java选择题115.docx

java选择题115.docx

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java选择题115

单项选择115题

1.WhichistheJavakeywordusedtodenoteaclassmethod?

（a）class（b）static（c）private（d）final

2.Thetermclassvariableisasynonymfor

（a）aread-onlyvariable（b）aprivatedatafield

（c）astaticdatafield（d）aninstancevariable

3.WhichofthefollowingstatementsaboutclassvariablesinJavaisnottrue?

（a）Non-staticmethodsinaclasscanaccesstheclassvariabledefinedinthesameclass.

（b）Allobjectshavetheirowncopyoftheclassvariabledefinedintheinstantiatedclass.

（c）Classvariablesrequirethemodifierstaticinthedeclarations.

（d）Classvariablesdonotneedthereferencetotheobjectoftheinstantiatedclasstoaccessthem.

4.ConsiderthefollowingUMLclassdiagram.

Thediagramdescribesa

（a）one-to-onerelationship（b）relationshipbetweenasubclassandasuperclass

（c）self-containingclass（d）classwithoutmethods

5.Whenusingnoun-phraseanalysistomodelasoftwaresystem,whichofthefollowingshouldtypicallybeeliminatedfromthelistofpotentialclasses?

I.Referencestothesoftwaresystemitself

II.Nounsthatimplyrolesbetweenobjects

III.Synonymstoothernounsinthelist

（a）IandIIIonly（b）I,II,andIII（c）IIIonly（d）IIandIIIonly

6.WhichofthefollowingstatementsaboutconstructorsinJavaistrue?

（a）Aclassmustdefineatleastoneconstructor.

（b）Aclasscandefinemorethanoneconstructor.

（c）Aconstructormustbedefinedasstatic.

（d）Aconstructormustbedefinedaspublic.

7.Ifa（n）_____exceptioncanoccurinamethodthatdoesnothaveacatchblocktohandlethatexception,thenathrowsclausethatliststhisexceptionmustbepartofthemethod_____.

（a）unchecked,body（b）checked,body（c）checked,header（d）unchecked,header

8.Ifaclasscontainsaconstructor,thatconstructorwillbeinvoked

（a）onceatthebeginningofanyprogramthatusesthatclass

（b）eachtimeanobjectofthatclassisinstantiated

（c）oncethefirsttimeanobjectofthatclassisinstantiated

（d）eachtimeanobjectofthatclassgoesoutofscope

9.ConsiderthefollowingJavaprogramsegment.

importjava.io.*;

publicclassTest{

publicTest（）{

System.out.println（"default"）;

}

publicTest（inti）{

System.out.println（"non-default"）;

}

publicstaticvoidmain（String[]args）{

Testt=newTest

（2）;

}

}

Whichofthefollowingwillbeoutputduringexecutionoftheprogramsegment?

（a）Thelineoftext"default"

（b）Thelineoftext"default"followedbythelineoftext"non-default"

（c）Thelineoftext"non-default"followedbythelineoftext"default"

（d）Thelineoftext"non-default"

10.Fromwithinachildclass,itsparentclassisreferredtoviathekeyword

（a）super（b）this（c）parent（d）base

11.Whichofthefollowingstatementsimportstheentirepackagejava.utilintoaJavaprogram?

（a）importutil;（b）importutil.*;（c）importjava.util.*;（d）importjava.util;

12.ConsiderthefollowingJavaclassdefinitions.

publicclassObject1{

protectedStringd（）{

return"Hi";

}

}

publicclassObject2extendsObject1{

protectedStringd（）{

returnsuper.d（）;

}

}

Whichofthefollowingstatementsis（are）trueregardingthedefinitions?

I.ClassObject2inheritsfromclassObject1.

II.ClassObject2overridesmethodd.

III.Methoddreturnsequivalentresultswhenexecutedfromeitherclass.

（a）I,II,andIII（b）IandIIonly（c）IandIIIonly（d）IIIonly

13.Afterabreakpointishit,adebuggeristypicallyusedforwhichofthefollowingtasks?

I.Steppingthroughmethodcalls,linebylineII.Examiningastacktrace

III.Examiningvaluesofvariablesinthecurrentmethod

（a）IandIIIonly（b）IandIIonly（c）IIonly（d）I,II,andIII

14.WhichisaJavaaccessmodifierusedtodesignatethataparticulardatafieldwillnotbeinheritedbyasubclass?

（a）private（b）final（c）protected（d）default

15.Ifthemethodintsum（inta,intb）isdefinedinaJavaclassC,whichofthefollowingmethodscannotcoexistasadifferentmethodinclassC?

（a）intsum（intx,floaty）（b）intsum（floata,intb）

（c）floatsum（intx,floaty）（d）intsum（intx,inty）

16.ThenameofaJavasourcefile

（a）mustusetheextension.class

（b）mustbethesameastheclassitdefines,respectingcase

（c）hasnorestrictions

（d）mustbethesameastheclassitdefines,ignoringcase

17.WhichpackagedoesnotneedtobeexplicitlyimportedintoaJavaprogram?

（a）java.io（b）java.lang（c）java.applet（d）java.awt

18.Giventhefollowingcode,howmanytokenswillbeoutput?

StringTokenizerst=newStringTokenizer（"thisisatest"）;

while（st.hasMoreTokens（））{

stdOut.println（st.nextToken（））;

}

（a）1（b）0（c）4（d）3

19.ConsideranobjectstdIninstantiatedbytheJavastatementbelow.

privatestaticjava.io.BufferedReaderstdIn=

newjava.io.BufferedReader（

newjava.io.InputStreamReader（System.in））;

WhichofthefollowinglinesofcodecanbeusedtoreadanintegervaluefromstdIn?

（a）intvalue=stdIn.readInteger（）;（b）intvalue=Integer.parseInt（stdIn.readLine（））;

（c）intvalue=stdIn.readLine（）;（d）intvalue=Integer.parseInt（stdIn）;

20.WhatwillbeoutputwhenthefollowingJavaprogramsegmentisexecuted?

intx=5;

inty=2;

System.out.println（x+y）;

（a）7（b）52（c）52（d）5+2

21.Adifferencebetweenthemethodsprintandprintlnoftheclassjava.io.PrintWriteristhat

（a）printinsertsanewlineatthebeginningofitsoutput,butprintlndoesnot

（b）printlninsertsanewlineatthebeginningofitsoutput,butprintdoesnot

（c）printappendsanewlinetotheendofitsoutput,butprintlndoesnot

（d）printlnappendsanewlinetotheendofitsoutput,butprintdoesnot

22.InJava,exceptionsthatarenothandledarepassedupthe

（a）blockhierarchy（b）callstack（c）exceptionladder（d）catchblocks

23.AllJavaexceptionclassesarederivedfromtheclass

（a）java.lang.Error（b）java.lang.Throwable

（c）java.io.IOException（d）java.lang.RuntimeException

24.WhichofthefollowingistrueregardingJavaapplications?

（a）Theyareplatform-dependent.（b）Theyarecompiledintomachinecode.

（c）TheyareinterpretedbyaWebbrowser.（d）TheyarerunusingaJavainterpreter.

25.WhichmethodmustexistineveryJavaapplication?

（a）main（b）paint（c）begin（d）init

26.Whichofthefollowingstatementsis（are）trueabouttheuseofanasterisk（*）inaJavaimportstatement?

I.Itdoesnotincurrun-timeoverhead.

II.Itcanbeusedtoimportmultiplepackageswithasinglestatement.

III.Itcanbeusedtoimportmultipleclasseswithasinglestatement.

（a）I,II,andIII（b）IIIonly（c）Ionly（d）IandIIIonly

27.WhatwillbeoutputwhenthefollowingJavaprogramsegmentisexecuted?

intx=5;

inty=2;

System.out.println（x+y）;

（a）52（b）5+2（c）7（d）52

28.WhatisthenameoftheJDKprogramthatprocessesJavadoccomments?

（a）java（b）javac（c）javacom（d）javadoc

29.Atoolthatallowsprogrammerstoexecutelinesofaprogramonelineatatimeinordertohelplocatethesourceofaprogram'serrorsisknownasa（n）

（a）scope（b）exceptionhandler（c）debugger（d）stacktrace

30.UMLclassdiagramscandescribewhichofthefollowing?

I.Theinternalstructureofclasses

II.Relationshipsbetweenclasses

（a）Ionly（b）IandII（c）IIonly（d）None

31.Whenusingadebuggertostepthroughaprogram,ifthecurrentlinecontainsamethodcall,whichofthefollowingexecutesthecurrentlineandthenstopsexecutionbeforeexecutingthefirstlineinthecalledmethod?

（a）stepreturn（b）resume（c）stepinto（d）stepover

32.AccordingtoJavadocconvention,thefirstsentenceofeachJavadoccommentshouldbe

（a）asummarysentenceofthedeclaredentry（b）an@authortag

（c）theorderoflinesisnotimportant（d）an@versiontag

33.AccordingtotheJavacodeconventions,fileslongerthan_____linesshouldbe_____.

（a）100,encouraged（b）100,avoided（c）2000,encouraged（d）2000,avoided

34.AsanaidindebuggingaprograminJava,printstatementsmaybeusedtodisplaywhichofthefollowingtypesofinformation?

I.Thenamesofmethodsbeingcalled

II.Thevaluesoftheparametersofamethod

III.Thevaluesoftheinstancevariablesofaclass

（a）IIandIIIonly（b）IandIIIonly（c）IandIIonly（d）I,II,andIII

35.InaUMLdiagram,aspecialization/generalizationrelationshipischaracterizedbyalinebetweentwoclassesanda_____nexttothe_____class.

（a）triangle,generalization（b）triangle,specialization

（c）diamond,specialization（d）diamond,generalization

36.ConsiderthefollowingJavaprogramsegment.

PrintWriterfileOut=newPrintWriter（

newFileWriter（"output.txt"））;

Ifthefileoutput.txtalreadyexists,whichofthefollowingeventswilloccurwhentheprogramsegmentisexecuted?

（a）Theexistingcontentsofoutput.txtwillbepreserved.

（b）Theexistingcontentsofoutput.txtwillbeerased.

（c）AFileAlreadyExistsexceptionwillberaised.

（d）Arun-timeerrorwillbegenerated.

37.Ifaclasscontainsaconstructor,thatconstructorwillbeinvoked

（a）onceatthebeginningofanyprogramthatusesthatclass

（b）oncethefirsttimeanobjectofthatclassisinstantiated

（c）eachtimeanobjectofthatclassisinstantiated

（d）eachtimeanobjectofthatclassgoesoutofscope

38.Whenasubclassdefinesaninstancemethodwiththesamereturntypeandsignatureasamethodinitsparent,theparent'smethodissaidtobe

（a）overloaded