Java试题及答案英文版.docx
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Java试题及答案英文版
1．Whichtwodemonstratean“isa”relationship?
（ChooseTwo）
A.publicinterfacePerson{}
publicclassEmployeeextendsPerson{}
B.publicinterfaceShape{}
publicclassEmployeeextendsShape{}
C.publicinterfaceColor{}
publicclassEmployeeextendsColor{}
D.publicclassSpecies{}
publicclassAnimal{privateSpeciesspecies;}
E.interfaceComponent{}
ClassContainerimplementsComponent（
PrivateComponent[]children;
Answer:
de
2.Given:
1.packagefoo;
2.
3.publicclassOuter（
4. publicstaticclassInner（
5. ）
6.）
Whichstatementistrue?
A.AninstanceoftheInnerclasscanbeconstructedwith“newOuter.Inner（）”
B.Aninstanceoftheinnerclasscannotbeconstructedoutsideofpackagefoo
C.Aninstanceoftheinnerclasscanonlybeconstructedfromwithintheouterclass
D.Fromwithinthepackagebar,aninstanceoftheinnerclasscanbeconstructedwith“newinner（）”
Answer:
c
3．Exhibit：
1publicclassenclosinggone{
2publicclassinsideone{}
3}
4publicclassinertest{
5publicstaticvoidmain（String[]args）{
6enclosingoneeo=newenclosingone（）;
7//insertcodehere
8}
}
Whichstatementatline7constructsaninstanceoftheinnerclass?
A.InsideOneei=eo.newInsideOne（）;
B.B.Eo.InsideOneei=eo.newInsideOne（）;
CInsideOneei=EnclosingOne.newInsideOne（）;
D.EnclosingOneInsideOneei=eo.newInsideOne（）;
Answer:
a
C.4.
D.1）classSuper{
E.2）publicfloatgetNum（）{return3.0f;}
F.3）}
G.4）
H.5）publicclassSubextendsSuper{
I.6）
J.7）}
K.whichmethod,placedatline6,willcauseacompilererror?
L.A.publicfloatgetNum（）{return4.0f;}
M.B.publicvoidgetNum（）{}
N.C.publicvoidgetNum（doubled）{}
O.D.publicdoublegetNum（floatd）{return4.0d;}
Answer:
B
5.
1）publicclassFoo{
2）publicstaticvoidmain（Stringargs[]）{
3）try{return;}
4）finally{System.out.println（"Finally"）;}
5）}
6）}
whatistheresult?
A.Theprogramrunsandprintsnothing.
B.Theprogramrunsandprints“Finally”.
C.Thecodecompiles,butanexceptionisthrownatruntime.
D.Thecodewillnotcompilebecausethecatchblockismissing.
Answer:
b
6．
//pointX
publicclassFoo{
publicstaticvoidmain（String[]args）{
PrintWriterout=newPrintWriter（newjava.io.OutputStreamWriter（System.out）,true）;
out.println（"Hello"）;
}
}
whichstatementatpointXonline1allowsthiscodetocompileandrun?
A.importjava.io.PrintWriter B.includejava.io.PrintWriter
C.importjava.io.OutputStreamWriter D.includejava.io.OutputStreamWriter
E.Nostatementisneeded
Answer:
a
7.whichthreearevaliddeclaractionofafloat?
A.floatfoo=-1;
B.floatfoo=1.0;
C.floatfoo=42e1;
D.floatfoo=2.02f;
E.floatfoo=3.03d;
F.floatfoo=0x0123;
Answer:
adf
8.
intindex=1;
intfoo[]=newint[3];
intbar=foo[index];
intbaz=bar+index;
whatistheresult?
A.bazhasavalueof0
B.bazhasvalueof1
C.bazhasvalueof2
D.anexceptionisthrown
E.thecodewillnotcompile
Answer:
b
9．
1）inti=1,j=10;
2）do{
3）if（i++>--j）continue;19283746
4）}while（i<5）;
AfterExecution,whatarethevalueforiandj?
A.i=6j=5
B.i=5j=5
C.i=6j=4
D.i=5j=6
E.i=6j=6
Answer:
d
10．
1）publicclassX{
2）publicObjectm（）{
3）Objecto=newFloat（3.14F）;
4）Object[]oa=newObject[1];
5）oa[0]=o;
6）o=null;
7）oa[0]=null;
8）System.out.println（oa[0]）;
9）}
10）}
whichlineistheearliestpointtheobjectareferedisdefinitelyelibiletobegarbagecollectioned?
A.Afterline4
B.Afterline5
C.Afterline6
D.Afterline7
E.Afterline9
Answer:
d
11．
1.publicclassX{
2.publicstaticvoidmain（String[]args）{
3.Objecto1=newObject（）;
4.Objecto2=o1;
5.if（o1.equals（o2））{
6.System.out.println（"Equal"）;
7.}
8.}
9.}
Whatistheresult?
A.Theprogramrunsandprintsnothing.
B.Theprogramrunsandprints"Equal".
C.Anerroratline5causescompilationtofail.
D.Theprogramrunsbutabortswithanexception.
Answer:
B
12．
1）publicclassTest{
2）publicstaticvoidadd3（Integeri）{
3）intval=i.intValue（）;
4）val+=3;
5）i=newInteger（val）;
6）}
7）publicstaticvoidmain（Stringargs[]）{
8）Integeri=newInteger（0）;
9）add3（i）;
10）System.out.println（i.intValue（））;
11）}
12）}
whatistheresult?
A.compilefail
B.printout"0"
C.printout"3"
D.compilesuccededbutexceptionatline3
Answer:
b
13.
Given:
1.publicclassFoo{
2.publicvoidmain（String[]args）{
3.system.out.printIn（“HelloWorld.”）;
4.}
5.}
Whatistheresult?
A.Anexceptionisthrown.
B.Thecodedoesnotcompile.
C.“HelloWorld.”isprintedtotheterminal.
D.Theprogramexitswithoutprintinganything.
AnswerA
14．Given:
13.publicclassFoo{
14.publicstaticvoidmain（String[]args）{
15.StringBuffera=newStringBuffer（“A”）;
16.StringBufferb=newStringBuffer（“B”）;
17.operate（a,b）;
18.system.out.printIn{a+“,”+b};
19.）
20.staticvoidoperate（StringBufferx,StringBuffery）{
21.y.append（x）;
22.y=x;
23.）
24.}
Whatistheresult?
A.Thecodecompilesandprints“A,B”.
B.Thecodecompilesandprints“A,BA”.
C.Thecodecompilesandprints“AB,B”.
D.Thecodecompilesandprints“AB,AB”.
E.Thecodecompilesandprints“BA,BA”.
F.Thecodedoesnotcompilebecause“+”cannotbeoverloadedforstringBuffer.
AnswerB
15．
Given:
1.publicclassSyncTest{
2.privateintx;
3.privateinty;
4.publicsynchronizedvoidsetX（inti）（x=1;）
5.publicsynchronizedvoidsetY（inti）（y=1;）
6.publicsynchronizedvoidsetXY（int1）（setX（i）;setY（i）;）
7.publicsynchronizedBooleancheck（）（returnx!
=y;）
8.）
Underwhichconditionswillcheck（）returntruewhencalledfromadifferentclass?
A.Check（）canneverreturntrue.
B.Check（）canreturntruewhensetXYiscalledbymultiplethreads.
C.Check（）canreturntruewhenmultiplethreadscallsetXandsetYseparately.
D.Check（）canonlyreturntrueifSyncTestischangedtoallowxandytobesetseparately.
Answer:
A
16．
1）publicclassTest{
2）publicstaticvoidmain（String[]args）{
3）Stringfoo=args[1];
4）Sringbar=args[2];
5）Stringbaz=args[3];
6）}
7）}
javaTestRedGreenBlue
whatisthevalueofbaz?
A.bazhasvalueof""
B.bazhasvalueofnull
C.bazhasvalueof"Red"
D.bazhasvalueof"Blue"
E.bazhasvalueof"Green"
F.thecodedoesnotcompile
G.theprogramthrowanexception
Answer:
G
17．
1） interfaceFoo{
2） intk=0;
3） }
4）publicclassTestimplementsFoo{
5） publicstaticvoidmain（Stringargs[]）{
6） inti;
7） Testtest=newTest（）;
8） i=test.k;
9） i=Test.k;
10） i=Foo.k;
11） }
12）}
Whatistheresult?
A.Compilationsucceeds.
B.Anerroratline2causescompilationtofail.
C.Anerroratline9causescompilationtofail.
D.Anerroratline10causescompilationtofail.
E.Anerroratline11causescompilationtofail.
Answer:
a
18．
classBaseClass{
privatefloatx=1.0f;
privatefloatgetVar（）{returnx;}
}
classSubClassextendsBaseClass{
privatefloatx=2.0f;
//insertcode
}
whataretruetooverridegetVar（）?
A.floatgetVar（）{
B.publicfloatgetVar（）{
C.publicdoublegetVar（）{
D.protectedfloatgetVar（）{
E.publicfloatgetVar（floatf）{
Answer:
a,b,d
19．
Given:
inti=1,j=10;
do{
if（i>j）continue;
j--;
}while（++i<6）;
whatarethevaleofiandj?
A.i=6,j=5
B.i=5,j=5
C.i=6,j=4
D.i=5,j=6
E.i=6,j=6
Answer:
A
20．
byte[]array1,array2[]
bytearray3[][]
byte[][]array4
ifeachhasbeeninitialized,whichstatementwillcauseacompileerror?
A.array2=array1;
B.array2=array3;
C.array2=array4;
D.bothAandB
E.bothAandC
F.bothBandC
Answer:
a
21．
whichfourtypesofobjectscanbethrownuse"throws"?
A.Error
B.Event
C.Object
D.Excption
E.Throwable
F.RuntimeException
Answer:
A,D,E，F
22．
1）publicclassTest{
2）publicstaticvoidmain（String[]args）{
3）unsignedbyteb=0;
4）b--;
5）
6）}
7）}
whatisthevalueofbatline5?
A.-1B.255C.127D.compilefailE.compilesucceededbutrunerror
Answer:
d
23．
publicclassExceptionTest{
classTestExceptionextendsException{}
publicvoidrunTest（）throwsTestException{}
publicvoidtest（）/*pointx*/{
runTest（）;
}
}
Atpointx,whichcodecanbeaddontomakethecodecompile?
A.throwsException
B.catch（Exceptione）
C.throwsRuntimeException
D.catch（TestExceptione）
E.nocodeisnecessary
Answer:
A
24．
Stringfoo="blue";
boolean[]bar=newboolean[1];
if（bar[0]）{
foo="green";
}
whatisthevalueoffoo?
A.""B.nullC.blueD.green
Answer:
C
25．
whichtwoareequivalent?
A.3/2
B.3<2
C.3*4
D.3<<2
E.3*2^2
F.3<<<2
Answer:
c,d
26．
intindex=1;
String[]test=newString[3];
Stringfoo=test[index];
whatistheresultoffoo?
A.foohasthevalue“”
B.foohasthevaluenull
C.anexceptionisthrown
D.thecodewillnotcompile
Answer:
b
27．
whichtwoaretrue?
A.staticinnerclassrequiresastaticinitializer
B.Astaticinnerclassrequiresaninstanceoftheenclosingclass
C.Astaticinnerclasshasnoreferencetoaninstanceoftheenclosingclass
D.Astaticinnerclasshasaccessstothenon-staticmemberoftheotherclass
E.staticmembersofastaticinnerclasscanbereferencedusingtheclassnameofthestaticinnerclass
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