寝室管理系统外文翻译

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1、PolymorphismPolymorphismisthethirdessentialfeatureofanobject-orientedprogramminglanguage,afterdataabstractionandinheritance.Itprovidesanotherdimensionofseparationofinterfacefromimplementation，todecouplewhatfromhow.Polymorphismallowsimprovedcodeorganizati

2、onandreadabilityaswellasthecreationofextensibleprogramsthatcanbe“grown”notonlyduringtheoriginalcreationoftheproject，butalsowhennewfeaturesaredesired.Encapsulationcreatesnewdatatypesbycombiningcharacteristicsandbehaviors.Implementationhidingseparatesthein

3、terfacefromtheimplementationbymakingthedetailsprivate.Thissortofmechanicalorganizationmakesreadysensetosomeonewithaproceduralprogrammingbackground.Butpolymorphismdealswithdecouplingintermsoftypes.Inthelastchapter,yousawhowinheritanceallowsthetreatmentofa

4、nobjectasitsowntypeoritsbasetype.Thisabilityiscriticalbecauseitallowsmanytypes(derivedfromthesamebasetype)tobetreatedasiftheywereonetype，andasinglepieceofcodetoworkonallthosedifferenttypesequally.Thepolymorphicmethodcallallowsonetypetoexpressitsdistincti

5、onfromanother，similartype,aslongasthey’rebothderivedfromthesamebasetype.Thisdistinctionisexpressedthroughdifferencesinbehaviorofthemethodsthatyoucancallthroughthebaseclass.You’lllearnaboutpolymorphism(alsocalleddynamicbindingorlatebindingorrun-timebindin

6、g)startingfromthebasics,withsimpleexamplesthatstripawayeverythingbutthepolymorphicbehavioroftheprogram.UpcastingrevisitedYousawhowanobjectcanbeusedasitsowntypeorasanobjectofitsbasetype.Takinganobjectreferenceandtreatingitasareferencetoitsbasetypeiscalled

7、upcastingbecauseofthewayinheritancetreesaredrawnwiththebaseclassatthetop.Whyshouldanyoneintentionallyforgetthetypeofanobject?Thisiswhathappenswhenyouupcast，anditseemslikeitcouldbemuchmorestraightforwardiftune()simplytakesaWindreferenceasitsargument.Thisb

8、ringsupanessentialpoint:Ifyoudidthat,you’dneedtowriteanewtune()foreverytypeofInstrumentinyoursystem.SupposewefollowthisreasoningandaddStringedandBrassinstruments:Thisworks，butthere’samajordrawback:youmustwritetype-specific