Thinking in Java第四版Acess部分答案.docx

Thinking in Java第四版Acess部分答案.docx

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ThinkinginJava第四版Acess部分答案

ThinkinginJava4thEdition习题答案

1.Access部分

（NO.1）//access/AccessTest.java

//TIJ4ChapterAccess,Exercise5,page227

/*Createaclasswithpublic,private,protectedandpackage-accessfieldsand

*methodmembers.Createanobjectofthisclassandseewhatkindofcompiler

*messagesyougetwhenyoutrytoaccessalltheclassmembers.Beawarethat

*classesinthesamedirectoryarepartofthe"default"package.

*/

/*insamedirectory:

*packageaccess;

*

*publicclassFourWays{

*inta=0;

*publicintb=1;

*protectedintc=2;

*privateintd=3;

*FourWays（）{System.out.println（"FourWays（）constructor"）;}

*voidshowa（）{System.out.println（a）;}

*publicvoidshowb（）{System.out.println（b）;}

*protectedvoidshowc（）{System.out.println（c）;}

*privatevoidshowd（）{System.out.println（d）;}

*}

*/

packageaccess;//runcommandjavaaccess.AccessTest

publicclassAccessTest{

publicstaticvoidmain（String[]args）{

FourWaysfw=newFourWays（）;

fw.showa（）;

fw.showb（）;

fw.showc（）;

fw.a=10;

fw.b=20;

fw.c=30;

fw.showa（）;

fw.showb（）;

fw.showc（）;

//!

fw.showd（）;//privateaccess,compilercan'ttouch

}

}

（NO.2）//access/Collision.java

//TIJ4ChapterAccess,Exercise2,page217

/*Takethecodefragmentsinthissectionandturnthemintoaprogramand

*verifythatcollisionsdooccur.

*/

importnet.mindview.simple.*;

importjava.util.*;

publicclassCollision{

publicstaticvoidmain（String[]args）{

//Vectorv=newVector（）;//ambiquouscollision

net.mindview.simple.Vectorv1=newnet.mindview.simple.Vector（）;

java.util.Vectorv2=newjava.util.Vector（）;

}

}

（NO.3）//access/ConnectionManager.java

//TIJ4ChapterAccess,Exercise8,page233

/*FollowingtheformoftheexampleLunch.java,createaclasscalled

*ConnectionManagerthatmanagesafixedarrayofConnectionobjects.Theclient

*programmermustnotbeabletoexplicitlycreateConnectionobjects,butcan

*onlygetthemviaastaticmethodinConnectionManager.WhenConnectionManager

*runsoutofobjects,itreturnsanullreference.Testtheclassesinmain（）.*/

packageaccess;

classConnection{

privatestaticintcount=0;

privateinti=0;

privateConnection（）{System.out.println（"Connection（）"）;}

//Allowcreationviastaticmethod:

staticConnectionmakeConnection（）{

count++;

returnnewConnection（）;

}

publicstaticinthowMany（）{returncount;}

publicStringtoString（）{

return（"Connection"+count）;

}

}

publicclassConnectionManager{

staticinthowManyLeft=3;

staticConnection[]ca=newConnection[3];

{

for（Connectionx:

ca）

x=Connection.makeConnection（）;

}

publicstaticConnectiongetConnection（）{

if（howManyLeft>0）

returnca[--howManyLeft];

else{

System.out.println（"Nomoreconnections"）;

returnnull;

}

}

publicstaticvoidmain（String[]args）{

ConnectionManagercm=newConnectionManager（）;

System.out.println（cm.howManyLeft）;

cm.getConnection（）;

System.out.println（howManyLeft）;

cm.getConnection（）;

System.out.println（howManyLeft）;

cm.getConnection（）;

System.out.println（cm.getConnection（））;

System.out.println（howManyLeft）;

}

}

（NO.4）//access/cookie2/CookieMonster.java

//TIJ4ChapterAccess,Exercise4,page227

//Showthatprotectedmethodshavepackageaccessbutarenotpublic.

/*IndirectoryCookie2:

*//access/cookie2/Cookie.java

*//Createsalibrary

*packageaccess.cookie2;

*

*publicclassCookie{

*publicCookie（）{

*System.out.println（"Cookiecontstructor"）;

*}

*protectedvoidbite（）{System.out.println（"bite"）;}

*}

*/

packageaccess.cookie2;

publicclassCookieMonster{

publicstaticvoidmain（String[]args）{

Cookiex=newCookie（）;

x.bite（）;//packageaccesstoprotectedmethod

}

}

（NO.5）//access/debug/Debug.java

//TIJ4ChapterAccess,Exercise3,page220

/*Createtwopackages:

debuganddebugoff,containinganidenticalclasswitha

*debug（）method.ThefirstversiondisplaysitsStringargumenttotheconsole,

*theseconddoesnothing.Useastaticimportlinetoimporttheclassintoatest

*program,anddemonstratetheconditionalcompilationeffect.

*/

/*Indirectoryaccess/debugoff:

*//access/debugoff/Debug.java

*packageaccess.debugoff;

*

*publicclassDebug{

*publicstaticvoiddebug（Strings）{}

*}

*/

packageaccess.debug;

publicclassDebug{

publicstaticvoiddebug（Strings）{

System.out.println（s）;

}

}

（NO.6）//TIJ4chapterAccess,Exercise9,page233

/*Createinaccess/localdirectoryinyourCLASSPATH:

*//access/local/PackagedClass.java

*packageaccess.local;

*

*classPackagedClass{

*publicPackagedClass（）{

*System.out.println（"Creatingapackagedclass"）;

*}

*}

*//Then,inanotherdirectrorycreatethefilebelowandexplainwhycompiler

*generateserror.WouldmakingForeignclasspartofaccess.localchangeanything?

*/

//access/foreign/Foreign.java

packageaccess.foreign;

importaccess.local.*;

publicclassForeign{

publicstaticvoidmain（String[]args）{

PackagedClasspc=newPackagedClass（）;

}

}

/*Compilererrorbecause:

PackagedClassinnotpublic,sonoaccessoutsideof

*package.MovingForeigntolocalwouldallowpackageaccesstoPackagedClass.

*/

（NO.7）//MakeWidget.java

//TIJ4ChapterAccess,Exercise7,page230

/*CreatethelibraryaccordingtothecodefragmentsdescribingaccessandWidget.

*CreateaWidgetinaclassthatisnotpartoftheaccesspackage.

*/

/*inaccesspackage:

*//access/Widget.java

*packageaccess;

*

*publicclassWidget{

*publicWidget（）{System.out.println（"Widget（）"）;}

*}

*/

importaccess.*;

publicclassMakeWidget{

publicstaticvoidmain（String[]args）{

Widgetw=newWidget（）;

}

}

（NO.8）//access/ProtectedData.java

//TIJ4ChapterAccess,Exercise6,page228

/*Createaclasswithprotecteddata.Createasecondclassinthesamefilewith

*amethodthatmanipulatestheprotecteddatainthefirstclass.

*/

classSomeData{

protectedinta=13;

}

classDataChanger{

staticvoidchange（SomeDatasd,inti）{sd.a=i;}

}

publicclassProtectedData{

publicstaticvoidmain（String[]args）{

SomeDatax=newSomeData（）;

System.out.println（x.a）;

DataChanger.change（x,99）;

System.out.println（x.a）;

}

}

（NO.9）//access/UnpackagedMyClass.java

//TIJ4ChapterAccess,Exercise1,page217

//Createaclassinapackage.Createaninstanceofyourclassoutsideofthatpackage.

/*Inanotherdirectory:

*//access/mypackage/MyPackagedClass.java

*

*packageaccess.mypackage;

*

*publicclassMyPackagedClass{

*publicMyPackagedClass（）{System.out.println（"MyPackagedClass（）"）;}

*}

*/

publicclassUnpackagedMyClass{

publicstaticvoidmain（String[]args）{

access.mypackage.MyPackagedClassm=newaccess.mypackage.MyPackagedClass（）;

}

}

//arrays/ArrayOfGenerics10.java

//TIJ4ChapterArrays,Exercise10,page762

//ModifyArrayOfGeneric.javatousecontainersinsteadofarrays.

//Showthatyoucaneliminatethecompile-timewarnings.

importjava.util.*;

publicclassArrayOfGenerics10{

@SuppressWarnings（"unchecked"）

publicstaticvoidmain（String[]args）{

List>lls=newArrayList>（）;

Listl=newArrayList（）;

//lls=（List>）l;//error:

inconvertibletypes

lls.add（newArrayList（））;

List