Java 认证模考试题.docx
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Java认证模考试题
Java 认证模考试题
［作者：
佚名 发表时间：
2004-5-2722:
14:
08 阅读：
331］
Java2TEST
Question:
1
Giventhefollowingcode:
classTest{
privateintm;
publicstaticvoidfun（）{
//somecode...
}
}
Howcanthemembervariablembeaccessibledirectlyinthemethodfun（）?
A.changeprivateintmtoprotectedintm
B.changeprivateintmtopublicintm
C.changeprivateintmtostaticintm
D.changeprivateintmtointm
Explanation:
Ifthevariablemischangedtobeastaticvariableitcanbeaccessibleinthemethodfun（）forthismethodisastaticmembermethod.
CorrectAnswer:
C1of60
Question:
2
Whichmethodsarecorrectoverloadingmethodsofthefollowingmethod:
publicvoidexample（）{...}
A.publicvoidexample（intm）{...}
B.publicintexample（）{...}
C.publicvoidexample2（）{...}
D.publicintexample（intm,floatf）{...}
Explanation:
Theoverloadingmethodsmusthavethesamenames.Ifonlythereturntypeofthemethodsaredifferentitissufficienttellthemethodsfromeachother.Theargumentsofthemethodsmustbedifferentenoughtodeterminewhichmethodtocall.
CorrectAnswer:
A,D2of60
Question:
3
Giventhefollowingfragmentofcode:
publicclassBase{
intw,x,y,z;
publicBase（inta,intb）{
x=a;y=b;
}
publicBase（inta,intb,intc,intd）{
//assignmentx=a,y=b
w=d;
z=c;
}
}
Whichexpressionscanbeusedatthepointof//assignmentx=a,y=b?
A.Base（a,b）;
B.x=a,y=b;
C.x=a;y=b;
D.this（a,b）;
Explanation:
Inthesecondconstructor,thecallthis（a,b）passescontroltheversionoftheconstructorthattakestwointarguments.
CorrectAnswer:
C,D3of60
Question:
4
Giventhefollowingdefinition:
Strings=story;
Whichofthefollowingexpressionsarelegal?
A.s+=books;
B.charc=s[1];
C.intlen=s.length;
D.Stringt=s.toLowerCase（）;
Explanation:
AnswerBisnotcorrectforStringisaclassandcan'Tbetreatedasanarrayofchar.AnswerCisnotcorrectfors.length（）shouldbeused,nots.length.
CorrectAnswer:
A,D4of60
Question:
5
Whatisthereturnvalueofthemain（）methodinJava?
A.String
B.int
C.char
D.void
Explanation:
Themain（）methodinJavareturnsvoid.
CorrectAnswer:
D5of60
Question:
6
WhicharethevalididentifiersinJava?
A.fieldname
B.super
C.3number
D.#number
E.$number
Explanation:
ValididentifiersinJavacanstartwithaletter,underscore（_）,ordollarsign（$）,butnotwithdigitsorothersigns.Andidentifierscannotbekeywords.
CorrectAnswer:
A,E6of60
Question:
7
WhicharevalidJavakeywords?
A.const
B.NULL
C.false
D.this
E.native
Explanation:
AllthekeywordsinJavaarelowercase.gotoandconstarekeywordsthatarenotusedinJavaprogramminglanguage.
CorrectAnswer:
A,C,D,E7of60
Question:
8
WhicharevalidintegralexpressionsinJava?
A.22
B.0x22
C.022
D.22H
Explanation:
InJavaintegralhasthreeforms:
decimal,octalandhexadecimal.Octalvaluesstartwithazeroandhexadecimalvaluesstartwith0x.
CorrectAnswer:
A,B,C8of60
Question:
9
Whichoneofthefollowingrangesofshortiscorrect?
Explanation:
Thelengthoftheshortdatais16bits.Therangeofshortis
Thelengthoftheshortdatais16bits.Therangeofshortis
CorrectAnswer:
D9of60
Question:
10
Whichoneofthefollowingrangesofbyteiscorrect?
CorrectAnswer:
B10of60
Question:
11
Giventhefollowingfragmentofcode,whatareresultsofiandjafterexecution?
inti=1;
intj;
j=i++;
A.1,1
B.1,2
C.2,1
D.2,2
Explanation:
Payattentiontothepositionoftheoperator++.Inthisquestion,firstjisassignedto1,thenthevalueofiisaddedto2.
CorrectAnswer:
C11of60
Question:
12
Whichofthefollowingstatementsaretrue?
A.>>isthearithmeticrightshiftoperator.
B.>>isthelogicalrightshiftoperator.
C.>>>isthearithmeticrightshiftoperator.
D.>>>isthelogicalrightshiftoperator.
Explanation:
TherearetworightshiftoperatorsinJava.Theyare>>and>>>.>>isthearithmetic（signed）rightshiftoperatorand>>>isthelogical（unsigned）rightshiftoperator.
CorrectAnswer:
A,D12of60
Question:
13
Whichofthefollowingassignmentsarelegal?
A.floata=2.0
B.doubleb=2.0
C.intc=2
D.longd=2
Explanation:
InJavathedefaultdatatypeoffloatingpointisdouble,notfloat.Theassignmentfromdoubletofloatrequiresanexplicitcast.
CorrectAnswer:
B,C,D13of60
Question:
14
Whichoneofthefollowingargumentsisthecorrectargumentofthemain（）method?
A.charargs[]
B.charargs[][]
C.Stringarg[]
D.Stringargs
Explanation:
Theargumentofthemain（）methodisanarrayofString.ThenonlyanswerCisanarrayofString.
CorrectAnswer:
C14of60
Question:
15
Whichoneofthefollowingiscorrecttocreateanarray?
A.floatf[][]=newfloat[6][6];
B.float[]f[]=newfloat[6][6];
C.floatf[][]=newfloat[][6];
D.float[][]f=newfloat[6][6];
E.float[][]f=newfloat[6][];
Explanation:
InJavathedeclarationformatallowsthesquarebracketstobeattheleftorrightofthevariablename.Butthenewfloat[][6]isillegal.
CorrectAnswer:
A,B,D,E15of60
Question:
16
Giventhefollowingexpression:
intm[]={0,1,2,3,4,5,6};
Whichresultofthefollowingexpressionsequalstothenumberofthearrayelements?
A.m.length（）
B.m.length
C.m.length（）+1
D.m.length+1
Explanation:
Thenumberofelementsinanarrayisstoredinthelengthattributeinthearrayobject.
CorrectAnswer:
B16of60
Question:
17
Giventhefollowingcommandtorunacorrectclass:
javaMyTestabc
Whichstatementsaretrue?
A.args[0]=MyTestabc
B.args[0]=MyTest
C.args[0]=a
D.args[1]='b'
Explanation:
Thethreeargumentsabcarestoredintheargs[]arrayofthemain（）method.Thenargs[0]=a,args[1]=b,args[2]=c.
CorrectAnswer:
C17of60
Question:
18
Giventhefollowingcode:
publicclassTest{
longa[]=newlong[10];
publicstaticvoidmain（Stringarg[]）{
System.out.println（a[6]）;
}
}
Whichstatementistrue?
A.Outputisnull.
B.Outputis0.
C.Whencompile,someerrorwilloccur.
D.Whenrunning,someerrorwilloccur.
Explanation:
Whenanarrayiscreatedthemembersofthearrayisinitialized.Inthiscasealltheelementsareinitializedtobe0.
CorrectAnswer:
B18of60
Question:
19
Giventhefollowingfragmentofcode:
booleanm=true;
if（m=false）
System.out.println（False）;
else
System.out.println（True）;
Whatistheresultoftheexecution?
A.False
B.True
C.None
D.Anerrorwilloccurwhenrunning.
Explanation:
=istheassignmentoperator.==isthecompareoperator.Inthisquestionthevalueoffalseisassignedtothevariablem.
CorrectAnswer:
A19of60
Question:
20
Giventhefollowingcode:
publicclassTest{
publicstaticvoidmain（Stringarg[]）{
inti=5;
do{
System.out.println（i）;
}while（--i>5）
System.out.println（“finished”）;
}
}
Whatwillbeoutputafterexecution?
A.5
B.4
C.6
D.Finished
E.None
Explanation:
Theexpressionsintheblockofdo/whileloopwillbeexecutedatleastonce.Iftheconditionofthisloopisnotmettheloopwillstopafteronceexecution,otherwise,itwillcontinuetoloopuntiltheconditionisnomet.
CorrectAnswer:
A,D20of60
Question:
21
Whatwillbeoutputafterexecutionofthefollowingcode:
outer:
for（inti=0;i<3;i++）
inner:
for（intj=0;j<2;j++）
{
if（j==1）continueouter;
System.out.println（j+?
and?
+i）;
}
A.0and0
B.0and1
C.0and2
D.1and0
E.1and1
F.1and2
G.2and0
H.2and1
I.2and2
Explanation:
Thecontinuestatementisusedtoskipoverandjumptotheendoftheloopbody.Thenifjequalsto1itwilljumptotheendoftheinnerloopbody.
CorrectAnswer:
A,B,C21of60
Question:
22
Giventhefollowingcode:
switch（m）
{
case0:
System.out.println（Condition0）;
case1:
System.out.println（Condition1）;
case2:
System.out.println（Condition2）;
case3:
System.out.println（Condition3）;break;
default:
System.out.println（OtherCondition）;
}
WhichvaluesofmwillcauseCondition2isoutput?
A.0
B.1
C.2
D.3
E.4
F.None
Explanation:
Intheblockofswitch,ifthereisnobreaksentenceinonecasethefollowingsentenceswillbeexecuted.
CorrectAnswer:
A,B,C22of60
Question:
23
WhichmethodiscalledwhenthebrowserreturnstothepagecontainingtheappletaftermovingtoanotherURL?
A.init（）
B.start（）
C.stop（）
D.destroy（）
Explanation:
Thestart（）runswhenevertheappletbecomesvisible,suchaswhenthebrowserreturnstothepagecontainingtheappletaftermovingtoanotherURLorthebrowserisrestoredafterbeingiconized.
CorrectAnswer:
B23of60
Question:
24
Ifathreadcallsthewait（）method,whichmethodscanmakeitcontinuetorun?
A.join（）
B.resume（）
C.notify（）
D.notifyAll（）
E.highprioritythreadisready
Explanation:
Ifathreadissuesawait（）callitwillpauseexecutionuntilanotherthreadissuesanotify（）ornotifyAll（）call.Thepairofthemethodsareprovidedforthreadcommunication.
CorrectAnswer:
C,D24of60
Question:
25
Whichmethodisusedtodefinetheexecutionbodyofathread?
A.start（）
B.init（）
C.run（）
D.main（）
E.synchronized（）
Explanation:
Thethreadswillalwaysbeginexecutingattherun（）method,whichcontainsthedef
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