javaSCJP.docx
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javaSCJP
question1）
whatwillhappenwhenyouattempttocompileandrunthiscode?
abstractclassbase{
abstractpublicvoidmyfunc（）;
publicvoidanother（）{
system.out.println（"anothermethod"）;
}
}
publicclassabsextendsbase{
publicstaticvoidmain（stringargv[]）{
absa=newabs（）;
a.amethod（）;
}
publicvoidmyfunc（）{
system.out.println（"myfunc"）;
}
publicvoidamethod（）{
myfunc（）;
}
}
1）thecodewillcompileandrun,printingoutthewords"myfunc"
2）thecompilerwillcomplainthatthebaseclasshasnonabstractmethods
3）thecodewillcompilebutcomplainatruntimethatthebaseclasshasnonabstractmethods
4）thecompilerwillcomplainthatthemethodmyfuncinthebaseclasshasnobody,nobodyatalltoloooveit
question2）
whatwillhappenwhenyouattempttocompileandrunthiscode?
publicclassmymain{
publicstaticvoidmain（Stringargv）{
System.out.println（"hellocruelworld"）;
}
}
1）thecompilerwillcomplainthatmainisareservedwordandcannotbeusedforaclass
2）thecodewillcompileandwhenrunwillprintout"hellocruelworld"
3）thecodewillcompilebutwillcomplainatruntimethatnoconstructorisdefined
4）thecodewillcompilebutwillcomplainatruntimethatmainisnotcorrectlydefined
question5）
whymightyoudefineamethodasnative?
1）togettoaccesshardwarethatjavadoesnotknowabout
2）todefineanewdatatypesuchasanunsignedinteger
3）towriteoptimisedcodeforperformanceinalanguagesuchasc/c++
4）toovercomethelimitationoftheprivatescopeofamethod
question6）
whatwillhappenwhenyouattempttocompileandrunthiscode?
classbase{
publicfinalvoidamethod（）{
System.out.println（"amethod"）;
}
}
publicclassfinextendsbase{
publicstaticvoidmain（Stringargv[]）{
baseb=newbase（）;
b.amethod（）;
}
}
1）compiletimeerrorindicatingthataclasswithanyfinalmethodsmustbedeclaredfinalitself
2）compiletimeerrorindicatingthatyoucannotinherit（继承）fromaclasswithfinalmethods
3）runtimeerrorindicatingthatbaseisnotdefinedasfinal
4）successincompilationandoutputof"amethod"atruntime
question7）
whatwillhappenwhenyouattempttocompileandrunthiscode?
publicclassmod{
publicstaticvoidmain（Stringargv[]）{
}
publicstaticnativevoidamethod（）;
}
1）erroratcompilation:
nativemethodcannotbestatic
2）erroratcompilationnativemethodmustreturnvalue
3）compilationbuterroratruntimeunlessyouhavemadecodecontainingnativeamethodavailable
4）compilationandexecutionwithouterror
question8）
whatwillhappenwhenyouattempttocompileandrunthiscode?
privateclassbase{}
publicclassvis{
transientintival;
publicstaticvoidmain（Stringelephant[]）{
}
}
1）compiletimeerror:
basecannotbeprivate
2）compiletimeerrorindicatingthatanintegercannotbetransient
3）compiletimeerrortransientnotadatatype
4）compiletimeerrormalformedmainmethod
question9）
whathappenswhenyouattempttocompileandrunthesetwofilesinthesamedirectory?
//filep1.java
packagemypackage;
classp1{
voidafancymethod（）{
system.out.println（"whatafancymethod"）;
}
}
//filep2.java
publicclassp2extendsp1{
publicstaticvoidmain（Stringargv[]）{
p2p2=newp2（）;
p2.afancymethod（）;
}
}
1）bothcompileandp2outputs"whatafancymethod"whenrun
2）neitherwillcompile
3）bothcompilebutp2hasanerroratruntime
4）p1compilescleanlybutp2hasanerroratcompiletime
question10）
youwanttofindoutthevalueofthelastelementofanarray.youwritethefollowingcode.whatwillhappenwhenyoucompileandrunit.?
publicclassmyar{
publicstaticvoidmain（Stringargv[]）{
int[]i=newint[5];
System.out.println（i[5]）;
}
}
1）anerroratcompiletime
2）anerroratruntime
3）thevalue0willbeoutput
4）thestring"null"willbeoutput
question18）
whatwillhappenwhenyouattempttocompileandrunthefollowingcode?
publicclassbgroundextendsthread{
publicstaticvoidmain（stringargv[]）{
bgroundb=newbground（）;
b.run（）;
}
publicvoidstart（）{
for（inti=0;i<10;i++）{
system.out.println（"valueofi="+i）;
}
}
}
1）acompiletimeerrorindicatingthatnorunmethodisdefinedforthethreadclass
2）aruntimeerrorindicatingthatnorunmethodisdefinedforthethreadclass
3）cleancompileandatruntimethevalues0to9areprintedout
4）cleancompilebutnooutputatruntime
question25）
whatwillhappenwhenyouattempttocompileandrunthefollowingcode
publicclasshope{
publicstaticvoidmain（Stringargv[]）{
hopeh=newhope（）;
}
protectedhope（）{
for（inti=0;i<10;i++）{
System.out.println（i）;
}
}
}
1）compilationerror:
constructorscannotbedeclaredprotected
2）runtimeerror:
constructorscannotbedeclaredprotected
3）compilationandrunningwithoutput0to10
4）compilationandrunningwithoutput0to9
question26）
whatwillhappenwhenyouattempttocompileandrunthefollowingcode
publicclassmyswitch{
publicstaticvoidmain（Stringargv[]）{
myswitchms=newmyswitch（）;
ms.amethod（）;
}
publicvoidamethod（）{
intk=10;
switch（k）{
default:
//putthedefaultatthebottom,nothere
system.out.println（"thisisthedefaultoutput"）;
break;
case10:
system.out.println（"ten"）;
case20:
system.out.println（"twenty"）;
break;
}
}
}
1）noneoftheseoptions
2）compiletimeerrortargetofswitchmustbeanintegraltype
3）compileandrunwithoutput"thisisthedefaultoutput"
4）compileandrunwithoutputofthesingleline"ten"
question28）
whatwillhappenwhenyouattempttocompileandrunthefollowingcode
publicclassas{
inti=10;
intj;
charz=1;
booleanb;
publicstaticvoidmain（Stringargv[]）{
asa=newas（）;
a.amethod（）;
}
publicvoidamethod（）{
System.out.println（j）;
System.out.println（b）;
}
}
1）compilationsucceedsandatruntimeanoutputof0andfalse
2）compilationsucceedsandatruntimeanoutputof0andtrue
3）compiletimeerrorbisnotinitialised
4）compiletimeerrorzmustbeassignedacharvalue
question29）
whatwillhappenwhenyouattempttocompileandrunthefollowingcodewiththecommandline"hellothere"
publicclassarg{
string[]myarg;
publicstaticvoidmain（stringargv[]）{
myarg=argv;
}
publicvoidamethod（）{
System.out.println（argv[1]）;
}
}
1）compiletimeerror
2）compilationandoutputof"hello"
3）compilationandoutputof"there"
4）noneoftheabove
question30）
whatwillhappenwhenyouattempttocompileandrunthefollowingcode
publicclassstreq{
publicstaticvoidmain（stringargv[]）{
streqs=newstreq（）;
}
privatestreq（）{
strings="marcus";
strings2=newstring（"marcus"）;
if（s==s2）{
system.out.println（"wehaveamatch"）;
}else{
system.out.println（"notequal"）;
}
}
}
1）compiletimeerrorcausedbyprivateconstructor
2）outputof"wehaveamatch"
3）outputof"notequal"
4）compiletimeerrorbyattemptingtocomparestringsusing==
question32）
whatwillhappenwhenyouattempttocompileandrunthisprogram
publicclassouter{
publicstringname="outer";
publicstaticvoidmain（stringargv[]）{
inneri=newinner（）;
i.showname（）;
}//endofmain
privateclassinner{
stringname=newstring（"inner"）;
voidshowname（）{
system.out.println（name）;
}
}//endofinnerclass
}
1）compileandrunwithoutputof"outer"
2）compileandrunwithoutputof"inner"
3）compiletimeerrorbecauseinnerisdeclaredasprivate
4）compiletimeerrorbecauseofthelinecreatingtheinstanceofinner
question34）
whichoptionmostfullydescribeswillhappenwhenyouattempttocompileandrunthefollowingcode
publicclassmyar{
publicstaticvoidmain（stringargv[]）{
myarm=newmyar（）;
m.amethod（）;
}
publicvoidamethod（）{
staticinti;
system.out.println（i）;
}
}
1）compilationandoutputofthevalue0
2）compiletimeerrorbecauseihasnotbeeninitialized
3）compilationandoutputofnull
4）compiletimeerror
question35）
whichofthefollowingwillcompilecorrectly
1）shortmyshort=99s;
2）stringname='excellenttutorialmrgreen';
3）charc=17c;
4）intz=015;
question38）
giventhefollowingmainmethodinaclasscalledcycleandacommandlineof
javacycleonetwo
whatwillbeoutput?
publicstaticvoidmain（stringbicycle[]）{
system.out.println（bicycle[0]）;
}
1）noneoftheseoptions
2）cycle
3）one
4）two
question41）
giventhefollowingcode
classbase{}
publicclassmycastextendsbase{
staticbooleanb1=false;
staticinti=-1;
staticdoubled=10.1;
publicstaticvoidmain（stringargv[]）{
mycastm=newmycast（）;
baseb=newbase（）;
//here
}
}
whichofthefollowing,ifinsertedatthecomment//herewillallowthecodetocompileandrunwithouterror
1）b=m;
2）m=b;
3）d=i;
4）b1=i;
question45）
whatwillhappenwhenyouattempttocompileandrunthefollowingcode
intoutput=10;
booleanb1=false;
if（（b1==true）&&（（output+=10）==20））{
system.out.println（"weareequal"+output）;
}else
{
system.out.println（"notequal!
"+output）;
}
1）compileerror,attemptingtopeformbinarycomparisononlogicaldatatype
2）compilationandoutputof"weareequal10"
3）compilationandoutputof"notequal!
20"
4）compilationandoutputof"notequal!
10"
question48）
giventhefollowingvariables
charc='c';
inti=10;
doubled=10;
longl=1;
strings="hello";
whichofthefollowingwillcompilewithouterror?
1）c=c+i;
2）s+=i;
3）i+=s;
4）c+=s;
question51）
giventhefollowingcodewhatwillbetheoutput?
classvalhold{
pub
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