

ENDCLASS.


METHODconstructor.

ifnumlt7.

raisee1.

endif.



ENDMETHOD.

ENDCLASS.

***************mainprogram**************

STARTOFSELECTION.


CREATEOBJECT:obj1exportingnum=5

exceptionse1=2.

ifsysubrc=2.

write:/5Exceptionsraised.

endif.

Output ExceptionsRaised

3.5Useofstaticconstructor.

Theme Therearetwoprogramsoverherewhichwillshowyousimpleexampleonastaticconstructor.Youwilllearnhowtodeclareastaticconstructor.Static/classconstructorsgettriggeredbeforeanyofthefollowingevents:

vGeneratinganinstanceofaclassusingCREATEOBJECTobj(),whereobjhasthedatatypeREFTOclass.

vCallingastaticmethodusing[CALLMETHOD]class=>meth().

vRegisteringastaticeventhandlermethodusingSETHANDLERclass=>methforobj().

vRegisteringaneventhandlermethodforastaticevent()oftheclassclass.

vAddressingastaticattribute()withclass=>a.

Thesetwoprogramswillshowyouthataclassconstructorgetsfired



Thesetwoprogramswillshowyouthataclassconstructorgetsfiredbeforeanyofitsstaticcomponentsareaccessed,oranobjectiscreatedfromtheclass.


CLASSc1DEFINITION.

PUBLICSECTION.

CLASSDATA:NUMTYPEIVALUE5.

CLASSMETHODS:CLASS_CONSTRUCTOR.

ENDCLASS.


METHODCLASS_CONSTRUCTOR.

WRITE:/5Iamclassconstructor.

ENDMETHOD.

ENDCLASS.

STARTOFSELECTION.

DATA:OREFTYPEREFTOC1.

CREATEOBJECTOREF.

REPORTYSUBOOPS2.

CLASSc1DEFINITION.

PUBLICSECTION.





ENDCLASS.




ENDMETHOD.

ENDCLASS.

STARTOFSELECTION.

WRITE:/5C1=>NUM.

ConstructoristriggeredwhenastaticConstructorisfiredwhenanobjectis

attributeisaccessedcreatedfromtheclass

Output Forthefirstprogram(ontheLHS):

Iamclassconstructor

5

Forthesecondprogram(ontheRHS):

Iamclassconstructor

3.6Staticconstructorcanbetriggeredatthebeginningofaprocessingblock(form/event/block/procedure)

Theme IntheSTARTOFSELECTIONblockofthisprogram,staticattributeofaclasscontainingclassconstructorwillbeaccessed.Thiswilldemonstratethatthethefirstthingwhichwillgetexecutedinthe



STARTOFSELECTIONblockistheclassconstructormethod,irrespectiveofthepointatwhichthestaticattributeisaccessed.

ProgramDescription

TheprogramcontainsaclassC1withastaticconstructor,whichprintsthestatement:Iamclassconstructor.

Thisclassalsocontainsastaticattribute,numofvalue=5.

TheSTARTOFSELECTIONblockinthisprogramcontainsthefollowingstatements:

Awritestatementwhichwillprint:Hello

Acalltoaccessthestaticattribute(NUM)ofclassC1.

Onexecutionofthisprogram,wewillgetthefollowingoutputinthelist:

Iamclassconstructor

Hello

5

insteadoftheexpectedoutput:

Hello

Iamclassconstructor

5



CLASSc1DEFINITION.

PUBLICSECTION.



ENDCLASS.






ENDMETHOD.

ENDCLASS.

STARTOFSELECTION.

write:/5Hello.

write:/5c1=>num.

Output Iamclassconstructor

Hello

5

3.7Static/Classconstructorscannothaveanyinterface

Theme Thisprogramwillshowyouthatstaticconstructorsofaclasscannothaveanyinterfaceparametersandexceptions

ProgramDescription

Inthisprogram,theclassC1containsaclassconstructorwhichishavinganimportparameter,NUM.Theprogramcouldnotbesuccessfullycompiledduetosuchattempt.


CLASSc1DEFINITION.

PUBLICSECTION.

CLASSMETHODS:CLASS_CONSTRUCTORIMPORTINGNUMTYPEC.

ENDCLASS.

Output Compilationoftheprogranwillfailwithanerrormessage:



ThemethodCLASS_CONSTRUCTORmaynothaveparametersorEXCEPTIONS.

4Inheritance

4.1Subclasscanaccesspublic/protectedcomponentsofsuperclass

Theme Thisprogramwilldemonstrate:

vHowtocreateasubclassfromasuperclass.

vSubclasscanaccesspublic/protectedcomponents(methods,attributesetc)ofsuperclass.

Prog.Descr.

ThisprogramcontainssuperclassC1anditssubclassC2.ClassC1hasthefollowingcomponents:

Component Nature SectionofExistence

Significance/action

NUM Attribute public Value=6

METH1 Method Public DisplaysvalueofNUM

METH2 Method Protected Displays:Iammeth2

NUM2 Attribute Protected Value=7SubclassofC1isC2whichcontainsthefollowingnewcomponents:

Component Nature SectionofExistence

Significance/action

M1 Method public Callsmethodmeth1.Callsmethodmeth2Displaysvalueofvariablenum2.



IntheSTARTOFSELECTIONblock,anobjectOREFiscreatedfromC2andthemethodM1iscalled.TheoutputoftheprogramshowsthatmethodM1ofclassC2callsmethodMETH1,thenMETH2andfinallydisplaysvariableNUM2.

ThisdemonstratesthatsubclassC2hasaccesstothepublicandprotectedmethodsandattributesofsuperclassC1andtrulyestablishesthetheme.

Dump REPORTYSUBDEL.

CLASSC1DEFINITION.

PUBLICSECTION.

METHODS:METH1.

DATA:NUMTYPEIVALUE6.

PROTECTEDSECTION.

DATA:num2typeivalue7.

METHODSMETH2.

ENDCLASS.


METHOD:METH1.

WRITE:/5num.

endmethod.

METHOD:METH2.

WRITE:/5Iammeth2.

ENDMETHOD.

ENDCLASS.

CLASSC2DEFINITIONINHERITINGFROMC1.

PUBLICSECTION.

METHODS:M1.



ENDCLASS.


METHODM1.

CALLMETHOD:meth1,meth2.

write:/5num2.

endmethod.

endclass.

STARTOFSELECTION.

DATA:OREFTYPEREFTOC2.

CREATEOBJECTOREF.

CALLMETHOD:OREF>M1.

Output 6

Iammeth2

7

4.2Subclasscanreimplementinheritedmethodsfromsuperclass

Theme Subclasscanreimplementtheinheritedpublicandprotectedmethodsfromsuperclass.

ProgramDescr.

ClassC1containsmethodMETH1(public)andMETH2(protected),bothofwhicharemodifiedandreimplementedinitssubclassC2.ObjectsarecreatedoutofbothclassesandthemethodMETH1forbothobjectsarecalled.

Outputoftheprogramdemonstratesdifferentbehaviourformethod



OutputoftheprogramdemonstratesdifferentbehaviourformethodMETH1ofclassC1andC2.


Dump REPORTYSUBDEL.

CLASSC1DEFINITION.

PUBLICSECTION.

METHODS:METH1.

PROTECTEDSECTION.

METHODSMETH2.

ENDCLASS.


METHOD:METH1.

WRITE:/5Iammeth1inclassC1.

CALLMETHODMETH2.

ENDMETHOD.

METHOD:METH2.


ENDMETHOD.

ENDCLASS.


PUBLICSECTION.

METHODS:METH1redefinition.

PROTECTEDSECTION.

METHODS:METH2redefinition.

ENDCLASS.




METHODMETH1.


callmethodmeth2.

endmethod.

METHOD:METH2.


ENDMETHOD.

endclass.

STARTOFSELECTION.


OREF2TYPEREFTOC2.

CREATEOBJECT:OREF1,OREF2.

CALLMETHOD:OREF1>METH1,

OREF2>METH1.

Output Iammeth1inclassC1

Iammeth2inclassC1

Iammeth1inclassC2

Iammeth2inclassC2

4.3Objectscannotbecreatedfromanabstractclass.

Theme Objectscannotbecreatedfromanabstractclass.Onlythesubclassesofsuchclasscanbeinstantiated.

Program ThisprogramcontainsanabstractclassC1anditssubclassC2.Object



Description cannotbecreatedfromclassC1,butpossiblefromclassC2.

Dump REPORTYSUBDEL.

CLASSC1DEFINITIONABSTRACT.

PUBLICSECTION.

ENDCLASS.


METHOD:METH1.

ENDCLASS.


ENDCLASS.


endclass.

STARTOFSELECTION.

data:OREF1TYPEREFTOC1,

OREF2TYPEREFTOC2.

CREATEOBJECToref2.

REPORTYSUBDEL.


PUBLICSECTION.

ENDCLASS.


METHOD:METH1.

ENDCLASS.




ENDCLASS.


endclass.

STARTOFSELECTION.

data:OREF1TYPEREFTOC1,

OREF2TYPEREFTOC2.

CREATEOBJECToref1.

InstantiationofabstractclassInstantiationofsubclassofanabstractclass

Output Instantiationofabstractclasswillberesistedwitherrormessageatthetimeofcompilation.

Instantiationofsubclassofanabstractclasswillbeallowed.

4.4Abstractmethodscannotbeimplementedinabstractclass

Theme Abstractmethodscannotbeimplementedinthatclass.Ithastobeimplementedinoneofitssubclass.Toimplementanabstractmethodinasubclass,oneneedtoredefinethissubclassusingtheREDEFINITIONaddition.

ProgramDescr.

ThisprogramcontainsanabstractclassC1withabstractmethodMETH1,whichisimplementedinthesameclass.Theprogramwillnotbecompiledduetothis.

Theprogramisthenmodifiedandtheabstractmethodisimplementedin



TheprogramisthenmodifiedandtheabstractmethodisimplementedinclassC2,subclassofC1.Now,theprogramgetssuccessfullycompiled.

DumpIncorrect Correct

REPORTYSUBDEL.


PUBLICSECTION.

METHODS:METH1ABSTRACT.

ENDCLASS.


METHOD:METH1.

WRITE:/5Iammethod:METH1.

ENDMETHOD.

ENDCLASS.


ENDCLASS.


endclass.

STARTOFSELECTION.

data:OREF2TYPEREFTOC2.

CREATEOBJECToref2.

REPORTYSUBDEL.

CLASSC1DEFINITION




PUBLICSECTION.

METHODS:METH1ABSTRACT.

ENDCLASS.


ENDCLASS.


publicsection.

methods:meth1redefinition.

ENDCLASS.


METHOD:METH1.

WRITE:/5Iammethod:METH1.

ENDMETHOD.

endclass.

STARTOFSELECTION.


CREATEOBJECToref2.



4.5Finalclassescannothaveanysubclass

Theme SubclassescannotbeinheritedfromafinalClass.Theycanonlybeinstantiated.

ProgramDescrip.

ThisprogramcontainsafinalclassC1andasubclassC2.Thisisnotallowedandisresistedatthetimeofcompilation.

Hence,thethemeisproperlyestablished.

Dump REPORTYSUBDEL.

CLASSC1DEFINITIONFINAL.

ENDCLASS.


ENDCLASS.


ENDCLASS.


endclass.

STARTOFSELECTION.


CREATEOBJECToref2.

Output Compilationerrorisgenerated:

ThefinalclassC1cannothaveanysubclasses.



4.6Finalmethodscannotberedefinedinthesubclasses

Theme Finalmethodinaclasscanonlybedefinedinthatclass.Itcannotberedefinedinanyofitssubclasses.

ProgramDescr.

ThisprogramcontainsaclassC1whichhasafinalmethod:METH1.

ClassC2issubclassofC1andtriestoredefinethefinalmethod.

Compilationerrorisgenarated,resistingsuccessfulcompilation.


Dump REPORTYSUBDEL.

CLASSC1DEFINITION.

PUBLICSECTION.

METHODS:METH1FINAL.

ENDCLASS.


methodmeth1.

write:/5Iammethodmeth1.

endmethod.

ENDCLASS.


PUBLICSECTION.

methods:meth1redefinition.

ENDCLASS.




method:meth1.

write:/5Iammeth1,modifiedinclassC2.

Endmethod.

endclass.

STARTOFSELECTION.


CREATEOBJECToref2.

Output Programisnotsuccessfullycompiled.Thecompilationerrormessageisasfollows:

ThefinalmethodMETH1cannotberedefined.

4.7Staticattributesexistonlyonceperinheritancetree

Theme Staticattributesonlyexistonceineachinheritancetree.Onecanchangethemfromoutsidetheclassusingtheclasscomponentselectorwithanyclassname,orwithinanyclassinwhichtheyareshared.Theyarevisibleinallclassesintheinheritancetree.

ProgramDescr.

ClassC1containsstaticattribute,NUM.

ClassC2andC3aresubclassesofclassC1.

IntheSTARTOFSELECTIONblock,thestaticattribute,NUMischangedusingreferenceofclassC3.

ItgetschangedwithreferencetoclassC2also.

Hence,staticattribute,NUM,changedviaclassC3isalsochangedwithrespecttoC2also.Thisdemonstratesthetheme.

Dump REPORTYSUBDEL.



CLASSC1DEFINITION.

PUBLICSECTION.

classdata:numtypei.

ENDCLASS.


ENDCLASS.


ENDCLASS.


endclass.


ENDCLASS.

STARTOFSELECTION.

C3=>NUM=10.

WRITE:/5C2=>NUM.

Output 10

4.8Constructorsofsuperclassflowsdownthechain

Theme Constructorofsuperclassisinheritedbythesubclassalso.

ProgramDescr.

ClassC1containsaconstructormethod,butitssubclassC2doesnotexplicitlyhaveitsown.

WhenobjectfromclassC2iscreated,theconstructorofclassC1istriggered.





CLASSC1DEFINITION.

PUBLICSECTION.


ENDCLASS.


METHODconstructor.

WRITE:/5IamC1.

skip.

ENDMETHOD.

ENDCLASS.


ENDCLASS.


ENDCLASS.

STARTOFSELECTION.

DATA:objtypereftoC2.

CREATEOBJECT:obj.

Output IamC1.

4.9Subclasscanhaveenhancedconstructorthanitssuperclass.



Theme Asubclasscanmodifytheconstructormethodandaddsomeextrafunctionalities.Intheinstanceconstructormethodofthechildclass,theoneforthesuperclassshouldbecalledfirstusing:

CALLMETHODsuper>CONSTRUCTORstatementandthenadditionalstatementscanbeadded.

Pl.notethatREDEFINITIONstatementisnotrequiredtoenhanceconstructorsforasubclass.

ProgramDescrip.

Thisprogramcontainsthreeclasses:

vGRANDFATHERatthetopofthenodewithitsownconstructormethod

vFATHER,subclassofGRANDFATHERwithenhancedconstructor

vSON,subclassofFATHERwithitsownenhancedconstructor.

AnobjectiscreatedfinallyfromtheclassSON,whichtriggerstheconstructormethodsintheorder:GRANDFATHERFATHERSON.

REPORTYSUBOOPS18.

CLASSgrandfatherDEFINITION.

PUBLICSECTION.


ENDCLASS.

CLASSgrandfatherIMPLEMENTATION.

METHODconstructor.

WRITE:/5Iamgrandfather.

skip.

ENDMETHOD.

ENDCLASS.

CLASSfatherDEFINITIONINHERITINGFROMGRANDFATHER.

publicsection.




ENDCLASS.

CLASSfatherIMPLEMENTATION.

METHODconstructor.

callmethodsuper>constructor.

WRITE:/5Iamfather.

skip.

ENDMETHOD.

ENDCLASS.

CLASSsonDEFINITIONINHERITINGFROMFATHER.

publicsection.


ENDCLASS.

CLASSsonIMPLEMENTATION.

METHODconstructor.

callmethodsuper>constructor.

WRITE:/5Iamson.

skip.

ENDMETHOD.

ENDCLASS.

STARTOFSELECTION.

DATA:mysontypereftoson.

CREATEOBJECT:myson.

Output Iamgrandfather

Iamfather



Iamson

4.10Staticconstructorofaclassiscalledonlyonceperprogram.

Theme Thefirstwhenasubclassinaprogramisaccessed,itsstaticconstructorisexecuted.But,beforeitcanbeexecuted,thestaticconstructorsofallofitssuperclassesmustalreadyhavebeenexecuted.Astaticconstructormayonlybecalledonceperprogram.Therefore,whenonefirstaddressasubclass,thesystemlooksforthenexthighestsuperclasswhosestaticconstructorhasnotyetbeenexecuted.Itexecutesthestaticconstructorofthatclass,followedbythoseofallclassesbetweenthatclassandthesubclassthatisaddressed.

ProgramDescr.

Thisprogramcontainsthreeclasses:

vFATHERwithitsownstaticconstructormethod

vSON,subclassofFATHERwithitsownstaticconstructormethod.

AnobjectiscreatedfinallyfromtheclassSON,whichtriggerstheconstructormethodsintheorder:FATHERSON.

Now,anobjectiscreatedfromtheclassFATHER.But,thatdidnottriggerconstructorofclassFATHER,becausethathadalreadybeentriggeredbytheprogramwhenanobjectwascreatedfromtheclassSON.



CLASSfatherDEFINITION.

publicsection.

classMETHODS:class_CONSTRUCTOR.

ENDCLASS.



CLASSfatherIMPLEMENTATION.

METHODclass_constructor.

WRITE:/5Iamfather.

skip.

ENDMETHOD.

ENDCLASS.

CLASSsonDEFINITIONINHERITINGFROMFATHER.

publicsection.

classMETHODS:class_CONSTRUCTOR.

ENDCLASS.

CLASSsonIMPLEMENTATION.

METHODclass_constructor.

WRITE:/5Iamson.

skip.

ENDMETHOD.

ENDCLASS.

STARTOFSELECTION.

DATA:mysontypereftoson.

CREATEOBJECT:myson.

data:myfathertypereftofather.

createobject:myfather.

Output Iamfather

Iamson



4.11StatictypeandDynamictypeofavariable

Theme Statictypeofareferencevariablecanpointtoasuperclass;whereasitsdynamictypecanpointtooneofitssubclasses.

Thisprogramwillshowyouvariouswaystodothat.

ProgramDescrip.

ThisprogramcontainsclassC1withmethodM1.ClassC2isasubclassofC1andcontainsredefinedimplementationofmethodM1.

Referencevariablesarecreatedintheprogramasfollows:

ReferenceVariable

Statictype

Dynamictype

Dynamictypeassignedby

OREF1 C1 C1 CREATEobjectoref1.

OREF11 C1 C2 CREATEOBJECToref11TYPEC2.

OREF111 C1 C2 CREATEOBJECTOREF111.

OREF111=OREF2.

OREF2 C2 C2 CREATEOBJECToref2.Finally,methodM1iccalledusingallobjects.Theobservationsareasfollows:

Methodcall

Callsmethod Reason

OREF1>M1 M1ofclassC1.

BothStatic&DynamictypeofOREF1referstoC1.

OREF11>M1

M1ofclassC2.

StatictypeofOREF11referstoC1,dynamictypetoC2.

OREF111>M1

M1ofclassC2.

StatictypeofOREF111referstoC1,dynamictypetoC2.

OREF2>M1 M1ofclassC2 BothStatic&DynamictypeofOREF2referstoC2.




classc1definition.

publicsection.

methods:m1.

endclass.


methodm1.

write:/5Iamm1ofc1.

endmethod.

endclass.

classc2definitioninheritingfromc1.

publicsection.

methods:m1redefinition.

endclass.


methodm1.

write:/5Iamm1ofc2.

endmethod.

endclass.

STARTOFSELECTION.


OREF11TYPEREFTOC1,

OREF111TYPEREFTOC1,

OREF2TYPEREFTOC2.

CREATEOBJECT:OREF1,



OREF11TYPEC2,

OREF111,

OREF2.

OREF111=OREF2.

CALLMETHOD:OREF1>M1,Output:Iamm1ofc1

OREF11>M1,Output:Iamm1ofc2

OREF111>M1,Output:Iamm1ofc2

OREF2>M1.Output:Iamm1ofc2

Output Iamm1ofc1

Iamm1ofc2

Iamm1ofc2

Iamm1ofc2

4.12Statictypeshouldbemoregeneralthandynamictypeofareferencevariable

Theme Statictypeofareferencevariablecanrefertoasuperclass,whereasitsdynamictypecanrefertoasubclassofthesuperclass.Inthatcase,thereferencevariablewillidentifyallthecommoncomponentsofthesuperclassandsubclass.Itwillnotbeabletoidentifyanynewcomponentsinthesubclass,whicharenotpresentinitssuperclass.

ProgramDescr.

ThisprogramcontainsclassC1anditssubclassC2.

ClassC1containsmethodM1,whichisalsoredefinedinclassC2.

ClassC2containsanewmethodM2.

AreferencevariableOREF11iscreatedwithstatictypeofC1anddynamictypeofC2.



MethodM2isattemptedtobecalledusingOREF11.

Thisproducescompilationerror,establishingthetheme.


classc1definition.

publicsection.

methods:m1.

endclass.


methodm1.

write:/5Iamm1ofc1.

endmethod.

endclass.


publicsection.

methods:m1redefinition.

methods:m2.

endclass.


methodm1.

write:/5Iamm1ofc2.

endmethod.

methodm2.

write:/5Iamm2.

endmethod.

endclass.



STARTOFSELECTION.


CREATEOBJECT:OREF11TYPEC2.

CALLMETHOD:OREF11>M2.

Output CompilationerrorfailstoidentifymethodM2inthelaststatementoftheprogram.

4.13Methodofaparentclass,usedfromitssubclass,usesattributesoftheparentclassonly,ifthemethodisnotredefinedinsubclass.

Theme Aslongasamethod(usingprivateattributes)inheritedfromasuperclassisnotredefined,itstillusestheprivateattributesofthesuperclass,notthoseofthesubclass,evenifthesubclasshasprivateattributesofthesamename.

ProgramDescrip.

ClassC1containsamethodM1inthepublicsectionandaprivatevariable,NUMofvalue=5.MethodM1inclassC1displaysthevalueofprivatevariable,NUM.

ClassC2isasubclassofclassC1.ItdoesnotredefinemethodM1.But,ithasalsoaprivatevariable,NUMwithvalue=6.

AnobjectiscreatedfromclassC2andthemethodM1iscalled.

TheoutputshowsthatthevariableNUM(asdisplayedbymethodM1)hasbeentakenfromclassC1,notC2.


Dump reportysubdel.

CLASSc1DEFINITION.

PUBLICSECTION.



METHODS:m1.

PRIVATESECTION.

DATA:numTYPEIVALUE5.

ENDCLASS.


METHOD:m1.

write:/5num.

ENDMETHOD.

ENDCLASS.

CLASSc2DEFINITIONINHERITINGFROMc1.

PUBLICSECTION.

DATA:numTYPEIVALUE6.

ENDCLASS.


ENDCLASS.

STARTOFSELECTION.

DATA:oref2TYPEREFTOc2.

CREATEOBJECT:oref2.

CALLMETHODoref2>m1.

Output 5

4.14DemoonWideningCast

Theme Thisprogramwillshowtheuseofwideningcastoperator



ProgramDescription

ClassC1issuperclassofC2.ObjectofclassC2isassignedtheobjectofclassC1usingwideningcastoperator.Thishelpstoavoidthecompilationerror,butgenaratestheerrorcx_sy_move_cast_errortrappedatruntime,whichishandledandreportedproperlyintheprogram.

Dump REPORTYSUBDEL.

classc1definition.

publicsection.

data:numtypeivalue5.

endclass.


endclass.


publicsection.

endclass.


endclass.

startofselection.

data:obj1typereftoc1,

obj2typereftoc2.

createobject:obj1,

obj2.

TRY.

obj2?=obj1.

CATCHcx_sy_move_cast_error.

write:/5cx_sy_move_cast_errortrapped.

ENDTRY.



Output cx_sy_move_cast_errortrapped

5Interface

5.1Simpleuseofaninterface

Theme Thisprogramwillshowsimpleuseofaninterfacewithitsowndataandmethodsandhowitisimplementedinaclass.Itwillalsoshowthattherecanbemethodsofsamenameforaninterfaceandtheclassimplementingtheinterface.

ProgramDesc

ThisprogramcontainsaninterfaceI1withattribute:NUManmethod:METH1.

Thisinterfaceisimplementedinaclass:C1whichalsohasitsownmethodMETH1.

AnobjectOREFiscreatedfromclassC1andboththemethodsMETH1,oneforclassandanotherforinterfaceiscalledusingtheobject.

Dump reportysubdel.

interfacei1.

data:numtypei.

methods:meth1.

endinterface.

classc1definition.

publicsection.

methods:meth1.classC1sownmethod

interfaces:i1.



endclass.


method:meth1.

write:/5Iammeth1inc1.

endmethod.

methodi1~meth1.

write:/5Iammeth1fromi1.

endmethod.

endclass.

startofselection.


createobjectoref.

write:/5oref>i1~num.

callmethodoref>meth1.

callmethodoref>i1~meth1.

Output 0

Iammeth1inc1

Iammeth1fromi1

5.2Interfacescanonlybeimplementedinthepublicsectionofaclass

Theme Thisprogramwillshowyouthatclassesimplementinganinterfacecanonlycontainthefeaturesoftheinterfaceinitspublicsection.



ProgramDescription

Inthisprogram,classC1istryingtoaccommodateinterfaceI1initsPRIVATESECTION.

Thiscreatesacompilationerror,establishingthetheme.

Dump reportysubdel.

interfacei1.

methods:meth1.

endinterface.

classc1definition.

protectedsection.

interfaces:i1.

endclass.

Output Compilationerrorwitherrormessage:

INTERFACESmayonlybeimplementedinthepublicsection.

5.3Aclasswithaninterfaceshouldimplementallthemethodsofthatinterface

Theme Thisprogramwillshowthataclasscontaininganinterfaceshouldimplementallthemethodsoftheinterfaceinitsimplementationsection.

ProgramDescrip

ClassC1implementsinterfaceI1,whichhasgottwomethods,METH1andMETH2.But,intheIMPLEMENTATIONsectionofclassC1,onlyMETH1isimplemented.

Thisprogramwillcreateacompilationerror,establishingthetheme.

Dump reportysubdel.

interfacei1.



methods:meth1,

meth2.

endinterface.

classc1definition.

publicsection.

interfaces:i1.

endclass.


methodi1~meth1.

write:/5Iammeth1fromi1.

endmethod.

endclass.

startofselection.


createobjectoref.

callmethodoref>i1~meth1.

Output Compilationerrorwitherrormessage:

ImplementationmissingformethodI1~METH2

5.4Valuesforinterfaceattributesareassignedatthetimeofinclusioninaclass

Theme Onecannotspecifyvaluesforattributeswhiledeclaringtheminaninterfacelikethefollowingfashion:DATA:TYPEVALUE



.

Insteadofdoingthat,onehastospecifythevaluesfordifferentattributesofinterfaceatthepointwheretheinterfaceisdeclaredinthepublicsectionofaclass.

ProgramDescr.

InterfaceI1containstwonumericattributes,NUM1andNUM2.

Inversion1oftheprogram,attemptismadetospecifythevalueswhiledefiningthoseattributesintheinterface.Thisversiondoesnotgetsuccessfullycompiledandthusestablishesthetheme.

Inversion2,valuesforinterfaceattributesarespecifiedatthetimewhenI1isincludedinthepublicsectionofclassC1.Thisversiongetssuccessfullycompiledandproducesaresult.

reportysubdel.

interfacei1.

data:num1typei,

num2typei.

endinterface.

classc1definition.

publicsection.

interfaces:i1DATAVALUESnum1=5num2=6.

methodsm1.

endclass.


methodm1.

write:/5i1~num1,

i1~num2.

endmethod.

endclass.



startofselection.


createobjectoref.

callmethodoref>m1.

reportysubdel.

interfacei1.

data:num1typeivalue5,

num2typeivalue6.

endinterface.

classc1definition.

publicsection.

interfaces:i1.

methodsm1.

endclass.


methodm1.

write:/5i1~num1,

i1~num2.

endmethod.

endclass.

startofselection.


createobjectoref.

callmethodoref>m1.



Version1Version2

Output Outputofversion1:

Compilationerrorwitherrormessage:Withinaninterface,youcannotuseVALUEwithattributes(exceptconstants)

Outputofversion2:

56

5.5UseofFINALmethodsfromInterface

Theme Thisprogramwilldemonstratehowtocreatefinalmethodinaclassfromoneofthemethodsofaninterface.

ProgramDescription

InterfaceI1containstwomethods:M1andM2.

I1isincludedandincorporatedinclass:C1withM2asafinalmethod.BoththemethodsareimplementedinclassC1.

ClassC2isasubclassofclassC1.Itredefinesmethod:I1~M1andreimplementsit,butitdoesnotdothatforI1~M2asthatisdeclaredasfinalmethod.

IntheSTARTOFSELECTIONblock,objectOREF1iscreatedfromclassC1andOREF2fromclassC2andboththemethodsM1andM2arecalledusingboththeobjects.

Dump reportysubdel.

interfacei1.

methods:m1,

m2.

endinterface.

classc1definition.



publicsection.

interfaces:I1finalmethodsm2.

endclass.


methodi1~m1.

write:/5Iamm1inc1.

endmethod.

methodi1~m2.

write:/5Iamm2inc1.

endmethod.

endclass.


publicsection.

methods:i1~m1redefinition.

endclass.


method:i1~m1.

write:/5Iamm1inc2.

endmethod.

endclass.

startofselection.

data:oref1typereftoc1,

oref2typereftoc2.

createobject:oref1,oref2.

callmethod:oref1>i1~m1,Output:Iamm1inc1



oref2>i1~m1,Output:Iamm1inc2

oref1>i1~m2,Output:Iamm2inc1

oref2>i1~m2.Output:Iamm2inc1

Output Iamm1inc1

Iamm1inc2

Iamm2inc1

Iamm2inc1

5.6UseofAbstractmethodsfromInterface

Theme Thisprogramwilldemonstratethewaybywhichamethodfromaninterfacecanbeusedasanabstractmethodforaclass.

Abstractmethodscanonlybeimplementedbythesubclasses.

Aclasscontaininganabstractmethodshouldbeabstractitself.

ProgramDesc.

vThisprogramcontainsaninterfaceI1withtwomethods,M1andM2.

vClassC1includesandimplementsmethodsofinterfaceI1,declaringmethodM2asanabstractmethod.Hence,classC1wasalsodeclaredasanabstractclass.

vClassC1implementsmethodI1~M1,butnotI1~M2asthisisanabstractmethod.

vClassC2isasubclassofC1,whichdefinesI1~M2.

vIntheSTARTOFSELECTIONblock,objectOREF2iscreatedfromclassC2(classC1cannotbeinstantiated,asthisisanabstractclass)andboththemethods:I1~M1andI1~M2arecalled.

Dump reportysubdel.

interfacei1.



methods:m1,

m2.

endinterface.

classc1definitionabstract.

publicsection.

interfaces:I1abstractmethodsm2.

endclass.


methodi1~m1.

write:/5Iamm1inc1.

endmethod.

endclass.


publicsection.

methods:i1~m2redefinition.

endclass.


method:i1~m2.

write:/5Iamm2inc2.

endmethod.

endclass.

startofselection.

data:oref2typereftoc2.

createobject:oref2.

callmethod:oref2>i1~m1,



oref2>i1~m2.

Output Iamm1inc1

Iamm2inc2

5.7UseofInterfaceReferenceVariable

Theme Thisprogramwillshowtheuseofinterfacereferencevariableandhowitcanbeusedtoaccessthecomponentsofaninterfaceinaclass(implementingthatinterface).Useofinterfacereferencevariablepavesthewayforpolymorphismviainterface.

ProgramDescrip.

InterfaceI1,included/implementedinclassC1hasthefollowingcomponents:

component nature

C_name Constantwithvalue=ABAP

inum Instanceattributewithvalue=5

cnum Staticattributeofvalue6

M1 Instancemethod

M2 StaticmethodClassC1implementsallthemethodsinitsIMPLEMENTATIONsection.

IntheSTARTOFSELECTIONblock,allthedifferentattributesandmethodsarecalledusingclassreferencevariableOREFfirst.

Then,interfacereferencevariableIREFisusedtodosimilarjobs,aftertheassignmentIREF=OREF.

Dump reportysubdel.

interfacei1.

constants:c_name(4)typecvalueABAP.

data:inumtypei.

classdata:cnumtypei.



methods:m1.

classmethods:m2.

endinterface.

classc1definition.

publicsection.

interfaces:I1datavaluesinum=5cnum=6.

endclass.


methodi1~m1.

write:/5Iamm1inc1.

endmethod.

methodi1~m2.

write:/5Iamclassmethodm2inc1.

endmethod.

endclass.

startofselection.

data:ireftypereftoi1,

oreftypereftoc1.

createobject:oref.

write:/5oref>i1~inum,

oref>i1~cnum,

c1=>i1~cnum.

callmethod:oref>i1~m1,

oref>i1~m2,

c1=>i1~m2.



write:/5syuline.

iref=oref.

write:/5iref>inum,

iref>cnum,

i1=>c_name.

callmethod:iref>m1,

iref>m2.

Output 566

Iamm1inc1

Iamclassmethodm2inc1


56ABAP

Iamm1inc1


5.8UseofNestedInterface

Theme Thisprogramwilldemonstratehowaninterfacecanbeincludedinanotherinterface.Andthefinalinterfacecontainingalltheinterfacescanbeusedinsideaclass.

ProgramDescr.

vInterfaceI1containsmethodM1.

vInterfaceI2includesinterfaceI1.However,italsocontainstwomethodsM1andM2ofitsown.

vClassC1containsinterfaceI2andimplementsmethods:I1~M1,I2~M1andI2~M2.



vObjectiscreatedfromclassC1andallthemethodsarecalled.

reportysubdel.

interfacei1.

methodsm1.

endinterface.

interfacei2.

methods:m1,m2.

interfacesi1.

endinterface.

classc1definition.

publicsection.

interfaces:i2.

endclass.


method:i1~m1.

write:/5Iamm1fromi1.

endmethod.

method:i2~m1.


endmethod.

method:i2~m2.


endmethod.

endclass.

STARTOFSELECTION.




createobjectoref.

callmethod:oref>i1~m1,Output:Iamm1fromi1

oref>i2~m1,Output:Iamm1fromi2

oref>i2~m2.Output:Iamm1fromi2

Output Iamm1fromi1

Iamm1fromi2

Iamm2fromi2

5.9UsingALIASES

Theme ThefullnameofacomponentwhichanInterfaceaddstoaclassoranotherinterfaceisintf~comp.Aliasnamescanbesubstitutedforthisnamewhen

definingcompoundinterfaces,or

declaringInterfacesinaclass

ProgramDescr.

InterfaceI1containsmethodM1.

InterfaceI2containsmethod:M1andM2and

Documents

ABAP OO Concept Topicwis Example _ Maagnusabap