java考试选择题ss本.docx
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java考试选择题ss本.docx
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java考试选择题ss本
Readthequestionscarefully
Ihavetriedtomakethequestionsunambiguous(themeaningshouldbeobvious),butmakesureyouhavereadwhatIhavewrittennotwhatyouthinkImighthavewritten.Thusifitsays"Classescanbedeclaredwiththeprivatemodifier",itmeansItispossibletodeclareaclasswiththeprivatemodifierandnotthatallclassesinallsituationscanbedeclaredasprivate.EachquestionmayhaveoneormorecorrectAnswers.
臧廷杰
Questions
Question1)
Whichofthefollowinglineswillcompilewithoutwarningorerror.
1)floatf=1.3;
2)charc="a";
3)byteb=257;
4)booleanb=null;
5)inti=10;
Question2)
Whatwillhappenifyoutrytocompileandrunthefollowingcode
publicclassMyClass{
publicstaticvoidmain(Stringarguments[]){
amethod(arguments);
}
publicvoidamethod(String[]arguments){
System.out.println(arguments);
System.out.println(arguments[1]);
}
}
1)errorCan'tmakestaticreferencetovoidamethod.
2)errormethodmainnotcorrect
3)errorarraymustincludeparameter
4)amethodmustbedeclaredwithString
Becausemainisdefinedasstaticyouneedtocreateaninstanceoftheclassinordertocallanynon-staticmethods.
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Question3)
Whichofthefollowingwillcompilewithouterror
要先出现package
1)importjava.awt.*;
packageMypackage;
classMyclass{}
2)packageMyPackage;
importjava.awt.*;
classMyClass{}
3)/*Thisisacomment*/
packageMyPackage;
importjava.awt.*;
classMyClass{}
--------------------------------------------------------------------------------
臧廷杰
Question4)
Abytecanbeofwhatsize
1)-128to127
2)(-2power8)-1to2power8
3)-255to256
4)dependsontheparticularimplementationoftheJavaVirtualmachine
--------------------------------------------------------------------------------
Question5)
Whatwillbeprintedoutifthiscodeisrunwiththefollowingcommandline?
Javamyproggoodmorning;
publicclassmyprog{
publicstaticvoidmain(Stringargv[])
{
System.out.println(argv[2]);
}
}
1)myprog
2)good
3)morning
4)Exceptionraised:
"java.lang.ArrayIndexOutOfBoundsException:
2"
--------------------------------------------------------------------------------
Question6)
Whichofthefollowingarekeywordsorreserved(预定义)wordsinJava?
1)if
2)then
3)goto
4)while
5)case
--------------------------------------------------------------------------------
Question7)
Whichofthefollowingarelegalidentifiers(标识符)臧廷杰
1)2variable
2)variable2
3)_whatavariable
4)_3_
5)$anothervar
6)#myvar
--------------------------------------------------------------------------------
Question8)
Whatwillhappenwhenyoucompileandrunthefollowingcode?
publicclassMyClass{
staticinti;
publicstaticvoidmain(Stringargv[]){
System.out.println(i);
}
}
局部变量(在函数内部)必须先初始化,类级别的可以不初始化
Classlevelvariablesarealwaysinitialisedtodefaultvalues.Inthecaseofanintthiswillbe0.Methodlevelvariablesarenotgivendefaultvaluesandifyouattempttouseonebeforeithasbeeninitialiseditwillcausethe
ErrorVariableimaynothavebeeninitialized
1)ErrorVariableimaynothavebeeninitialized
2)null
3)1
4)0
--------------------------------------------------------------------------------
Question9)
Whatwillhappenifyoutrytocompileandrunthefollowingcode?
publicclassQ{
publicstaticvoidmain(Stringargv[]){
intanar[]=newint[]{1,2,3};
System.out.println(anar[1]);
}
}
1)1
2)Erroranarisreferencedbeforeitisinitialized
3)2
4)Error:
sizeofarraymustbedefined
--------------------------------------------------------------------------------
Question10)
Whatwillhappenifyoutrytocompileandrunthefollowingcode?
publicclassQ{
publicstaticvoidmain(Stringargv[]){
intanar[]=newint[5];
System.out.println(anar[0]);
}
}
1)Error:
anarisreferencedbeforeitisinitialized
2)null
3)0
4)5
--------------------------------------------------------------------------------
Question11)
Whatwillbetheresultofattemptingtocompileandrunthefollowingcode?
abstractclassMineBase{
abstractvoidamethod();
staticinti;
}
publicclassMineextendsMineBase{
publicstaticvoidmain(Stringargv[]){
int[]ar=newint[5];
for(i=0;i System.out.println(ar[i]); } } Anyclassderivedfromanabstractclassmusteitherdefinealloftheabstractmethodsorbedeclaredabstractitself. 1)asequenceof50'swillbeprinted 2)Error: arisusedbeforeitisinitialized 3)ErrorMinemustbedeclaredabstract 4)IndexOutOfBoundesError -------------------------------------------------------------------------------- Question12) Whatwillbeprintedoutifyouattempttocompileandrunthefollowingcode? inti=1; switch(i){ case0: System.out.println("zero"); break; case1: System.out.println("one"); case2: System.out.println("two"); default: System.out.println("default"); } 1)one 2)one,default 3)one,two,default 4)default -------------------------------------------------------------------------------- Question13) Whatwillbeprintedoutifyouattempttocompileandrunthefollowingcode? inti=9; switch(i){ default: System.out.println("default"); case0: System.out.println("zero"); break; case1: System.out.println("one"); case2: System.out.println("two"); } 1)default 2)default,zero 3)errordefaultclausenotdefined 4)nooutputdisplayed -------------------------------------------------------------------------------- Question14) Whichofthefollowinglinesofcodewillcompilewithouterror 1)inti=0; if(i){ System.out.println("Hello"); } 2)booleanb=true; booleanb2=true; if(b==b2){ System.out.println("Sotrue"); } 3)inti=1; intj=2; if(i==1||j==2)System.out.println("OK"); 4)inti=1; intj=2;i f(i==1&|j==2)System.out.println("OK"); -------------------------------------------------------------------------------- Question15) Whatwillbeoutputifyoutrytocompileandrunthefollowingcode,butthereis nofilecalledHello.txtinthecurrentdirectory? . importjava.io.*; publicclassMine{ publicstaticvoidmain(Stringargv[]){ Minem=newMine(); System.out.println(m.amethod()); } publicintamethod(){ try{ FileInputStreamdis=newFileInputStream("Hello.txt"); }catch(FileNotFoundExceptionfne){ System.out.println("Nosuchfilefound"); return-1; }catch(IOExceptionioe){} finally{ System.out.println("Doingfinally"); } return0; } } 1)Nosuchfilefound 2Nosuchfilefound,-1 3)Nosuchfilefound,Doingfinally,-1 4)0 -------------------------------------------------------------------------------- Question16) Whichofthefollowingstatementsaretrue? 1)Methodscannotbeoverridentobemoreprivate 2)staticmethodscannotbeoverloaded Staticmethodscannotbeoverridenbuttheycanbeoverloaded 3)privatemethodscannotbeoverloaded 4)Anoverloadedmethodcannotthrowexceptionsnotcheckedinthebaseclass -------------------------------------------------------------------------------- Question17) Whatwillhappenifyouattempttocompileandrunthefollowingcode? classBase{} classSubextendsBase{} classSub2extendsBase{} publicclassCEx{ publicstaticvoidmain(Stringargv[]){ Baseb=newBase(); Subs=(Sub)b; } } 1)Compileandrunwithouterror 2)CompiletimeException 3)RuntimeException -------------------------------------------------------------------------------- Question18) Whichofthefollowingstatementsaretrue? 1)System.out.println(-1>>>2);willoutputaresultlargerthan10无符号右移 2)System.out.println(-1>>2);willoutputapositivenumber输出-1 3)System.out.println(2>>1);willoutputthenumber1 4)System.out.println(1<<<2);willoutputthenumber4 -------------------------------------------------------------------------------- Question19) Whatwillhappenwhenyouattempttocompileandrunthefollowingcode? publicclassTuxextendsThread{ staticStringsName="vandeleur"; publicstaticvoidmain(Stringargv[]){ Tuxt=newTux(); t.piggy(sName); System.out.println(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" -------------------------------------------------------------------------------- Question20) Whatwillbedisplayedwhenyouattempttocompileandrunthefollowingcode //Codestart importjava.awt.*; publicclassButtextendsFrame{ publicstaticvoidmain(Stringargv[]){ ButtMyBut=newButt(); } Butt(){ ButtonHelloBut=newButton("Hello"); ButtonByeBut=newButton("Bye"); add(HelloBut); add(ByeBut); setSize(300,300); setVisible(true);}}//Codeend 1)Twobuttonssidebysideoccupyingalloftheframe,HelloontheleftandByeon theright 2)OnebuttonoccupyingtheentireframesayingHello 3)OnebuttonoccupyingtheentireframesayingBye 4)TwobuttonsatthetopoftheframeonesayingHellotheothersayingBye -------------------------------------------------------------------------------- Question21) Whatwillbeoutputbythefollowingcode? publicclassMyFor{ publicstaticvoidmain(Stringargv[])
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