面向对象设计（object oriented design ）

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1、面向对象设计000（Objectorienteddesign000）Basicknowledge:Simpleprinciplesandapplicationsofexceptionhandlingmechanismsin1.C++orJava.WhentheJAVAprogramviolatesthesemanticrulesofJAVA,theJAVAvirtualmachinewillrepresenttheerrorasanexception.Violationofsemanticrulesincludes2cases.Oneisthebuilt-insemanticch

2、eckintheJAVAclasslibrary.Forexample,ifthearraysubscriptisoutofbounds,theIndexOutOfBoundsExceptionwillberaised;theNullPointerExceptionobjectwillberaisedwhenaccessingthenull.Inanothercase,JAVAallowsprogrammerstoextendthissemanticcheck,whereprogrammerscancreatetheirownexceptionsandfreelychoosewh

3、entoraiseanexceptionwiththethrowkeyword.Allexceptionsaresubclassesofjava.lang.Thowable.The2.JavainterfaceisthesameanddifferentfromthevirtualclassofC++.SinceJavadoesnotsupportmultipleinheritance,andthereisapossibilitythataclassorobjectwillusemethodsorattributesthatareinseveralclassesorobjects,

4、theexistingsingleinheritancemechanismcannotmeettherequirements.Theinterfaceismoreflexiblethaninheritancebecausetheinterfacedoesnothaveanyimplementationcode.Whenaclassimplementsaninterface,theclasstoimplementtheinterfacemethodsandpropertiesofallthepropertiesoftheinterface,andinthedefaultstatei

5、sbelowpublicstatic,allthewaytothedefaultispublic.aclasscanimplementmultipleinterfaces.3.advantagesandprinciplesofgarbagecollection.2recyclingmechanismsareconsidered.AremarkablefeatureofJavalanguageisintroducedintothegarbagecollectionmechanism,memorymanagementmakesc++programmersthemosttroubles

6、omeproblemitmakesJavaprogrammerssmoothlydoneoreasilysolved,atthetimeofwritingprogramsnolongerneedtoconsidermemorymanagement.Becauseofagarbagecollectionmechanism,objectsinJavanolongerhavescopeconcepts,andonlythereferenceoftheobjecthasscope".Garbagecollectioncaneffectivelypreventmemoryleaks,and

7、effectivelyusethememoryyoucanuse.Thegarbagecollectorisusuallyusedasthethreadtorunaseparatelowlevel,unpredictablesituationsontheheapofdeadornotusedforalongtimetheobjectisclearandrecovery,callingthegarbagecollectorprogrammerscannotbereal-timega