java开发工程师模拟试题2023

第页共页java开发工程师模拟试题2023java开发工程师模拟试题20231.Whichstatementaboutthegarbagecollectionmechanismaretrue?A.Garbagecollectionrequireadditionalprogramcodeincaseswheremultiplethreadsarerunning.B.Theprogrammercanindicatethatareferencethroughalocalvariableisnolongerofinterest.C.TheprogrammerhasamechanismthateXPlicitandimmediatelyfreesthememoryusedbyJavaobjects.D.ThegarbagecollectionmechanismcanfreethememoryusedbyJavaObjectatexpectabletime.E.ThegarbagecollectionsystemneverreclaimsmemoryfromobjectswhilearestillAccessibletorunninguserthreads.2.Givethefollowingmethod:1)publicvoidmethod(){2)Stringa,b;3)a=newString(“helloworld”);4)b=newString(“gameover”);5)System.out.println(a+b+”ok”);6)a=null;7)a=b;System.out.println(a);9)}Intheabsenceofpileroptimization,whichistheearliestpointtheobjectareferredisdefinitelyhandtobegarbagecollection.A.beforeline3B.beforeline5C.beforeline6D.beforeline7E.Beforeline93.Whichstatementaboutlisteneristrue?A.Mostponentallowmultiplelistenerstobeadded.B.Ifmultiplelistenerbeaddtoasingleponent,theeventonlyaffectedonelistener.C.ponentdon’tallowmultiplelistenerstobeadd.D.ThelistenermechanismallowsyoutocallanaddXXXListenermethodasmanytimesasisneeded,specifyingasmanydifferentlistenersasyourdesignrequire.4.Givethefollowingcode:publicclassExle{publicstaticvoidmain(Stringargs[]){intl=0;do{System.out.println(“Doingitforlis:”+l);}while(--l》0)System.out.println(“Finish”);}}Whichwellbeoutput:A.Doingitforlis3B.Doingitforlis1C.Doingitforlis2D.Doingitforlis0E.Doingitforlis–1F.Finish5.Givethecodefragment:1)switch(x){2)case1:System.out.println(“Test1”);break;3)case2:4)case3:System.out.println(“Test2”);break;6)}whichvalueofxwouldcause“Test2”totheoutput:A.1B.2C.3D.default6.Giveinpletedmethod:1)2){if(unsafe){//dosomething...}3)elseif(safe){//dotheother...}4)}ThemethodunsafewillthrowanIOException,whichpletesthemethodofdeclarationwhenaddedatlineone?A.publicIOExceptionmethodNameB.publicvoidmethodNameC.publicvoidmethodNamethrowIOExceptionD.publicvoidmethodNamethrowsIOExceptionE.publicvoidmethodNamethrowsException7.Givethecodefragment:if(x》4){System.out.println(“Test1”);}elseif(x》9){System.out.println(“Test2”);}else{System.out.println(“Test3”);}WhichrangeofvaluexwouldprodUCeofoutput“Test2”?A.x<4B.x》4C.x》9D.None8.Givethefollowingmethod:publicvoidexle{try{unsafe;System.out.println(“Test1”);}catch(SafeExceptione){System.out.println(“Test2”);}finally{System.out.println(“Test3”);}System.out.println(“Test4”);Whichwilldisplayifmethodunsaferunnormally?A.Test1B.Test2C.Test3D.Test49.Whichmethodyoudefineasthestartingpointofnewthreadinaclassfromwhichnewthethreadcanbeexecution?A.publicvoidstartB.publicvoidrunC.publicvoidintD.publicstaticvoidmain(Stringargs[])E.publicvoidrunnable10.Giventhefollowingclassdefinition:classA{protectedinti;A(inti){this.i=i;}}whichofthefollowingwouldbeavalidinnerclassforthisclass?Selectallvalidanswers:A.classB{}}B{System.out.println(“i=”+i);}}D.classB{classA{}}E.classA{}11.WhichmodifiershouldbeappliedtoamethodforthelockofobjectthistobeoBTainedpriortoexecutionanyofthemethodbody?A.synchronizedB.abstractC.finalD.staticE.public12.ThefollowingcodeisentirecontentsofafilecalledExle.java,causespreciselyoneerrorduringpilation:2)}3)classBaseClass{4)Stringstr;5)publicBaseClass{6)System.out.println(“ok”);}7)publicBaseClass(Strings){str=s;}9)}10)publicclassExle{11)publicvoidmethod{12)SubClasss=newSubClass(“hello”);13)BaseClassb=newBaseClass(“world”);14)}15)}Whichlinewouldbecausetheerror?A.9B.10C.11D.1213.Whichstatementiscorrectlydeclareavariableawhichissuitableforreferingtoanarrayof50stringemptyobject?A.String[]aB.Stringa[]C.chara[][]D.Stringa[50]F.Objecta[50]14.Givethefollowingjavasourcefragment://pointxpublicclassInteresting{//dosomething}WhichstatementiscorrectlyJavasyntaxatpointx?A.importjava.awt.*;B.packagemypackage;C.staticintPI=3.14D.publicclassMyClass{//dootherthing...}E.classMyClass{//dosomething...}15.Givethisclassoutline:classExle{privateintx;//restofclassbody...}AssumingthatxinvokedbythecodejavaExle,whichstatementcanmadexbedirectlyaccessibleinmainmethodofExle.java?A.changeprivateintxtopublicintxB.changeprivateintxtostaticintxC.changeprivateintxtoprotectedintxD.changeprivateintxtofinalintx16.Aclassdesignrequiresthatamembervariableshouldbeaccessibleonlybysamepackage,whichmodifierWordshouldbeused?A.protectedB.publicC.nomodifierD.private17.Whichmodifiershouldbeappliedtoadeclarationofaclassmembervariableforthevalueofvariabletoremainconstantafterthecreationoftheobject?18.Whichiscorrectedargumentofmainmethodofapplication?A.StringargsB.Stringar[]C.Chararg