上海德邦物流股份有限公司招聘java面試真題

上海德邦物流股份有限公司招聘java面試真題一、選擇題(20)［含多選］。(請在正確的答案上打"J")Question1)Whichofthefollowingstatementsaretrue?AninterfacecanonlycontainmethodandnotvariablesInterfacescannothaveconstructorsAclassmayextendonlyoneotherclassandimplementonlyoneinterfaceInterfacesaretheJavaapproachtoaddressingitslackofmultipleinheritance,butrequireimplementingclassestocreatethefunctionalityoftheInterfaces.Question2)Whichofthefollowingstatementsaretrue?ThegarbagecollectionalgorithminJavaisvendorimplementedThesizeofprimitivesisplatformdependentThedefaulttypeforanumericalliteralwithdecimalcomponentisafloat.YoucanmodifythevalueinanInstanceoftheIntegerclasswiththesetValuemethodQuestion3)Whichofthefollowingaretruestatements?I/OinJavacanonlybeperformedusingtheListenerclassesTheRandomAccessFileclassallowsyoutomovedirectlytoanypointafile.ThecreationofanamedinstanceoftheFileclasscreatesamatchingfileintheunderlyingoperatingsystemonlywhentheclosemethodiscalled.3)3)CompilationandoutputofjavaThecharacteristicsofaninstanceoftheFileclasssuchasthedirectoryseparator,dependonthecurrentunderlyingoperatingsystemQuestion4)WhatwillhappenwhenyouattempttocompileandrunthefollowingcodeclassBase{publicvoidBase(){System.out.println(“Base”);}}publicclassInextendsBase{publicstaticvoidmain(Stringargv[]){Ini=newIn();}}CompiletimeerrorBaseisakeywordCompilationandnooutputatruntimeOutputofBaseRuntimeerrorBasehasnovalidconstructorQuestion5)Youhaveapublicclasscalledmyclasswiththemainmethoddefinedasfollowspublicstaticvoidmain(Stringparm[]){System.out.println(parm[0]);}IfyouattempttocompiletheclassandruntheprogramasfollowsjavamyclasshelloWhatwillhappen?Compiletimeerror,mainisnotcorrectlydefinedRuntimeerror,mainisnotcorrectlydefinedCompilationandoutputofhelloQuestion6)WhichofthefollowingstatementsareNOTtrue?Ifaclasshasanyabstractmethodsitmustbedeclaredabstractitself.Whenappliedtoaclass,thefinalmodifiermeansitcannotbesub-classedAllmethodsinanabstractclassmustbedeclaredasabstracttransientandvolatileareJavamodifiersQuestion7)Whatwillhappenwhenyouattempttocompileandrunthefollowingclass?classBase{Base(inti){System.out.println(“Base”);}}classSevernextendsBase{publicstaticvoidmain(Stringargv[]){Severns=newSevern();}voidSevern(){System.out.println(“Severn”);}}Compilationandoutputofthestring”Severn”atruntimeCompilationandnooutputatruntimeCompiletimeerrorCompilationandoutputofthestring”Base”Question8)Whichofthefollowingstatementsaretrue?StaticmethodscannotbeoverridentobenonstaticStaticmethodscannotbedeclaredasprivatePrivatemethodscannotbeoverloadedAnoverloadedmethodcannotthrowexceptionsnotcheckedinthebaseclassQuestion9)Whichofthefollowingstatementsaretrue?TheautomaticgarbagecollectionoftheJVMpreventsprogramsfromeverrunningoutofmemoryAprogramcansuggestthatgarbagecollectionbeperformedbutnotforceitGarbagecollectionisplatformindependentAnobjectbecomeseligibleforgarbagecollectionwhenallreferencesdenotingitaresettonull.Question10)GiventhefollowingcodepublicclassSytch{intx=2000;publicstaticvoidmain(Stringargv[]){System.out.println(“Ms”+argv[1]+”Pleasepay$”+x);}WhatwillhappenifyouattempttocompileandrunthiscodewiththecommandlinejavaSytchJonesDiggleCompilationandoutputofMsDigglePleasepay$2000CompiletimeerrorCompilationandoutputofMsJonesPleasepay$2000CompilationbutruntimeerrorQuestion11)Youneedtoreadinthelinesofalargetextfilecontainingtensofmegabytesofdata.WhichofthefollowingwouldbemostsuitableforreadinginsuchafilenewFileInputStream(“”)newInputStreamReader(newFileInputStream(“”))newBufferedReader(newInputStreamReader(newFileInputStream(“”)));newRandomAccessFileraf=newRandomAccessFile(“myfile.txt”,”+rw”);Question12)Whichofthefollowingstatementsaretrue?ConstructorscannothaveavisibilitymodifierConstructorsarenotinheritedConstructorscanonlyhaveaprimitivereturntypeConstructorscanbemarkedpublicandprotected,butnotprivateQuestion13)Whichstatementistrue?1)Ananonymousinnerclassmaybedeclaredasfinal.2)Ananonymousinnerclasscanbedeclaredasprivate.3)Ananonymousinnerclasscanimplementmultipleinterfaces.4)Ananonymousinnerclasscanaccessfinalvariablesinanyenclosingscope.5)Constructionofaninstanceofastaticinnerclassrequiresaninstanceofheenclosingouterclass.Question14)publicclassFoo{publicstaticvoidmain(Stringsgf[]){StringBuffera=newStringBuffer(“A”);StringBufferb=newStringBuffer(“B”);operate(a,b);System.out.println(a+”,”+b);}staticvoidoperate(StringBufferx,StringBuffery){x.append(y);y=x;}}Whatistheresult?1)Thecodecompilesandprints“A.B”.2)Thecodecompilesandprints“A.A”.3)Thecodecompilesandprints“B.B”.4)Thecodecompilesandprints“AB.B”.5)Thecodecompilesandprints“AB.AB”.Question15)Whichofthefollowingthreadstatetransitionsarevalid?Fromreadytorunning.Fromrunningtoready.Fromrunningtowaiting.Fromwaitingtorunning.Fromwaitingtoready.Fromreadytowaiting.Question16)Whatistheresultofattemptingtocompileandrunthefollowingprogram?publicclassTest{privateinti=j;privateintj=10;publicstaticvoidmain(Stringargs[]){System.out.println((newTest()).i);}}CompilererrorcomplainingaboutaccessrestrictionofprivatevariablesofTest.Compilererrorcomplainingaboutforwardreferencing.Noerror-Theoutputis0;Noerror-Theoutputis10;Question17)Whichtwocannotdirectlycauseathreadtostopexecuting?1)exitingfromasynchronizedblock2)callingthewaitmethodonanobject3)callingthenotifymethodonanobject4)callingareadmethodonanInputStreamobject5)callingthesetPrioritymethodonathreadobjectQuestion18)Whichofthefollowingarecorrect,ifyoucompilethefollowingcode?publicclassCloseWindowextendsFrameimplementsWindowListener{publicCloseWindow(){addWindowListener(this);//ThisislistenerregistrationsetSize(300,300);setVisible(true);}publicvoidwindowClosing(WindowEvente){System.exit(0);}publicstaticvoidmain(Stringargs[]){CloseWindowCW=newCloseWindow();}}CompiletimeerrorRuntimeerrorCodecompilesbutFramesdoesnotlistentoWindowEventsCompileandrunssuccessfullyQuestion19)Whichstatementsdescribeguaranteedbehaviorofthegarbagecollectionandfinalizationmechanisms?Objectsaredeletedwhentheycannolongerbeaccessedthroughanyreference.Thefinalize()methodwilleventuallybecalledoneveryobject.Thefinalize()methodwillneverbecalledmorethanonceonanobject.Anobjectwillnotbegarbagecollectedaslongasitispossibleforanactivepartoftheprogramtoaccessitthroughareference.Thegarbagecollectorwilluseamarkandsweepalgorithm.Question20)Aclassdesignrequiresthatamembervariableshouldbeaccessibleonlybysamepackage,whichmodiferwordshouldbeused?protectedpublicnomodiferprivate二．簡答題。(80)(請注意字跡填寫工整)說明SQL語言中的Select中的Having子句作用。(5)解釋UnionAll與Union的區(qū)別。(5)現(xiàn)