java枚举（java枚举）

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1、java枚举（java枚举）TalkaboutusingenumerationsinJavaProgrammersmovingfromC++toJavaalwayshavealotofcomplaintsaboutJavaatfirst,withnoenumerationasamoreprominentproblem.Sowhydoesn'tJavasupportenumerations?Whatdoesitmeantosupportenumerationfromthepointofviewofprocedurallanguage?Canwefindawaytomeetther

2、equirementsofC++programmersforenumerations?Well,nowlet'sdiscusstheproblem.Enumerationtype(Enumerated,Types)Let'stakealookatthefollowingsmallprogram:Enum,Day,{SUNDAY,MONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY};Thisstatementprovidesauserfriendlymethodofvariabledefinitionthatenumeratesal

3、lpossiblevaluesofthisdatatype,i.e.,MondaythroughSunday.Asidefromthespecificprogramminglanguage,thecorefunctionalityofenumerationsshouldbe:Thetypeofsecurity(TypeSafety)Thecompactandeffectiveenumerationdefinition(Compact,EfficientDeclarationnumericalofEnumeratedValues)Theseamlessandotherpartso

4、ftheprogram(Seamlessintegrationwithotherinteractionlanguagefeatures)Theoperationofthehighefficiency(Runtimeefficiency)Nowlet'sdiscusseachofthesecharacteristicsonebyone.1.typesofsecurityTheenumerationdeclarationcreatesanewtype.Itisdifferentfromotherexistingtypes,includingprimitivetypes(intege

5、rs,floats,etc.)andotherenumeratedtypeswithinthescopeofthecurrentscope(Scope).Whenyouassignvaluestofunctions,integertypesandenumeratedtypesarenotinterchangeable(unlessyoudoexplicittypeconversions),thecompilerwillenforcethat.Forexample,definesuchafunctionwithanenumerationspecifiedabove:Publicv

6、oidfoo(Day);Ifyoucallthisfunctionwithintegers,thecompilerwillgiveyouthewrongone.Foo(4);//compilationerrorIfyoufollowthisstandard,thenPascal,Ada,andC++arestrictlysupportedenumerations,andtheClanguageisnot.2.compact,efficientenumerationnumericdefinitionTheprocedurefordefiningenumerationsshould

7、besimple.Forexample,inJava,wehavesuchadefinitionof"quasienumeration":PublicstaticfinalintSUNDAYpublicstaticfinalint=0;MONDAY=1;publicstaticfinalintTUESDAYpublicstaticfinalint=2;WEDNESDAY=3;publicstaticfinalintTHURSDAYpublicstaticfinalint=4;FRIDAY=5