上海德邦物流股份有限公司招聘java面试真题

上海德邦物流股份有限公司招聘java面试真题一、选择题(20)［含多选］。(请在正确的答案上打“J")Question1)Whichofthefollowingstatementsaretrue?Aninterface canonlycontainmethodand not variablesInterfacescannothaveconstructorsAclassmay extendonlyoneotherclass and implement onlyoneinterfaceInterfacesaretheJavaapproachtoaddressingitslackofmultipleinheritance,butrequireimplementingclassestocreatethefunctionalityoftheInterfaces.Question2)Which of thefollowingstatementsaretrue?The garbagecollectionalgorithminJava is vendorimplementedThe sizeofprimitivesisplatformdependentThe defaulttypeforanumericalliteral withdecimalcomponent is a float.You canmodifythevalueinanInstance of theIntegerclass with the setValuemethodQuestion3)Whichofthefollowingaretruestatements?I/O inJavacanonlybe performedusingthe Listener classesThe RandomAccessFileclass allowsyoutomove directly toany pointafile.ThecreationofanamedinstanceoftheFileclasscreatesamatchingfileintheunderlyingoperatingsystemonlywhentheclosemethodiscalled.ThecharacteristicsofaninstanceoftheFileclasssuchasthedirectoryseparator,dependonthecurrentunderlyingoperatingsystemQuestion4)WhatwillhappenwhenyouattempttocompileandrunthefollowingcodeclassBase{publicvoidBase(){System.out.println(“Base”)；}}publicclassInextendsBase{publicstaticvoidmain(Stringargv[]){Ini=newIn();})CompiletimeerrorBaseisakeywordCompilationandnooutputatruntimeOutputofBaseRuntimeerrorBasehasnovalidconstructorQuestion5)Youhaveapublicclasscalledmyclasswiththemainmethoddefinedasfollowspublicstaticvoidmain(Stringparm[]){System.out.println(parm[0]);}IfyouattempttocompiletheclassandruntheprogramasfollowsjavamyclasshelloWhatwillhappen?Compiletimeerror,mainisnotcorrectlydefinedRuntimeerror,mainisnotcorrectlydefinedCompilationandoutputofjavaCompilationandoutputofhelloQuestion6)WhichofthefollowingstatementsareNOTtrue?Ifaclasshasanyabstractmethodsitmustbedeclaredabstractitself.Whenappliedtoa class,thefinalmodifiermeans it cannotbe sub-classedAllmethodsinan abstractclassmustbedeclared as abstracttransientandvolatileareJavamodifiersQuestion7)Whatwillhappenwhenyouattempttocompileandrunthefollowingclass?classBase{Base(inti){System.out.println(“Base”)；))classSevernextendsBase{publicstaticvoidmain(Stringargv口){Severns=newSevern();)voidSevern(){System.out.println(“Severn”)；))Compilationandoutputofthestring“Severn”atruntimeCompilation and nooutput atruntimeCompiletimeerrorCompilation and outputof thestring “Base”Question8)Whichofthefollowingstatementsaretrue?Static methods cannot be overridentobenon staticStatic methods cannot be declaredasprivatePrivatemethodscannotbeoverloadedAnoverloadedmethodcannotthrowexceptionsnotcheckedinthebaseclassQuestion9)Whichofthefollowingstatementsaretrue?TheautomaticgarbagecollectionoftheJVMpreventsprogramsfromeverrunningoutofmemoryAprogramcansuggestthatgarbagecollectionbeperformedbutnotforceitGarbagecollectionisplatformindependentAnobjectbecomeseligibleforgarbagecollectionwhenallreferencesdenotingitaresettonull.Question10)GiventhefollowingcodepublicclassSytch{intx=2000;publicstaticvoidmain(Stringargv口){System.out.println(“Ms”+argv[1]+“Pleasepay$”+x);))WhatwillhappenifyouattempttocompileandrunthiscodewiththecommandlinejavaSytchJonesDiggleCompilation and output ofMs Diggle Please pay $2000CompiletimeerrorCompilation and output ofMs Jones Please pay $2000Compilation but runtime errorQuestion11)Youneedtoreadinthelinesofalargetextfilecontainingtensofmegabytesofdata.WhichofthefollowingwouldbemostsuitableforreadinginsuchafilenewFileInputStream(“”)newInputStreamReader(newFileInputStream(“”))newBufferedReader(newInputStreamReader(newFileInputStream(“”)))；newRandomAccessFileraf=newRandomAccessFile(“myfile.txt“，“+rw”)；Question12)Whichofthefollowingstatementsaretrue?Constructors cannothavea visibilitymodifierConstructorsarenotinheritedConstructors canonlyhave aprimitivereturntypeConstructors canbemarked publicandprotected,but notprivateQuestion13)Whichstatementistrue?1)An anonymous inner class may be declared as final.2)An anonymous inner class can be declared as private.3)An anonymous inner class can implementmultipleinterfaces.4)An anonymous inner class can accessfinalvariablesinany enclosingscope.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.From running to ready.From running to waiting.From waiting to running.From waiting to ready.Fromreadytowaiting.Question16)Whatistheresultofattemptingtocompileandrunthefollowingprogram?publicclassTest{privateinti=j;privateintj=10;publicstaticvoidmain(Stringargs[]){System.out.println((newTest()).i);))Compiler error complaining about accessrestriction ofprivatevariablesofTest.Compiler error complaining about forwardreferencing.No error - The output is 0;No error - The output is 10;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口) {CloseWindowCW=newCloseWindow();}}CompiletimeerrorRuntimeerrorCodecompilesbutFramesdoesnotlistentoWindowEventsCompileandrunssuccessfullyQuestion19)Whichstatementsdescribeguaranteedbehaviorofthegarbagecollectionandfinalizationmechanisms?Objectsare deletedwhentheycan no longerbe accessedthrough anyreference.The finalize() method will eventuallybecalledoneveryobject.The finalize() method will neverbecalled more thanonce onan object.An objectwill notbegarbagecollectedas long asitis possible foranactivepartof theprogramtoaccess it througha reference.The garbagecollector will useamarkand sweep algorithm.Question20)Aclassdesignrequiresthatamembervariableshouldbeaccessibleonlybysamepackage,whichmodiferwordshouldbeused?protectedpublicnomodiferprivate二.简答题。(80)(请