SCJP認證試題及答案講課稿

1、Good is good, but better carries it.精益求精，善益求善。SCJP認證試題及答案-轉(zhuǎn)載對題目和答案謹做參考Q1Amethodis.1)animplementationofanabstraction.2)anattributedefiningthepropertyofaparticularabstraction.3)acategoryofobjects.4)anoperationdefiningthebehaviorforaparticularabstraction.5)ablueprintformakingoperations.Q2Anobjectis.1)w

2、hatclassesareinstantiatedfrom.2)aninstanceofaclass.3)ablueprintforcreatingconcreterealizationofabstractions.4)areferencetoanattribute.5)avariable.Q3Whichlinecontainsaconstructorinthisclassdefinition?publicclassCounter/(1)intcurrent,step;publicCounter(intstartValue,intstepValue)/(2)set(startValue);se

3、tStepValue(stepValue);publicintget()returncurrent;/(3)publicvoidset(intvalue)current=value;/(4)publicvoidsetStepValue(intstepValue)step=stepValue;/(5)1)Codemarkedwith(1)isaconstructor2)Codemarkedwith(2)isaconstructor3)Codemarkedwith(3)isaconstructor4)Codemarkedwith(4)isaconstructor5)Codemarkedwith(5

4、)isaConstructorQ4GiventhatThingisaclass,howmanyobjectsandreferencevariablesarecreatedbythefollowingcode?Thingitem,stuff;item=newThing();Thingentity=newThing();1)Oneobjectiscreated2)Twoobjectsarecreated3)Threeobjectsarecreated4)Onereferencevariableiscreated5)Tworeferencevariablesarecreated6)Threerefe

5、rencevariablesarecreated.Q5Aninstancemember1)isalsocalledastaticmember2)isalwaysavariable3)isneveramethod4)belongstoasingleinstance,nottotheclassasawhole5)alwaysrepresentsanoperationQ6HowdoobjectspassmessagesinJava?1)Theypassmessagesbymodifyingeachothersmembervariables2)Theypassmessagesbymodifyingth

6、estaticmembervariablesofeachothersclasses3)Theypassmessagesbycallingeachothersinstancemembermethods4)Theypassmessagesbycallingstaticmembermethodsofeachothersclasses.Q7Giventhefollowingcode,whichstatementsaretrue?classAintvalue1;classBextendsAintvalue2;1)ClassAextendsclassB.2)ClassBisthesuperclassofc

7、lassA.3)ClassAinheritsfromclassB.4)ClassBisasubclassofclassA.5)ObjectsofclassAhaveamembervariablenamedvalue2.Q8IfthissourcecodeiscontainedinafilecalledSmallProg.java,whatcommandshouldbeusedtocompileitusingtheJDK?publicclassSmallProgpublicstaticvoidmain(Stringargs)System.out.println(Goodluck!);1)java

8、SmallProg2)avacSmallProg3)javaSmallProg.java4)javacSmallProg.java5)javaSmallProgmainQ9Giventhefollowingclass,whichstatementscanbeinsertedatposition1withoutcausingthecodetofailcompilation?publicclassQ6db8inta;intb=0;staticintc;publicvoidm()intd;inte=0;/Position11)a+;2)b+;3)c+;4)d+;5)e+;Q10Whichstatem

9、entsaretrueconcerningtheeffectoftheandoperators?1)Fornon-negativevaluesoftheleftoperand,theandoperatorswillhavethesameeffect.2)Theresultof(-11)is0.3)Theresultof(-11)is-1.4)Thevaluereturnedbywillneverbenegativeaslongasthevalueoftherightoperandisequaltoorgreaterthan1.5)Whenusingtheoperator,theleftmost

10、bitofthebitrepresentationoftheresultingvaluewillalwaysbethesamebitvalueastheleftmostbitofthebitrepresentationoftheleftoperand.Q11Whatiswrongwiththefollowingcode?classMyExceptionextendsExceptionpublicclassQb4abpublicvoidfoo()trybar();finallybaz();catch(MyExceptione)publicvoidbar()throwsMyExceptionthr

11、ownewMyException();publicvoidbaz()throwsRuntimeExceptionthrownewRuntimeException();1)Sincethemethodfoo()doesnotcatchtheexceptiongeneratedbythemethodbaz(),itmustdeclaretheRuntimeExceptioninitsthrowsclause.2)Atryblockcannotbefollowedbybothacatchandafinallyblock.3)Anemptycatchblockisnotallowed.4)Acatch

12、blockcannotfollowafinallyblock.5)Afinallyblockmustalwaysfollowoneormorecatchblocks.Q12Whatwillbewrittentothestandardoutputwhenthefollowingprogramisrun?publicclassQd803publicstaticvoidmain(Stringargs)Stringword=restructure;System.out.println(word.substring(2,3);1)est2)es3)str4)st5)sQ13Giventhatastati

13、cmethoddoIt()inaclassWorkrepresentsworktobedone,whatblockofcodewillsucceedinstartinganewthreadthatwilldothework?CODEBLOCKA:Runnabler=newRunnable()publicvoidrun()Work.doIt();Threadt=newThread(r);t.start();CODEBLOCKB:Threadt=newThread()publicvoidstart()Work.doIt();t.start();CODEBLOCKC:Runnabler=newRun

14、nable()publicvoidrun()Work.doIt();r.start();CODEBLOCKD:Threadt=newThread(newWork();t.start();CODEBLOCKE:Runnablet=newRunnable()publicvoidrun()Work.doIt();t.run();1)CodeblockA.2)CodeblockB.3)CodeblockC.4)CodeblockD.5)CodeblockE.Q14WritealineofcodethatdeclaresavariablenamedlayoutoftypeLayoutManagerand

15、initializesitwithanewobject,whichwhenusedwithacontainercanlayoutcomponentsinarectangulargridofequal-sizedrectangles,3componentswideand2componentshigh.Q15publicclassQ275dstaticinta;intb;publicQ275d()intc;c=a;a+;b+=c;publicstaticvoidmain(Stringargs)newQ275d();1)Thecodewillfailtocompile,sincetheconstru

16、ctoristryingtoaccessstaticmembers.2)Thecodewillfailtocompile,sincetheconstructoristryingtousestaticmembervariableabeforeithasbeeninitialized.3)Thecodewillfailtocompile,sincetheconstructoristryingtousemembervariablebbeforeithasbeeninitialized.4)Thecodewillfailtocompile,sincetheconstructoristryingtous

17、elocalvariablecbeforeithasbeeninitialized.5)Thecodewillcompileandrunwithoutanyproblems.Q16Whatwillbewrittentothestandardoutputwhenthefollowingprogramisrun?publicclassQ63e3publicstaticvoidmain(Stringargs)System.out.println(92);1)812)73)114)05)falseQ17Whichstatementsaretrueconcerningthedefaultlayoutma

18、nagerforcontainersinthejava.awtpackage?1)ObjectsinstantiatedfromPaneldonothaveadefaultlayoutmanager.2)ObjectsinstantiatedfromPanelhaveFlowLayoutasdefaultlayoutmanager.3)ObjectsinstantiatedfromApplethaveBorderLayoutasdefaultlayoutmanager.4)ObjectsinstantiatedfromDialoghaveBorderLayoutasdefaultlayoutm

19、anager.5)ObjectsinstantiatedfromWindowhavethesamedefaultlayoutmanagerasinstancesofApplet.Q18Whichdeclarationswillallowaclasstobestartedasastandaloneprogram?1)publicvoidmain(Stringargs)2)publicvoidstaticmain(Stringargs)3)publicstaticmain(Stringargv)4)finalpublicstaticvoidmain(Stringarray)5)publicstat

20、icvoidmain(Stringargs)Q19Underwhichcircumstanceswillathreadstop?1)ThemethodwaitforId()inclassMediaTrackeriscalled.2)Therun()methodthatthethreadisexecutingends.3)Thecalltothestart()methodoftheThreadobjectreturns.4)Thesuspend()methodiscalledontheThreadobject.5)Thewait()methodiscalledontheThreadobject.

21、Q20Whencreatingaclassthatassociatesasetofkeyswithasetofvalues,whichoftheseinterfacesismostapplicable?1)Collection2)Set3)SortedSet4)MapQ21WhatdoesthevaluereturnedbythemethodgetID()foundinclassjava.awt.AWTEventuniquelyidentify?1)Theparticulareventinstance.2)Thesourceoftheevent.3)Thesetofeventsthatwere

22、triggeredbythesameaction.4)Thetypeofevent.5)Thetypeofcomponentfromwhichtheeventoriginated.Q22Whatwillbewrittentothestandardoutputwhenthefollowingprogramisrun?classBaseinti;Base()add(1);voidadd(intv)i+=v;voidprint()System.out.println(i);classExtensionextendsBaseExtension()add(2);voidadd(intv)i+=v*2;p

23、ublicclassQd073publicstaticvoidmain(Stringargs)bogo(newExtension();staticvoidbogo(Baseb)b.add(8);b.print();1)92)183)204)215)22Q23Whichlinesofcodearevaliddeclarationsofanativemethodwhenoccurringwithinthedeclarationofthefollowingclass?publicclassQf575/insertdeclarationofanativemethodhere1)nativepublic

24、voidsetTemperature(intkelvin);2)privatenativevoidsetTemperature(intkelvin);3)protectedintnativegetTemperature();4)publicabstractnativevoidsetTemperature(intkelvin);5)nativeintsetTemperature(intkelvin)Q24HowdoestheweightypropertyoftheGridBagConstraintsobjectsusedingridbaglayoutaffectthelayoutofthecom

25、ponents?1)Itaffectswhichgridcellthecomponentsendupin.2)Itaffectshowtheextraverticalspaceisdistributed.3)Itaffectsthealignmentofeachcomponent.4)Itaffectswhetherthecomponentscompletelyfilltheirallotteddisplayareavertically.Q25Whichstatementscanbeinsertedattheindicatedpositioninthefollowingcodetomaketh

26、eprogramwrite1onthestandardoutputwhenrun?publicclassQ4a39inta=1;intb=1;intc=1;classInnerinta=2;intget()intc=3;/insertstatementherereturnc;Q4a39()Inneri=newInner();System.out.println(i.get();publicstaticvoidmain(Stringargs)newQ4a39();1)c=b;2)c=this.a;3)c=this.b;4)c=Q4a39.this.a;5)c=c;Q26Whichistheear

27、liestlineinthefollowingcodeafterwhichtheobjectcreatedonthelinemarked(0)willbeacandidateforbeinggarbagecollected,assumingnocompileroptimizationsaredone?publicclassQ76a9staticStringf()Stringa=hello;Stringb=bye;/(0)Stringc=b+!;/(1)Stringd=b;b=a;/(2)d=a;/(3)returnc;/(4)publicstaticvoidmain(Stringargs)St

28、ringmsg=f();System.out.println(msg);/(5)1)Thelinemarked(1).2)Thelinemarked(2).3)Thelinemarked(3).4)Thelinemarked(4).5)Thelinemarked(5).Q27WhichmethodsfromtheStringandStringBufferclassesmodifytheobjectonwhichtheyarecalled?1)ThecharAt()methodoftheStringclass.2)ThetoUpperCase()methodoftheStringclass.3)

29、Thereplace()methodoftheStringclass.4)Thereverse()methodoftheStringBufferclass.5)Thelength()methodoftheStringBufferclass.Q28Whichstatements,wheninsertedattheindicatedpositioninthefollowingcode,willcausearuntimeexceptionwhenattemptingtoruntheprogram?classAclassBextendsAclassCextendsApublicclassQ3ae4pu

30、blicstaticvoidmain(Stringargs)Ax=newA();By=newB();Cz=newC();/insertstatementhere1)x=y;2)z=x;3)y=(B)x;4)z=(C)y;5)y=(A)y;Q29WhichofthesearekeywordsinJava?1)default2)NULL3)String4)throws5)longQ30Itisdesirablethatacertainmethodwithinacertainclasscanonlybeaccessedbyclassesthataredefinedwithinthesamepacka

31、geastheclassofthemethod.Howcansuchrestrictionsbeenforced?1)Markthemethodwiththekeywordpublic.2)Markthemethodwiththekeywordprotected.3)Markthemethodwiththekeywordprivate.4)Markthemethodwiththekeywordpackage.5)Donotmarkthemethodwithanyaccessibilitymodifiers.Q31Whichcodefragmentswillsucceedininitializi

32、ngatwo-dimensionalarraynamedtabwithasizethatwillcausetheexpressiontab32toaccessavalidelement?CODEFRAGMENTA:inttab=0,0,0,0,0,0;CODEFRAGMENTB:inttab=newint4;for(inti=0;iCODEFRAGMENTC:inttab=0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0;CODEFRAGMENTD:inttab32;CODEFRAGMENTE:inttab=0,0,0,0,0,0,0,0,0,0,0,0;1)Codefragme

33、ntA.2)CodefragmentB.3)CodefragmentC.4)CodefragmentD.5)CodefragmentE.Q32Whatwillbetheresultofattemptingtorunthefollowingprogram?publicclassQaa75publicstaticvoidmain(Stringargs)Stringarr=,null,1,2,1,null,3,1,null;System.out.println(arr.length+arr12.length);1)TheprogramwillterminatewithanArrayIndexOutO

34、fBoundsException.2)TheprogramwillterminatewithaNullPointerException.3)4willbewrittentostandardoutput.4)6willbewrittentostandardoutput.5)7willbewrittentostandardoutput.Q33Whichexpressionswillevaluatetotrueifprecededbythefollowingcode?Stringa=hello;Stringb=newString(a);Stringc=a;chard=h,e,l,l,o;1)(a=H

35、ello)2)(a=b)3)(a=c)4)a.equals(b)5)a.equals(d)Q34Whichstatementsconcerningthefollowingcodearetrue?classApublicA()publicA(inti)this();classBextendsApublicbooleanB(Stringmsg)returnfalse;classCextendsBprivateC()super();publicC(Stringmsg)this();publicC(inti)1)Thecodewillfailtocompile.2)TheconstructorinAt

36、hattakesanintasanargumentwillneverbecalledasaresultofconstructinganobjectofclassBorC.3)ClassChasthreeconstructors.4)ObjectsofclassBcannotbeconstructed.5)AtmostoneoftheconstructorsofeachclassiscalledasaresultofconstructinganobjectofclassC.Q35Giventwocollectionobjectsreferencedbycol1andcol2,whichofthe

37、sestatementsaretrue?1)Theoperationcol1.retainAll(col2)willnotmodifythecol1object.2)Theoperationcol1.removeAll(col2)willnotmodifythecol2object.3)Theoperationcol1.addAll(col2)willreturnanewcollectionobject,containingelementsfrombothcol1andcol2.4)Theoperationcol1.containsAll(Col2)willnotmodifythecol1ob

38、ject.Q36Whichstatementsconcerningtherelationshipsbetweenthefollowingclassesaretrue?classFoointnum;Bazcomp=newBaz();classBarbooleanflag;classBazextendsFooBarthing=newBar();doublelimit;1)ABarisaBaz.2)AFoohasaBar.3)ABazisaFoo.4)AFooisaBaz.5)ABazhasaBar.Q37Whichstatementsconcerningthevalueofamembervaria

39、blearetrue,whennoexplicitassignmentshavebeenmade?1)Thevalueofanintisundetermined.2)Thevalueofallnumerictypesiszero.3)Thecompilermayissueanerrorifthevariableisusedbeforeitisinitialized.4)ThevalueofaStringvariableis(emptystring).5)Thevalueofallobjectvariablesisnull.Q38Whichstatementsdescribeguaranteed

40、behaviorofthegarbagecollectionandfinalizationmechanisms?1)Objectsaredeletedwhentheycannolongerbeaccessedthroughanyreference.2)Thefinalize()methodwilleventuallybecalledoneveryobject.3)Thefinalize()methodwillneverbecalledmorethanonceonanobject.4)Anobjectwillnotbegarbagecollectedaslongasitispossiblefor

41、anactivepartoftheprogramtoaccessitthroughareference.5)Thegarbagecollectorwilluseamarkandsweepalgorithm.Q39Whichcodefragmentswillsucceedinprintingthelastargumentgivenonthecommandlinetothestandardoutput,andexitgracefullywithnooutputifnoargumentsaregiven?CODEFRAGMENTA:publicstaticvoidmain(Stringargs)if

42、(args.length!=0)System.out.println(argsargs.length-1);CODEFRAGMENTB:publicstaticvoidmain(Stringargs)trySystem.out.println(argsargs.length);catch(ArrayIndexOutOfBoundsExceptione)CODEFRAGMENTC:publicstaticvoidmain(Stringargs)intix=args.length;Stringlast=argsix;if(ix!=0)System.out.println(last);CODEFRA

43、GMENTD:publicstaticvoidmain(Stringargs)intix=args.length-1;if(ix0)System.out.println(argsix);CODEFRAGMENTE:publicstaticvoidmain(Stringargs)trySystem.out.println(argsargs.length-1);catch(NullPointerExceptione)1)CodefragmentA.2)CodefragmentB.3)CodefragmentC.4)CodefragmentD.5)CodefragmentE.Q40Whichofth

44、esestatementsconcerningthecollectioninterfacesaretrue?1)SetextendsCollection.2)AllmethodsdefinedinSetarealsodefinedinCollection.3)ListextendsCollection.4)AllmethodsdefinedinListarealsodefinedinCollection.5)MapextendsCollection.Q41Whatisthenameofthemethodthatthreadscanusetopausetheirexecutionuntilsig

45、nalledtocontinuebyanotherthread?Fillinthenameofthemethod(donotincludeaparameterlist).Q42Giventhefollowingclassdefinitions,whichexpressionidentifieswhethertheobjectreferredtobyobjwascreatedbyinstantiatingclassBratherthanclassesA,CandD?classAclassBextendsAclassCextendsBclassDextendsA1)objinstanceofB2)

46、objinstanceofA&!(objinstanceofC)3)objinstanceofB&!(objinstanceofC)4)objinstanceofC|objinstanceofD5)(objinstanceofA)&!(objinstanceofC)&!(objinstanceofD)Q43Whatwillbewrittentothestandardoutputwhenthefollowingprogramisrun?publicclassQ8499publicstaticvoidmain(Stringargs)doubled=-2.9;inti=(int)d;i*=(int)

47、Math.ceil(d);i*=(int)Math.abs(d);System.out.println(i);1)122)183)84)125)27Q44Whatwillbewrittentothestandardoutputwhenthefollowingprogramisrun?publicclassQcb90inta;intb;publicvoidf()a=0;b=0;intc=0;g(b,c);System.out.println(a+b+c0+);publicvoidg(intb,intc)a=1;b=1;c0=1;publicstaticvoidmain(Stringargs)Qc

48、b90obj=newQcb90();obj.f();1)0002)0013)0104)1005)101Q45Whichstatementsconcerningtheeffectofthestatementgfx.drawRect(5,5,10,10)aretrue,giventhatgfxisareferencetoavalidGraphicsobject?1)Therectangledrawnwillhaveatotalwidthof5pixels.2)Therectangledrawnwillhaveatotalheightof6pixels.3)Therectangledrawnwill

49、haveatotalwidthof10pixels.4)Therectangledrawnwillhaveatotalheightof11pixels.Q46Giventhefollowingcode,whichcodefragments,wheninsertedattheindicatedlocation,willsucceedinmakingtheprogramdisplayabuttonspanningthewholewindowarea?importjava.awt.*;publicclassQ1e65publicstaticvoidmain(Stringargs)Windowwin=

50、newFrame();Buttonbut=newButton(button);/insertcodefragmentherewin.setSize(200,200);win.setVisible(true);1)win.setLayout(newBorderLayout();win.add(but);2)win.setLayout(newGridLayout(1,1);win.add(but);3)win.setLayout(newBorderLayout();win.add(but,BorderLayout.CENTER);4)win.add(but);5)win.setLayout(new

51、FlowLayout();win.add(but);Q47Whichmethodimplementationswillwritethegivenstringtoafilenamedfile,usingUTF8encoding?IMPLEMENTATIONA:publicvoidwrite(Stringmsg)throwsIOExceptionFileWriterfw=newFileWriter(newFile(file);fw.write(msg);fw.close();IMPLEMENTATIONB:publicvoidwrite(Stringmsg)throwsIOExceptionOut

52、putStreamWriterosw=newOutputStreamWriter(newFileOutputStream(file),UTF8);osw.write(msg);osw.close();IMPLEMENTATIONC:publicvoidwrite(Stringmsg)throwsIOExceptionFileWriterfw=newFileWriter(newFile(file);fw.setEncoding(UTF8);fw.write(msg);fw.close();IMPLEMENTATIOND:publicvoidwrite(Stringmsg)throwsIOExce

53、ptionFilterWriterfw=FilterWriter(newFileWriter(file),UTF8);fw.write(msg);fw.close();IMPLEMENTATIONE:publicvoidwrite(Stringmsg)throwsIOExceptionOutputStreamWriterosw=newOutputStreamWriter(newOutputStream(newFile(file),UTF8);osw.write(msg);osw.close();1)ImplementationA.2)ImplementationB.3)Implementati

54、onC.4)ImplementationD.5)ImplementationE.Q48Whicharevalididentifiers?1)_class2)$value$3)zer4)ngstr5)2muchuqQ49Whatwillbetheresultofattemptingtocompileandrunthefollowingprogram?publicclassQ28fdpublicstaticvoidmain(Stringargs)intcounter=0;l1:for(inti=10;i0;i-)l2:intj=0;while(ji)breakl2;if(i=j)counter+;

55、continuel1;counter-;System.out.println(counter);1)Theprogramwillfailtocompile.2)Theprogramwillnotterminatenormally.3)Theprogramwillwrite10tothestandardoutput.4)Theprogramwillwrite0tothestandardoutput.5)Theprogramwillwrite9tothestandardoutput.Q50Giventhefollowinginterfacedefinition,whichdefinitionsar

56、evalid?interfaceIvoidsetValue(intval);intgetValue();DEFINITIONA:(a)classAextendsIintvalue;voidsetValue(intval)value=val;intgetValue()returnvalue;DEFINITIONB:(b)interfaceBextendsIvoidincrement();DEFINITIONC:(c)abstractclassCimplementsIintgetValue()return0;abstractvoidincrement();DEFINITIOND:(d)interf

57、aceDimplementsIvoidincrement();DEFINITIONE:(e)classEimplementsIintvalue;publicvoidsetValue(intval)value=val;1)DefinitionA.2)DefinitionB.3)DefinitionC.4)DefinitionD.5)DefinitionE.Q51Whichstatementsconcerningthemethodsnotify()andnotifyAll()aretrue?1)InstancesofclassThreadhaveamethodcallednotify().2)Ac

58、alltothemethodnotify()willwakethethreadthatcurrentlyownsthemonitoroftheobject.3)Themethodnotify()issynchronized.4)ThemethodnotifyAll()isdefinedinclassThread.5)Whenthereismorethanonethreadwaitingtoobtainthemonitorofanobject,thereisnowaytobesurewhichthreadwillbenotifiedbythenotify()method.Q52Whichstat

59、ementsconcerningthecorrelationbetweentheinnerandouterinstancesofnon-staticinnerclassesaretrue?1)Membervariablesoftheouterinstancearealwaysaccessibletoinnerinstances,regardlessoftheiraccessibilitymodifiers.2)Membervariablesoftheouterinstancecanneverbereferredtousingonlythevariablenamewithintheinnerin

60、stance.3)Morethanoneinnerinstancecanbeassociatedwiththesameouterinstance.4)Allvariablesfromtheouterinstancethatshouldbeaccessibleintheinnerinstancemustbedeclaredfinal.5)Aclassthatisdeclaredfinalcannothaveanyinnerclasses.Q53Whatwillbetheresultofattemptingtocompileandrunthefollowingcode?publicclassQ6b