Java试题4.docx

Java试题4.docx

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Java试题4

JavaText（四）

1.Whichofthefollowinglineswillcompilewithoutwarningorerror.

1）floatf=;

2）charc="a";

3）byteb=257;

4）booleanb=null;

5）inti=10;

2.Whatwillhappenifyoutrytocompileandrunthefollowingcode

publicclassMyClass{

publicstaticvoidmain（Stringarguments[]）{

amethod（arguments）;

}

publicvoidamethod（String[]arguments）{

}

}

1）errorCan'tmakestaticreferencetovoidamethod.

2）errormethodmainnotcorrect

3）errorarraymustincludeparameter

4）amethodmustbedeclaredwithString

3.Whichofthefollowingwillcompilewithouterror

1）import.*;

packageMypackage;

classMyclass{}

2）packageMyPackage;

import.*;

classMyClass{}

3）/*Thisisacomment*/

packageMyPackage;

import.*;

classMyClass{}

4.Whatwillbeprintedoutifthiscodeisrunwiththefollowingcommandline

javamyproggoodmorning

publicclassmyprog{

publicstaticvoidmain（Stringargv[]）

{

}

}

1）myprog

2）good

3）morning

4）Exceptionraised:

"2"

5.Whatwillhappenwhenyoucompileandrunthefollowingcode

publicclassMyClass{

staticinti;

publicstaticvoidmain（Stringargv[]）{

}

}

1）ErrorVariableimaynothavebeeninitialized

2）null

3）1

4）0

6.Whatwillhappenifyoutrytocompileandrunthefollowingcode

publicclassQ{

publicstaticvoidmain（Stringargv[]）{

intanar[]=newint[]{1,2,3};

}

}

1）1

2）Erroranarisreferencedbeforeitisinitialized

3）2

4）Error:

sizeofarraymustbedefined

7.Whatwillhappenifyoutrytocompileandrunthefollowingcode

publicclassQ{

publicstaticvoidmain（Stringargv[]）{

intanar[]=newint[5];

}

}

1）Error:

anarisreferencedbeforeitisinitialized

2）null

3）0

4）5

8.Whatwillbetheresultofattemptingtocompileandrunthefollowingcode

abstractclassMineBase{

abstractvoidamethod（）;

staticinti;

}

publicclassMineextendsMineBase{

publicstaticvoidmain（Stringargv[]）{

int[]ar=newint[5];

for（i=0;i<;i++）

}

}

1）asequenceof50'swillbeprinted

2）Error:

arisusedbeforeitisinitialized

3）ErrorMinemustbedeclaredabstract

4）IndexOutOfBoundesError

9.Whatwillbeprintedoutifyouattempttocompileandrunthefollowingcode

inti=1;

switch（i）{

case0:

"zero"）;

break;

case1:

"one"）;

case2:

"two"）;

default:

"default"）;

}

1）one

2）one,default

3）one,two,default

4）default

10.Whichofthefollowinglinesofcodewillcompilewithouterror

1）inti=0;

if（i）{

"Hello"）;

}

2）booleanb=true;

booleanb2=true;

if（b==b2）{

"Sotrue"）;

}

3）inti=1;

intj=2;

if（i==1||j==2）

"OK"）;

4）inti=1;

intj=2;

if（i==1&|j==2）

"OK"）;

11.Whatwillbeoutputifyoutrytocompileandrunthefollowingcode,butthereisnofilecalledinthecurrentdirectory.

import.*;

publicclassMine

{

publicstaticvoidmain（Stringargv[]）

{

Minem=newMine（）;

}

publicintamethod（）

{

try

{

FileInputStreamdis

=newFileInputStream（""）;

}

catch（FileNotFoundExceptionfne）

{

"Nosuchfilefound"）;

return-1;

}

catch（IOExceptionioe）

{}

finally

{

"Doingfinally"）;

}

return0;

}

}

1）Nosuchfilefound

2Nosuchfilefound,-1

3）Nosuchfilefound,Doingfinally,-1

4）0

ofthefollowingstatementsaretrue

1）Methodscannotbeoverridentobemoreprivate

2）staticmethodscannotbeoverloaded

3）privatemethodscannotbeoverloaded

4）Anoverloadedmethodcannotthrowexceptionsnotcheckedinthebaseclass

willhappenifyouattempttocompileandrunthefollowingcode

classBase{}

classSubextendsBase{}

classSub2extendsBase{}

publicclassCEx{

publicstaticvoidmain（Stringargv[]）{

Baseb=newBase（）;

Subs=（Sub）b;

}

}

1）Compileandrunwithouterror

2）CompiletimeException

3）RuntimeException

ofthefollowingstatementsaretrue

1）-1>>>2）;willoutputaresultlargerthan10

2）-1>>>2）;willoutputapositivenumber

3）2>>1）;willoutputthenumber1

4）1<<<2）;willoutputthenumber4

willhappenwhenyouattempttocompileandrunthefollowingcode

publicclassTuxextendsThread{

staticStringsName="vandeleur";

publicstaticvoidmain（Stringargv[]）{

Tuxt=newTux（）;

（sName）;

}

publicvoidpiggy（StringsName）{

sName=sName+"wiggy";

start（）;

}

publicvoidrun（）{

for（inti=0;i<4;i++）{

sName=sName+""+i;

}

}

}

1）Compiletimeerror

2）Compilationandoutputof"vandeleurwiggy"

3）Compilationandoutputof"vandeleurwiggy0123"

4）Compilationandoutputofeither"vandeleur","vandeleur0","vandeleur01""vandaleur012"or"vandaleur0123"

willbedisplayedwhenyouattempttocompileandrunthefollowingcode

;

publicclassButtextendsFrame{

publicstaticvoidmain（Stringargv[]）{

ButtMyBut=newButt（）;

}

Butt（）{

ButtonHelloBut=newButton（"Hello"）;

ButtonByeBut=newButton（"Bye"）;

add（HelloBut）;

add（ByeBut）;

setSize（300,300）;

setVisible（true）;

}

}

4）Thestring"Dolly"willbeshownatthebottomoftheframe.

willbetheresultwhenyouattempttocompilethisprogram

publicclassRand{

publicstaticvoidmain（Stringargv[]）{

intiRand;

iRand=（）;

}

}

1）Compiletimeerrorreferringtoacastproblem

2）Arandomnumberbetween1and10

3）Arandomnumberbetween0and1

4）Acompiletimeerroraboutrandombeinganunrecognisedmethod

thefollowingcode

import.*;

publicclassTh{

publicstaticvoidmain（Stringargv[]）{

Tht=newTh（）;

（）;

}

publicvoidamethod（）{

try{

ioCall（）;

}catch（IOExceptionioe）{}

}

}

WhatcodewouldbemostlikelyforthebodyoftheioCallmethod

1）publicvoidioCall（）throwsIOException{

DataInputStreamdin=newDataInputStream;

（）;

}

2）publicvoidioCall（）throwIOException{

DataInputStreamdin=newDataInputStream;

（）;

}

3）publicvoidioCall（）{

DataInputStreamdin=newDataInputStream;

（）;

}

4）publicvoidioCallthrowsIOException（）{

DataInputStreamdin=newDataInputStream;

（）;

}

willhappenwhenyoucompileandrunthefollowingcode

publicclassScope{

privateinti;

publicstaticvoidmain（Stringargv[]）{

Scopes=newScope（）;

（）;

}YouaregoingtousetheGridBagLayoutmanagertocontrolthewaythebuttonsaresetout.HowwillyoumodifythewaytheGridBagLayoutactsinordertochangethespacingaroundthefirstbutton

1）CreateaninstanceoftheGridBagConstraintsclass,calltheweightx（）methodandthenpasstheGridBagConstraintsinstancewiththecomponenttothesetConstraintsmethodoftheGridBagLayoutclass.

2）CreateaninstanceoftheGridBagConstraintsclass,settheweightxfieldandthenpasstheGridBagConstraintsinstancewiththecomponenttothesetConstraintsmethodoftheGridBagLayoutclass.

3）CreateaninstanceoftheGridBagLayoutclass,settheweightxfieldandthencallthesetConstraintsmethodoftheGridBagLayoutClasswiththecomponentasaparameter.

4）CreateaninstanceoftheGridBagLayoutclass,callthesetWeightx（）methodandthenpasstheGridBagConstraintsinstancewiththecomponenttothesetConstraintsmethodoftheGridBagLayoutclass.

ofthefollowingcanyouperformusingtheFileclass

1）Changethecurrentdirectory

2）Returnthenameoftheparentdirectory

3）Deleteafile

4）Findifafilecontainstextorbinaryinformation

statementistrueofthefollowingcode

publicclassRpcraven{

publicstaticvoidmain（Stringargv[]）{

Pmcravenpm1=newPmcraven（"One"）;

（）;

Pmcravenpm2=newPmcraven（"Two"）;

（）;

}

}

classPmcravenextendsThread{

privateStringsTname="";

Pmcraven（Strings）{

sTname=s;

}

publicvoidrun（）{

for（inti=0;i<2;i++）{

try{

sleep（1000）;

}catch（InterruptedExceptione）{}

yield（）;

}

}

}

1）Compiletimeerror,classRpcravendoesnotimportOutputofOneOneTwoTwo

3）OutputofOneTwoOneTwo

4）Compilationbutnooutputatruntime

areconcernedthatyourprogrammayattempttousemorememorythanisavailable.ToavoidthissituationyouwanttoensurethattheJavaVirtualMachinewillrunitsgarbagecollectionjustbeforeyoustartacomplexroutine.Whatcanyoudotobecertainthatgarbagecollectionwillrunwhenyouwant.

1）Youcannotbecertainwhengarbagecollectionwillrun

2）Usethe（）methodtoforcegarbagecollection

3）Ensurethatallthevariablesyourequiretobegarbagecollectedaresettonull

4）Usethe（）methodtoforcegarbagecollection

28、Whichstatementsaboutthegarbagecollectionaretrue

1.Theprogramdevelopermustcreateathreadtoberesponsibleforfreethememory.

2.Thegarbagecollectionwillcheckforandfreememorynolongerneeded.

3.Thegarbagecollectionallowtheprogramdevelopertoexplicityandimmediatelyfreethememory.

4.Thegarbagecollectioncanfreethememoryusedjavaobjectatexpecttime.

havethesefilesinthesamedirectory.Whatwillhappenwhenyouattempttocompileandrunifyouhavenotalreadycompiled

//

packageBase;

classBase{

protectedvoidamethod（）{

"amethod"）;

}//Endofamethod

}//Endofclassbase

packageClass1;

//

publicclassClass1extendsBase{

publicstaticvoidmain（Stringargv[]）{

Baseb=newBase（）;

（）;

}//Endofmain

}//EndofClass1

1）CompileError:

MethodsinBasenotfound

2）CompileError:

Unabletoaccessprotectedmethodinbaseclass

3）Compilationfollowedbytheoutput"amethod"

4）Compileerror:

Superclassofclassnotfound

willhappenwhenyouattempttocompileandrunthefollowingcode

classBase{

privatevoidamethod（intiBas