重载和覆盖.docx
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重载和覆盖
1.Methodsandvariblesthatdothebackgroundworkofaclassareknownasimplementationdetails.Theimplementation
detailsencapsulatedclassshouldbegivenwhichaccess?
c
A.Public
B.Thedefault
C.Private/*˽ÓеÄÄÜʵÏÖϸ½Ú*/
D.Protected
E.Itdoesnotmatter
2.Whichofthefollowingisnotabenefitofencapsulation?
A.Clarityofcode
B.Codeefficiency
C.Theabilitytoaddfuntionalitylateron
D.Modificationrequireslesscodingchanges
3.Given:
1.publicclassRectangle{
2.}
3.
4.publicclassSquareextendsRectangle{
5.}
WhatistherelationshipbetweenRectangleandSquare?
b/*¾ØÐÎÊÇÒ»¸öÕý·½ÐÎ*/
A.hasa
B.isa
C.It'sbothanisaandhasarelationship.
D.Therelationshipisneitheranisaorahasarelationship.
4.Given:
1.publicclassVehicle{
2.privateEnginetheEngine;
3.}
4.
5.publicclassEngine{
6.}
WhatistherelationshipbetweenVehicleandEngine?
a/*¿¨³µÓÐÒ»¸ö·¢¶¯»ú*/
A.hasa
B.isa
C.It'sbothanisaandhasarelationship.
D.Therelationshipisneitheranisaorahasarelationship.
5.Given:
1.publicinterfaceMoveable{
2.publicvoidmoveObject（）;
3.}
4.
5.publicclassBitmapimplementsMoveable{
6.publicvoidmoveObject（）{
7.//bodyomitted
8.}
9.}
WhatistherelationshipbetweenMovableandBitmap?
b
A.hasa
B.isa
C.It'sbothanisaandhasarelationship.
D.Therelationshipisneitheranisanorahasarelationship.
6.Given:
1.classSuperTest{
2.publicdoublegetNumber（）{
3.returnMath.random（）*100;
4.}
5.}
6.
7.classTestextendsSuperTest{
8.publicintgetNumber（）{
9.return（int）（Math.random（）*100）;
10.}
11.publicstaticvoidmain（String[]args）{
12.Testt=newTest（）;
13.System.out.println（t.getNumber（））;
14.}
15.}
Whichoftheseresultscouldoccurfromthiscode?
（Chooseallthatapply）f/*×ÓÀà·½·¨µÄ·µ»ØÀàÐÍСÓÚ¸¸Àà*/
A.59
B.34.234
C.134.234
D.134
E.100
F.Thiscodewillnotcompile.
7.Given:
1.classSuperTest{
2.publicdoublegetNumber（）{
3.returnMath.random（）*100;
4.}
5.}
6.
7.classTestextendsSuperTest{
8.publicintgetNumber（intmax）{
9.return（int）（Math.random（）*max）;
10.}
11.
12.publicIntegergetNumber（intmax）{
13.inttemp=（int）（Math.random（）*max）;
14.returnnewInteger（temp）;
15.}
16.
17.publicstaticvoidmain（String[]args）{
18.Testt=newTest（）;
19.System.out.println（t.getNumber（））;
20.}
21.}
Whichofthesestatementsistrue?
b
A.Thecodewillnotcompilecorrectlybecauseline19istryingtocallamethodthatdoesnotexistfortheclassTest.
B.Thecodedoesnotcompilebecauseofline12
C.Thecodedoesnotcompilebecauseofline14
D.Thereisnoambiguityastothereutrntypeinline12;therefore,thiscodewillcompileandoutputadoublevalue
greaterthanorequalto0andlessthan100.
E.ThiscodewillnotcompilebecausethegetNumber（）methodsintheTestclassmustallhavereturntypesofdouble.
8.Given:
1.publicclassA{
2.publicstaticvoidmain（String[]args）{
3.newA（）.printResult（1,"abc",4）;
4.}
5.privatevoidprintResult（inta,longb,intc）{
6.System.out.println（a+b+c）;
7.}
8.privatevoidprintResult（longa,Stringb,intc）{
9.System.out.println（a+b+c）;
10.}
11.}
Whichofthesestatementsistrue?
b
A.ThecodewillnotcompilecorrectlybecausealongandaStringmaynotbeaddedtogetherinline9.
B.Thecodewillcompileandrunandwilldisplay1abc4inthestandardoutput.
B.Thecodewillcompileandrunandwilldisplay11234inthestandardoutput.
D.ThecodewillcompileandwillthrowaNumberFormatException.
9.Whenasubclassmethodhasthesamename,parameterlist,andreturntypeasamethodintheparentclass,thismethodissaidtobewhat?
d
A.Extended
B.Overloaded
C.Overextended
D.Overridden/*¸²¸Ç*/
10.Whichofthefollowingmustmatchexactlyforoverloadedmethodstocompilecorreclty?
（Choosethatallapply）d
A.Theparameterlist
B.Thereturntype
C.Theexceptionthrown
D.Noneoftheabove
11.Given:
1.publicclassTest{
2.publicstaticvoidmain（String[]args）{
3.newTest（）.foo（1,2）;
4.}
5.privatevoidfoo（inta,intb）{
6.System.out.println（"int"）;
7.}
8.privatevoidfoo（longa,intb）{
9.System.out.println（"long"）;
10.}
11.}
Whatwillhappenwhenyoucompileandrunthisprogram?
a
A.Thecodewillcompileandrun,anddisplayint.
B.Thecodewillcompileandrun,anddisplaylong.
C.Thecodewillnotcompile.
D.Thecodewillcompile,butthrowaruntimeexceptionwhenexecuted.
12.Given:
1.publicclassParent{
2.publicvoidexecute（）throwsException{
3.//bodyomitted
4.}
5.}
6.publicclassChildextendsParent{
7.privatevoidexecute（）throwsClassCastException{
8.//bodyomitted
9.}
10.}
Whatwillhappenwhenyoucompilethisprogram?
a
A.Theprogramwillcompilesuccessfully.
B.Theprogramwillnotcompilebecausetheexecute（）inthesubclassthrowsadifferentexceptionthanintheparentclass.
C.Theprogramwillnotcompilebecausetheexecute（）inthesubclasshaslessaccessibilitythanintheparentclass.
D.Theprogramwillnotcompilebecausetheexecute（）inthesubclasshaslessaccessibliityandthrowsadifferentexceptionthanin
theparentclass.
13.Given:
1.publicclassA{
2.publicvoidbaz（）{
3.System.out.println（"A"）;
4.}
5.}
6.publicclassBextendsA{
7.publicstaticvoidmain（String[]args）{
8.Aa=newB（）;
9.a.baz（）;
10.}
11.publicvodbaz（）{
12.System.out.println（"B"）;
13.}
14.}
Whatwillhappenwhenyoucompileandrunthisprogram?
b
A.Theprogramcompiles,runs,anddisplayAinthestandardoutput.
B.Theprogramcompiles,runs,anddisplayBinthestandardoutput.
C.Theprogramcompiles,butthrowsaruntimeexception.
D.Theprogramdoesnotcompile.
14.Given:
1.publicclassA{
2.publicstaticvoidmain（String[]args）{
3.newA（）.baz（1,2）;
4.}
5.privatevoidbaz（inta,intb）{
6.System.out.println（"baz"）;
7.}
8.privatevoidfoo（inta,intb）{
9.System.out.println（"first"）;
10.}
11.privatebooleanfoo（inta,intb）{
12.System.out.println（"second"）;
13.returntrue;
14.}
15.}
Whichofthefollowingstatementsistrue?
A.Theprogramcompiles,runs,anddisplaysfirstinthestandardoutput.
B.Theprogramcompiles,runs,anddisplayssecondinthestandardoutput.
C.Theprogramcompiles,runs,anddisplaysbazinthestandardoutput.
D.Theprogramdoesnotcompile.
15.Given:
1.publicclassTest{
2.protectedvoidstart（）throwsClassCastException{
3.//bodyomitted
4.}
5.}
6.
7.publicclassChildextendsTest{
8.publicvoidstart（）throwsException{
9.//bodyomitted
10.}
11.}
Whatwillhappenwhenyoucompilethisprogram?
A.Theprogramwillcompilesuccessfully.
B.Theprogramwillnotcompilebecausethestart（）inthesubclassthrowsadifferentexceptionthanintheparentclass.
C.Theprogramwillnotcompilebecausethestart（）inthesubclassispublic,whereasitisprotectedintheparentclass.
D.Theprogramwillnotcompilebecausethestart（）inthesubclasshasdifferentaccessibilityandthrowsadifferentexceptionthanintheparentclass.
16.Whentwoormoremethodsinthesameclasshavethesamename,theyaresaidtobewhat?
A.Animplementationdetail
B.Overridden
C.Aninterface
D.Overloaded
17.Given:
1.publicclassExample{
2.publicstaticvoidmain（String[]args）{
3.newExample（）.locate（1.0,2）;
4.}
5.privatevoidlocate（doublea,longb）{
6.System.out.println（"double-long"）;
7.}
8.privatevoidlocate（longa,intb）{
9.System.out.println（"long-int"）;
10.}
11.}
Whatwillhappenwhenyoucompileandrunthisprogram?
b
A.Thecodewillcompile,runanddisplaydouble-long.
B.Thecodewillcompile,runanddisplaylong-int.
C.Thecodewillnotcompile.
D.Thecodewillcompile,butthrowaruntimeexceptionwhenexecuted.
18.Given:
1.classSuperTest{
2.publicSuperTest（）{
3.System.out.println（"Super!
"）;
4.}
5.}
6.
7.classTestextendsSuperTest{
8.publicstaticvoidmain（String[]args）{
9.newTest（）;
10.}
11.publicTest（）{
12.super（）;
13.this（"Great!
"）;
14.}
15.
16.publicTest（Stringname）{
17.System.out.println（name）;
18.}
19.}
Whatistheresultofthiscode?
f/*thisºÍsuperÒª·ÅÔÚµÚÒ»ÐУ¬²»ÄÜÔÙÒ»Æð³öÏÖ*/
A.Great!
Super!
B.Super!
Great!
C.Super!
Super!
Great!
D.Great!
E.Super!
F.Thiscodewillnotcompile.
19.Given:
1.publicclassTest{
2.publicstaticvoidmain（String[]args）{
3.newTest（4）;
4.}
5.publicTest（）{
6.System.out.println（"okay"）;
7.}
8.publicTest（inti）{
9.
10.}
11.}
Whichofthefollowinglinesofcodeshouldbeinsertedatline11sothattheoutputoftheprogramisokay?
c
A.super（）;
B.this;
C.Test（）;
D.this（）;
E.super（）;
20.Given:
1.publicclass
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