System.out.println（s）;
}}
WhichofthefollowingwillbeincludedintheoutputStrings?
（Chooseallthatapply.）
A..e1
B..e2
C.=s
D.fly
E.Noneoftheabove.
F.Compilationfails.
G.Anexceptionisthrownatruntime.
2（10）.
aboutthethreejava.langclassesString,StringBuilder,andStringBufferaretrue?
（Chooseallthatapply.）
A.Allthreeclasseshavealength（）method.
B.ObjectsoftypeStringBufferarethread-safe.
C.Allthreeclasseshaveoverloadedappend（）methods.
D.The"+"isanoverloadedoperatorforallthreeclasses.
E.AccordingtotheAPI,StringBufferwillbefasterthanStringBuilderundermost
implementations.
F.Thevalueofaninstanceofanyofthesethreetypescanbemodifiedthroughvarious
methodsintheAPI.
3（13）Given:
classPolish{
publicstaticvoidmain（String[]args）{
intx=4;
StringBuffersb=newStringBuffer（"..fedcba"）;
sb.delete（3,6）;
sb.insert（3,"az"）;
if（sb.length（）>6）x=sb.indexOf（"b"）;
sb.delete（（x-3）,（x-2））;
System.out.println（sb）;
Whatistheresult?
A..faza
B..fzba
C...azba
D..fazba
E...fezba
F.Compilationfails.
4（22）
whatStringinstancemethodwouldreturntruewheninvokedlikethis
a.method（b）;
wherea="GROUNDhog"andb="groundHOG"
selectallanswers
A.equals（）
B.toLowercase（）
C.toUppercase（）
D.equalsIgnoreCase（）
E.Noneoftheabove
5（25）
Attheendofthesetwolinesofcode:
Strings="hypertext";
Stringt=s.subString（2,5）;
Whatdoestheobjectreferencetcontain?
A."yper"
B."ype"
C."pert"
D."per"
E."perte"
6（26）
Whichofhefollowingstatementswouldreturnfalse?
ifgiventhefollowingstatements
Strings=newString（"Newyear"）;
Strings1=newString（"newYear"）;
A.s==s1
B.s.equals（s1）
C.s=s1;
D.noneoftheabove
7（28）
Whichwillcompileandrunwithoutexception,generatetheoutput4247
A.classExample{
publicstaticvoidmain（String[]args）{
Strings="123456789";
s=（s-"123"）.replace（1,3,"24"）-"89";
System.out.println（s）;
}
}
B.classExample{
publicstaticvoidmain（String[]args）{
StringBuffers=newStringBuffer（"123456789"）;
s.delete（0,3）.replace（1,3,"24"）.delete（4,6）
System.out.println（s）;
}
}
C.classExample{
publicstaticvoidmain（String[]args）{
StringBuffers=newStringBuffer（"123456789"）;
s.substring（3,6）.delete（1,3）.insert（1,"24"）;
System.out.println（s）;
}
}
D.classExample{
publicstaticvoidmain（String[]args）{
StringBuilders=newStringBuilder（"123456789"）;
s.substring（3,6）.delete（1,2）.insert（1,"24"）;
System.out.println（s）;
}
}
8（29）
classExample{
publicstaticvoidmain（String[]args）{
Strings="ABCD";
s.concat（"E"）;
s.replace（'C','F'）;
System.out.println（s）;
}
}
whatwillbeprintedout?
A.CompilationErrorssaystheStringisimmutable
B.ABFDE
C.ABCDE
D.ABCD
9（33）
classExample{
publicstaticvoidmain（String[]args）{
Stringstr="Welcome";
str.concat（"Tojava"）;
System.out.println（str）;
}
}
whatwillbeprintedout?
A.theStringisimmutable,CompilationErrorsatline3
B.theStringisimmutable,RunExceptionatline3
C.Prints"Welcome"
D.prints"WelcomeTojava"
10.（39）
classExample{
publicstaticvoidmain（String[]args）{
Strings1=newString（"amit"）;
Strings2=s1.replace（'m','i'）;
s1.concat（"Poddar"）;
System.out.println（s1）;
System.out.println（（s1+s2）.charAt（5））;
}
}
whatwillbeprintedout?
A.CompilationError
B.amitPoddaro
C.amitPoddari
D.amiti
二、I/O、串行化
1
（2）Given:
importjava.io.*;
classPlayer{
Player（）{System.out.print（"p"）;}
}
classCardPlayerextendsPlayerimplementsSerializable{
CardPlayer（）{System.out.print（"c"）;}
publicstaticvoidmain（String[]args）{
CardPlayerc1=newCardPlayer（）;
try{
FileOutputStreamfos=newFileOutputStream（"play.txt"）;
ObjectOutputStreamos=newObjectOutputStream（fos）;
os.writeObject（c1）;
os.close（）;
FileInputStreamfis=newFileInputStream（"play.txt"）;
ObjectInputStreamis=newObjectInputStream（fis）;
CardPlayerc2=（CardPlayer）is.readObject（）;
is.close（）;
}catch（Exceptionx）{}
}
}
Whatistheresult?
A.pc
B.pcc
C.pcp
D.pcpc
E.Compilationfails.
F.Anexceptionisthrownatruntime.
2（3）
Given:
bwisareferencetoavalidBufferedWriter
Andthesnippet:
15.BufferedWriterb1=newBufferedWriter（newFile（"f"））;
16.BufferedWriterb2=newBufferedWriter（newFileWriter（"f1"））;
17.BufferedWriterb3=newBufferedWriter（newPrintWriter（"f2"））;
18.BufferedWriterb4=newBufferedWriter（newBufferedWriter（bw））;
Whatistheresult?
A.Compilationsucceeds.
B.Compilationfailsdueonlytoanerroronline15.
C.Compilationfailsdueonlytoanerroronline16.
D.Compilationfailsdueonlytoanerroronline17.
E.Compilationfailsdueonlytoanerroronline18.
F.Compilationfailsduetoerrorsonmultiplelines.
3（6）
importjava.io.*;
classKeyboard{}
publicclassComputerimplementsSerializable{
privateKeyboardk=newKeyboard（）;
publicstaticvoidmain（String[]args）{
Computerc=newComputer（）;
c.storeIt（c）;
}
voidstoreIt（Computerc）{
try{
ObjectOutputStreamos=newObjectOutputStream（
newFileOutputStream（"myFile"））;
os.writeObject（c）;
os.close（）;
System.out.println（"done"）;
}catch（Exceptionx）{System.out.println（"exc"）;}
}
}
Whatistheresult?
（Chooseallthatapply.）
A.exc
B.done
C.Compilationfails.
D.Exactlyoneobjectisserialized.
E.Exactlytwoobjectsareserialized.
4（7）
Giventhefewestfragmentspossible（andfillingthefewestslotspossible）,completethecode
belowsothattheclassbuildsadirectorynamed"dir3"andcreatesafilenamed"file3"inside
"dir3".Noteyoucanuseeachfragmenteitherzerooronetimes.
Code:
importjava.io.______________
classMaker{
publicstaticvoidmain（String[]args）{
_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
_________________________________
}}
Fragments:
File;FileDescriptor;FileWriter;Directory;
try{.createNewDir（）;FiledirFile
{}（Exceptionx）（"dir3"）;file
file.createNewFile（）;=newFile=newFile
dir（dir,"file3"）;（dir,file）;.createFile（）;
}catch（"dir3","file3"）;.mkdir（）;Filefile
Answer:
importjava.io.File;
classMaker{
publicstaticvoidmain（String[]args）{
try{
Filedir=newFile（"dir3"）;
dir.mkdir（）;
Filefile=newFile（dir,"file3"）;
file.createNewFile（）;
}catch（Exceptionx）{}
}}
5（12）
Given:
importjava.io.*;
classDirectories{
staticString[]dirs={"dir1","dir2"};
publicstaticvoidmain（String[]args）{
for（Stringd:
dirs）{
//insertcode1here
Filefile=newFile（path,args[0]）;
//insertcode2here
}
}
}
andthattheinvocation
javaDirectoriesfile2.txt
isissuedfromadirectorythathastwosubdirectories,"dir1"and"dir1",andthat"dir1"hasa
file"file1.txt"and"dir2"hasafile"file2.txt",andtheoutputis"falsetrue",which
set（s）ofcodefragmentsmustbeinserted?
（Chooseallthatapply.）
A.Stringpath=d;
System.out.print（file.exists（）+""）;
B.Stringpath=d;
System.out.print（file.isFile（）+""）;
C.Stringpath=File.separator+d;
System.out.print（file.exists（）+""）;
D.Stringpath=File.separator+d;
System.out.print（file.isFile（）+""）;
6（15）
Given:
importjava.io.*;
publicclassTestSer{
publicstaticvoidmain（String[]args）{
SpecialSerials=newSpecialSerial（）;
try{
ObjectOutputStreamos=newObjectOutputStream（
newFileOutputStream（"myFile"））;
os.writeObject（s）;os.close（）;
System.out.print（++s.z+""）;
ObjectInputStreamis=newObjectInputStream（
newFileInputStream（"myFile"））;
SpecialSerials2=（SpecialSerial）is.readObject（）;
is.close（）;
System.out.println（s2.y+""+s2.z）;
}catch（Exceptionx）{System.out.println（"exc"）;}
classSpecialSerialimplementsSerializable{
transientinty=7;
staticintz=9;
Whicharetrue?
（Chooseallthatapply.）
A.Compilationfails.
B.Theoutputis1009
C.Theoutputis10010
D.Theoutputis1079
E.Theoutputis10710
F.InordertoalterthestandarddeserializationprocessyouwouldoverridethereadObject（）
methodinSpecialSerial.
G.Inordertoalterthestandarddeserializationprocessyouwouldoverridethe
defaultReadObject（）methodinSpecialSerial.
7（3）Whatisresultwhenyoucompileandrunthefollowingcode?
importjava.io.*;
publicclassExample
{publicstaticvoidmain（String[]args）{
Filef=newFile（"hello.test"）;
try{
FileOutputStreamout=newFileOutputStream（f）;
}
catch（FileNotFoundExceptione）{}
}
}
A.Createanewfilenamed"hello.test"ifitdoesnotyetexit.Italsoopensthefilesoyoucanwritetoitandreadfromit
B.Createanewfilenamed"hello.test"ifitdoesnotyetexit.Thefileisnotopened
C.openafilenamed"hello.test"sothatyoucanwritetoitandreadfromit,butdoesnotcreatethefileifitdoesnotyetexit
D.openafilenamed"hello.test"sothatyoucanwritetoitbutcannotreadfromit
8（4）Whatisresultwhenyoucompileandrunthefollowingcode?
importjava.io.*;
publicclassExample
{publicstaticvoidmain（String[]args）{
Filef=newFile（"c:
\\large.txt"
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