01Everything is an Object.docx

01Everything is an Object.docx

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01EverythingisanObject

EverythingisanObject

TosatisfyIDEslikeEclipse,wehaveincludedpackagestatementsforchapters

beforeAccessControl.Ifyouhavesolvedtheproblemsinthischapterwithout

usingpackagestatements,yoursolutionsarestillcorrect.

Exercise1

//:

object/E01_DefaultInitialization.java

/******************Exercise1*****************

*Createaclasscontaininganintandachar

*thatarenotinitialized.Printtheirvalues

*toverifythatJavaperformsdefault

*initialization.

***********************************************/

packageobject;

publicclassE01_DefaultInitialization{

inti;

charc;

publicE01_DefaultInitialization（）{

System.out.println（"i="+i）;

System.out.println（"c=["+c+']'）;

}

publicstaticvoidmain（String[]args）{

newE01_DefaultInitialization（）;

}

}/*Output:

i=0

c=[]

*///:

~

Whenyouruntheprogramyou’llseethatbothvariablesaregivendefault

values:

0fortheint,anda“space”forthechar.

Exercise2

//:

object/E02_HelloWorld.java

10ThinkinginJava,4thEditionAnnotatedSolutionGuide

/******************Exercise2******************

*FollowtheHelloDate.javaexampleinthis

*chaptertocreatea"hello,world"programthat

*simplydisplaysthatstatement.Youneedonlya

*singlemethodinyourclass（the"main"onethat

*executeswhentheprogramstarts）.Remember

*tomakeitstaticandtoincludetheargument

*list（eventhoughyoudon'tuseit）.

*Compiletheprogramwithjavacandrunitusing

*java.Ifyouareusingadifferentdevelopment

*environmentthantheJDK,learnhowtocompile

*andrunprogramsinthatenvironment.

************************************************/

packageobject;

publicclassE02_HelloWorld{

publicstaticvoidmain（String[]args）{

System.out.println（"Hello,world!

"）;

}

}/*Output:

Hello,world!

*///:

~

Exercise3

//:

object/E03_ATypeName.java

/******************Exercise3******************

*TurnthecodefragmentsinvolvingATypeName

*intoaprogramthatcompilesand

*runs.

************************************************/

packageobject;

publicclassE03_ATypeName{

publicstaticvoidmain（String[]args）{

E03_ATypeNamea=newE03_ATypeName（）;

}

}///:

~

Exercise4

//:

object/E04_DataOnly.java

/******************Exercise4******************

*TurntheDataOnlycodefragmentsintoa

*programthatcompilesandruns.

EverythingisanObject11

************************************************/

packageobject;

publicclassE04_DataOnly{

inti;

doubled;

booleanb;

publicstaticvoidmain（String[]args）{

E04_DataOnlyd=newE04_DataOnly（）;

d.i=47;

d.d=1.1;

d.b=false;

}

}///:

~

Exercise5

//:

object/E05_DataOnly2.java

/******************Exercise5******************

*ModifyExercise4sothevalues

*ofthedatainDataOnlyareassignedtoand

*printedinmain（）.

************************************************/

packageobject;

publicclassE05_DataOnly2{

publicstaticvoidmain（String[]args）{

E04_DataOnlyd=newE04_DataOnly（）;

d.i=47;

System.out.println（"d.i="+d.i）;

d.d=1.1;

System.out.println（"d.d="+d.d）;

d.b=false;

System.out.println（"d.b="+d.b）;

}

}/*Output:

d.i=47

d.d=1.1

d.b=false

*///:

~

Exercise6

//:

object/E06_Storage.java

/******************Exercise6******************

12ThinkinginJava,4thEditionAnnotatedSolutionGuide

*Writeaprogramthatincludesandcallsthe

*storage（）methoddefinedasacodefragmentin

*thischapter.

************************************************/

packageobject;

publicclassE06_Storage{

Strings="Hello,World!

";

intstorage（Strings）{

returns.length（）*2;

}

voidprint（）{

System.out.println（"storage（s）="+storage（s））;

}

publicstaticvoidmain（String[]args）{

E06_Storagest=newE06_Storage（）;

st.print（）;

}

}/*Output:

storage（s）=26

*///:

~

Exercise7

//:

object/E07_Incrementable.java

/******************Exercise7******************

*TurntheIncrementablecodefragmentsintoa

*workingprogram.

************************************************/

packageobject;

classStaticTest{

staticinti=47;

}

publicclassE07_Incrementable{

staticvoidincrement（）{StaticTest.i++;}

publicstaticvoidmain（String[]args）{

E07_Incrementablesf=newE07_Incrementable（）;

sf.increment（）;

E07_Incrementable.increment（）;

increment（）;

}

}///:

~

EverythingisanObject13

Youcancallincrement（）byitself,becauseastaticmethod（main（）,inthis

case）cancallanotherstaticmethodwithoutqualification.

Exercise8

//:

object/E08_StaticTest.java

/******************Exercise8******************

*Writeaprogramtodemonstratethatno

*matterhowmanyobjectsyoucreateofa

*particularclass,thereisonlyoneinstance

*ofaparticularstaticfieldinthatclass.

************************************************/

packageobject;

publicclassE08_StaticTest{

staticinti=47;

publicstaticvoidmain（String[]args）{

E08_StaticTestst1=newE08_StaticTest（）;

E08_StaticTestst2=newE08_StaticTest（）;

System.out.println（st1.i+"=="+st2.i）;

st1.i++;

System.out.println（st1.i+"=="+st2.i）;

}

}/*Output:

47==47

48==48

*///:

~

TheoutputshowsthatbothinstancesofE08_StaticTestsharethesamestatic

field.Weincrementedthesharedfieldthroughthefirstinstanceandtheeffect

wasvisibleinthesecondinstance.

Exercise9

//:

object/E09_AutoboxingTest.java

/******************Exercise9******************

*Writeaprogramtodemonstratethat

*autoboxingworksforalltheprimitivetypes

*andtheirwrappers.

************************************************/

packageobject;

publicclassE09_AutoboxingTest{

publicstaticvoidmain（String[]args）{

14ThinkinginJava,4thEditionAnnotatedSolutionGuide

Byteby=1;

bytebt=by;

System.out.println（"byte="+bt）;

Shortsh=1;

shorts=sh;

System.out.println（"short="+s）;

Integerin=1;

inti=in;

System.out.println（"int="+i）;

Longlo=1L;

longl=lo;

System.out.println（"long="+l）;

Booleanbo=true;

booleanb=bo;

System.out.println（"boolean="+b）;

Characterch='x';

charc=ch;

System.out.println（"char="+c）;

Floatfl=1.0f;

floatf=fl;

System.out.println（"float="+f）;

Doubledb=1.0d;

doubled=db;

System.out.println（"double="+d）;

}

}/*Output:

byte=1

short=1

int=1

long=1

boolean=true

char=x

float=1.0

double=1.0

*///:

~

ThetermsAutoboxingandAutounboxingappearoftenintheliterature.The

onlydifferenceisthedirectionoftheconversion:

autoboxingconvertsfromthe

primitivetypetothewrapperobject,andautounboxingconvertsfromthe

wrappedtypetotheprimitivetype.

Exercise10

//:

object/E10_ShowArgs.java

//{Args:

ABC}

/******************Exercise10****************

EverythingisanObject15

*Writeaprogramthatprintsthreearguments

*takenfromthecommandline.

*You'llneedtoindexintothecommand-line

*arrayofStrings.

***********************************************/

packageobject;

publicclassE10_ShowArgs{

publicstaticvoidmain（String[]args）{

System.out.println（args[0]）;

System.out.println（args[1]）;

System.out.println（args[2]）;

}

}/*Output:

A

B

C

*///:

~

Remember,whenyouwanttogetanargumentfromthecommandline:

•ArgumentsareprovidedinaStringarray.

•args[0]isthefirstcommand-lineargumentandnotthenameofthe

program（asitisinC）.

•You’llcausearuntimeexceptionifyouruntheprogramwithoutenough

arguments.

Youcantestforthelengthofthecommand-lineargumentarraylikethis:

//:

object/E10_ShowArgs2.java

//{Args:

ABC}

packageobject;

publicclassE10_ShowArgs2{

publicstaticvoidmain（String[]args）{

if（args.length<3）{

System.err.println（"Need3arguments"）;

System.exit

（1）;

}

System.out.println（args[0]）;

System.out.println（args[1]）;

System.out.println（args[2]）;

}

}/*Output:

A

B

16ThinkinginJava,4thEditionAnnotatedSolutionGuide

C

*///:

~

System.exit（）terminatestheprogramandpassesitsargumentbacktothe

operatingsystemasastatuscode.（Withmostoperatingsystems,anon-zero

statuscodeindicatesthattheprogramexecutionfailed.）Typically,yousend

errormessagestoSystem.err,asshownabove.

Exercise11

//:

object/E11_AllTheColorsOfTheRainbow.java

/******************Exercise11*****************

*TurntheAllTheColorsOfTheRainbowexampleinto

*aprogramthatcompilesandruns.

************************************************/

packageobject;

publicclassE11_AllTheColorsOfTheRainbow{

intanIntegerRepresentingColors;

voidchangeTheHueOfTheColor（intnewHue）{

anIntegerRepresentingColors=newHue;

}

publicstaticvoidmain（String[]args）{

E11_AllTheColorsOfTheRainbowall=

newE11_AllTheColorsOfTheRainbow（）;

all.changeTheHueOfTheColor（27）;

}

}///:

~

Exercise12

//:

object/E12_LeftToReader.java

/******************Exercise12*****************

*Findthecodeforthesecondversionof

*HelloDate.java,thesimplecomment-

*documentationexample.ExecuteJavadoconthe

*fileandviewtheresultswithyourWebbrowser.

************************************************/

packageobject;

publicclassE12_LeftToReader{

publicstaticvoidmain（Stringargs[]）{

System.out.println（"Exerciselefttoreader"）;

}

}///:

~

EverythingisanObject17

NotethatJavadocdoesn’tautomaticallycreatethedestinationdirectory.

ConsulttheJavadocreferenceintheJDKdocumentationtolearnthemany

usesofJavadoc.

Exercise13

//:

object/E13_LeftToReader.java

/******************Exercise13*****************

*RunDocumentation1.java,Documentation2.java,

*andDocumentation3.javathroughJavadoc.Verify

*theresultingdocumentationwithyourWeb

*