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}

3.Tocompiletheprogram,enterthiscommandintotheDOSwindow:

C:

\SomeDir>

IamINFO.java

4.Thecompilerwillcreateafilecontaining.Thisfilewillbenamed.

5.Torunthebytecodes,enterthiscommandintotheDOSwindow:

IamINFO

ProgrammingExercises2（twohours）

ModifytheCarclassofthechapterbyaddingtwomethods:

booleangasHog（）

evaluatestotrueifthemilespergallonislowerthan15.0.

booleaneconomyCar（）

evaluatestotrueifthemilespergallonishigherthan30.0.

TheconstructorandthecalculateMPG（）methodremainunchanged.EachofthesenewmethodsshouldusethecalculateMPG（）togetthemilespergallon,notcalculateitthemselves.Anif-elsestatementpicksthecorrectbooleanreturnvalue.

Putuserinteractionbackintothemain（）methodmethodsotheuserentersvaluesforeachcar.Themain（）methodusestheseadditionalmethodstowriteamessagetotheuserifthecarisagashogoraneconomycar.

Youmightbetemptedtomakeoneofthesecommondesignerrors:

SavingmilespergalloninaninstancevariableoftheobjectalongwithstartMiles,endMiles,andgallons.

Thisalmostseemslogical,butisapoordesign.Don'

tkeepapermanentcopyofavaluethatcanbeeasilycalculatedfromdata.Thereasonforthisisthatitaddscomplexitytotheobject,butofferslittleadvantage.

Directlycalculatingmilespergalloninsideeachofthenewmethods.

Itisusuallybesttodoaparticularcalculationinonlymethod,andtouseitwheneverthecalculationisneeded.Nowifthereisabuginthecalculation,orthecalculationmustbemodified,thereisonlyoneplacetolook.

\>

javaMiles

Enterfirstreading:

10000

Entersecondreading:

10400

Entergallons:

10

Milespergallon:

40

EconomyCar!

intfirst;

//thenumberofintegerstoaddup

Stringline;

BufferedReaderstdin=newBufferedReader（

newInputStreamReader（System.in））;

//getthenumberofintegerstoaddup

line=stdin.readLine（）;

first=Integer.parseInt（line.trim（））;

importjava.io.*;

classCar

{

//instancevariables

intstartMiles;

//Statingodometerreading

intendMiles;

//Endingodometerreading

doublegallons;

//Gallonsofgasused

//constructor

Car（intfirst,intlast,doublegals）

{

startMiles=first;

endMiles=last;

gallons=gals;

//methods

doublecalculateMPG（）

return（endMiles-startMiles）/gallons;

classMilesPerGallon

publicstaticvoidmain（String[]args）

Carcar=newCar（32456,32810,10.6）;

System.out.println（"

Milespergallonis"

+car.calculateMPG（））;

ProgrammingExercises3（fourhours）

Part1ImmutableBox

ImplementaclassBoxsimilartotheclassinapreviousreviewexercise.ButthenewimplementationofBoxwillhavebetterencapsulation.HereisthedocumentationforBox:

classBox

Aclassthatimplementsacardboardbox.

Constructors

Box（doublewidth,doubleheight,doublelength）

Box（doubleside）

Methods

doublevolume（）

doublearea（）

Lookatthepreviousprogrammingexerciseformorediscussionandforcodewhicheasilycanbemodifiedforthisandthenexttwoexercises.

InthecurrentimplementationofBoxmakealltheinstancevariablesprivate.ThismeansthatonlymethodsofaBoxobjectcanseethatobject'

sdata.Theobjectwillbeimmutableiftherearenoaccessmethodsthatmakechangestothisdata.Animmutableobjectisonewhosedatadoesnotchange.YoumayrememberthatStringobjectsareimmutable---oncethecharactersoftheStringaresetwithaconstructortheyneverchange（althoughtheycanbeusedtocreateotherStringobjects.）Therearemanyadvantagestousingimmutableobjects,especiallywhenprogrammingwiththreads（whichishownearlyallbigprogramsarewritten.）

GivepublicaccesstothemethodsofBox.

TestyourBoxclasswithseveralversionsofthisprogram:

importBox;

classBoxTester

publicstaticvoidmain（String[]args）

Boxbox=newBox（2.5,5.0,6.0）;

Area:

"

+box.area（）+"

volume:

+box.volume（））;

length:

+box.length+"

height:

+box.height+

width:

+box.width）;

Part2:

PrivateMethodsforBox

Theimplementationofarea（）giveninthepreviousreviewexerciseisprobablyreasonablefortheBoxclass.Buttopracticeprivatemethodswriteitlikethis:

doublearea（）

return2*faceArea（）+2*topArea（）+2*sideArea（）;

Inthis,faceArea（）,topArea（）,andsideArea（）areprivatemethodsthatcalculatetheareaofthefrontface,thetopandthesideofthebox.Youwillhavetoaddthemtoyourclass.Oftenprivatemethodsare"

helping"

methodsthatthepublicmethodsuse,butarenottobeusedoutsidetheclass.Testyourprogramwithseveralversionsofthefollowing:

topArea:

+box.topArea（））;

（Theaboveprogramwillnotcompile,asexpected.）

Part3:

BoxConstructorandAccessMethods

AddanewconstructortotheBoxclass:

Box（BoxoldBox）

ThisconstructorcreatesanewBoxobjectwithidenticaldimensionsastheoldBoxobject.Ofcourse,theoldobjectisnotchanged.

Nowaddsomeaccessmethods.Anaccessmethodisamethodthatcanbeusedtoaccesstheprivatevariables（andothervariables）ofanobject:

publicdoublelength（）

publicdoubleheight（）

publicdoublewidth（）

Eachofthesemethodsmerelyreturnsthevalueofoneinstancevariable.Sincetheobjectisimmutable,therewillbenoaccessmethodsthataltertheinstancevariables.Testyouprogramwithmodificationsoftheprevioustestingclass.

Exercise4:

BiggerBoxes

Itwouldbenicetocreateaboxthatisbiggerthanagivenbox.Writethismethod:

publicBoxbiggerBox（BoxoldBox）

Thisisapublicmethodthatreturns（evalutesto）areferencetoanewBox.ThenewBoxwillbe25%largerineachdimensionthattheoldbox.Themethodwillhavetouseaconstructorinsideofittocreatethenewbox:

returnnewBox（1.25*oldBox.width（）,......）

Nowwriteamethodthatreturnsaboxthatis25%smallerineverydimensionthanagivenbox.Asusual,writeatestingprogramthatexercisesyourclass.

Part5:

NestingBoxes

Writeamethodthatevaluatestotrueorfalsedependingonwhetheroneboxcompletelyfitsinsideanother:

publicbooleannests（BoxoutsideBox,BoxinsideBox）

Thisispotentiallyadifficultmethod,sincetheinsideboxmayfitornotfitdependingonhowitisrotated.Tosimplifythemethod,writeitsothatitreturnstrueifthetwoboxesnestwithoutconsideringrotations（soheightiscomparedtoheight,lengthcomparedtolength,andsoon.）

Whattoturnin:

Ifthiswereanassignmentinaregularclassyoumightbeaskedtoturninthefollowing:

Neatlywrittendocumentationofthefinalversionofyourclass.

Writethedocumentationinthestylegivenatthetopofthispage,similarinstyletomostJavaclassdocumentation.

Shortcommentsdescribeeachmethodandconstructor.

Privateinstancevariablesandprivatemethodsarenotmentionedinthisdocumentation.Thedocumentationissupposedtodescribetheinterfacetousersoftheclass.

Thesourcecodeforthefinalimplementationoftheclass.

Commentsatthetopofthesoucedescribewhatitis,whowroteit,whenitwaswritten,andwhatisdebuggingstatusis.

Shortcommentsareusedtoexplaineachmethodandsomestatements.

Indentingandblanklinesmustbeusedtoshowthestructureandorganizationoftheclass.

Sourcecodeandoutputforseveralsmallprogramsthattestthevariousfeaturesoftheclass.

Often,puttingtogetherthematerialtoturninisasubstantialpartofthework.Thisisgoodpracticeforthe"

realworld."

classBox

//InstanceVariables

doublelength;

doublewidth;

doubleheight;

//Constructors

Box（doublewidth,doubleheight,doublelength）

this.width=width;

this.height=height;

this.length=length;

Box（doubleside）

width=side;

height=side;

length=side;

//Methods

doublevolume（）

returnwidth*height*length;

return2*（*+

*+

*）;

import;

//createaboxwithsides=2.5,3.0,and5.0

Boxbox1=newBox（2.5,3.0,5.0）;

Box1Area:

+box1.area（）+

Volume:

+box1.volume（））;

//createaboxwithallsides=3.0

Boxbox2=Box（）;

Box2Area:

+box2.area（）+

+box2.volume（））;

Part1UserInteraction.

ModifythePantryTesterclasssothatitcarriesoutadialogwiththeuser:

WelcometoMotherHubbard'

sPantry!

Thejamsare:

1:

Gooseberry7/4/8612fl.oz.

2:

CrabApple9/30/998fl.oz.

3:

Rhubarb10/31/9916fl.oz.

Enteryourselection（1,2,or3）:

1

Enteramounttospread:

2

Spreading2fluidouncesofGooseberry

Gooseberry7/4/8610fl.oz.