android学习格式安卓ndk的之旅

jni.bookPagePAGE1Thursday,February21,20024:36jni.bookPagePAGE1Thursday,February21,20024:36Linux公社)是包括Ubuntu,Fedora,SUSEIT资讯等Linux。 Linux公社)是包括Ubuntu,Fedora,SUSEIT资讯等Linux。 ShengADDISON-AnimprintofAddisonWesleyLongman,Reading,Massachusetts•Harlow,England•MenloPark,CaliforniaBerkeley,California•DonMills,Ontario•SydneyBonn•Amsterdam•Tokyo•MexicoCity901SanAntonioRoad,PaloAlto,CA94303USA.Allrights.SunMicrosystems,Inc.hasinlectualpropertyrightsrelatingtoimplementationsofthetechnologydescribedinthispublication.Inparticular,andwithoutlimitation,theseinlectualpropertyrightsmayincludeoneormoreU.S.patents,foreignpatents,orpendingapplications.Sun,SunMicrosystems,theSunlogo,andallSun,Java,Jini,andSolarisbasedtrademarksandlogosaretrademarksorregisteredtrademarksofSunMicrosystems,IheUnitedStatesandotherthroughX/Open,.SunMicrosystems,Inc.(SUN)herebygrantstoyouafullypaid,nonexclusive,nontransferable,perpetual,worldwidelimitedlicense(withouttherighttosublicense)underSUN’sinlectualpropertyrightsthatareessentialtopracticethisspecification.Thislicenseallowsandislimitedtothecreationanddistributionofcleanroomimplementationsofthisspecificationthat:(i)includea(ii)implementalltherequiredinterfacesandfunctionalityoftheJava™2tform,StandardEdition,asdefinedbySUN,withoutsubsettingorsupersetting;(iii)donotaddanyadditionalpackages,classes,orinterfacestothejava.*orjavax.*packagesortheirsubpackages;(iv)passalltestsuitesrelatingtothemostrecentpublishedversionofthespecificationoftheJava™2tform,StandardEdition,thatareavailablefromSUNsix(6)monthspriortoanybetareleaseofthecleanroomimplementationorupgradethereto;(v)donotderivefromSUNsourcecodeorbinarymaterials;(vi)donotincludeanySUNsourcecodeorbinarymaterialswithoutanappropriateandseparatelicensefromSUN.U.S.ERNMENTUSE:Thisspecificationrelatestocommercialitems,processes,orsoftware.Accordingly,usebytheUnitedStatesernmentissubjecttothesetermsandconditions,consistentwithFAR12.211and12.212.EXPRESSORIMPLIED,INCLUDING,BUTNOTLIMITEDTO,THEIMPLIEDWARRANTIESOFMERCHANTABILITY,FITNESSFORAPARTICULARPURPOSE,ORNON-INFRINGE-THISPUBLICATIONCOULDINCLUDETECHNICALINACCURACIESORTYPOGRAPHI-CALERRORS.CHANGESAREPERIODICALLYADDEDTOTHEINFORMATIONHEREIN;THESECHANGESWILLBEINCORPORATEDINNEWEDITIONSOFTHEPUBLICATION.SUNMICROSYSTEMS,INC.MAYMAKEIMPROVEMENTSAND/ORCHANGESINANYTECHNOLOGY,PRODUCT,ORPROGRAMDESCRIBEDINTHISPUBLICATIONATANYThepublisheroffersdiscountsonthisbookwhenorderedintyforspecialsales.Formoreinformation,pleasecontacttheCorporate,ernment,andSpecialSalesGroup,CEPUB,AddisonWesleyLongman,Inc.,OneJacobWay,Reading,Massachusetts01867.ISBN0-201-32577-123456789-Firstprinting,JuneTotheVMjni.bookPageviiThursday,February21,20024:36jni.bookPageviiThursday,February21,20024:36Linux公社)是包括Ubuntu,Fedora,SUSEIT资讯等Linux。 Linux公社)是包括Ubuntu,Fedora,SUSEIT资讯等Linux。 PartOne:Introductionand The tformandHost Roleofthe ImplicationsofUsingthe WhentoUsethe Evolutionofthe Example Getting DeclaretheNative Compile oWorld CreatetheNativeMethodHeader WritetheNativeMethod CompiletheCSourceandCreateaNative Runthe PartTwo:Programmer’sBasicTypes,Strings,and ASimpleNativeMethod..................................... CPrototypeforImplementingtheNativeMethod........... NativeMethodArguments............................. ofTypes................................... AccessingStrings........................................... ConvertingtoNativeStrings........................... ingNativeStringResources........................ ConstructingNewStrings............................. OtherJNIStringFunctions............................ NewJNIStringFunctionsinJava2SDKRelease1.2...jni.bookPagePAGE\*romanviiiThursday,February21,20024:36jni.bookPagePAGE\*romanviiiThursday,February21,20024:36Linux公社)是包括Ubuntu,Fedora,SUSEIT资讯等Linux。 Linux公社)是包括Ubuntu,Fedora,SUSEIT资讯等Linux。 SummaryofJNIString ChoosingamongtheString Accessing AccessingArraysin AccessingArraysofPrimitive SummaryofJNIPrimitiveArray ChoosingamongthePrimitiveArray AccessingArraysof Fieldsand Accessing ProcedureforAccessinganInstance Field AccessingStatic Calling CallingInstance FormingtheMethod CallingStatic CallingInstanceMethodsofa Invoking CachingFieldandMethod CachingatthePointof CachingintheDefiningClass’s ComparisonbetweentheTwoApproachestoCaching PerformanceofJNIFieldandMethod LocalandGlobal LocalandGlobal Local Global WeakGlobal Comparing ing ingLocal ManagingLocalReferencesinJava2SDKRelease ingGlobal RulesforManaging CachingandThrowingExceptionsinNative AUtility ProperException Checkingfor Handling ExceptionsinUtility TheInvocation CreatingtheJavaVirtual LinkingNativeApplicationswiththeJavaVirtual LinkingwithaKnownJavaVirtual LinkingwithUnknownJavaVirtual AttachingNative AdditionalJNI JNIand MonitorEntryand MonitorWaitand ObtainingaJNIEnvPointerinArbitrary MatchingtheThread WritingInternationalized CreatingjstringsfromNative TranslatingjstringstoNative RegisteringNative LoadandUnload TheJNI_OnLoad TheJNI_OnUnload Reflection JNIProgrammingin LeveragingExistingNative One-to-OneMap........................................Shared One-to-OneMapversusShared ImplementationofShared TheCPointer TheCMalloc TheCFunction Peer PeerClassesinthe ingNativeData BackpointerstoPeer Trapsand Error PassingInvalidArgumentstoJNI Confusingjclasswith Truncatingjboolean BoundariesbetweenJavaApplicationandNative ConfusingIDswith CachingFieldandMethod TerminatingUnicode ViolatingAccessControl RetainingVirtualMachine ExcessiveLocalReference UsingInvalidLocal UsingtheJNIEnvacross MismatchedThread PartThree:OverviewoftheJNI Design LoadingNative Class ClassLoadersandNative LocatingNative ATypeSafety UnloadingNative LinkingNative Calling TheJNIEnvInterface OrganizationoftheJNIEnvInterface BenefitsofanInterface Passing GlobalandLocal ImplementingLocal WeakGlobal Accessing AccessingPrimitive Fieldsand Errorsand NoCheckingforProgramming JavaVirtualMachine Asynchronous JNI PrimitiveandReference Primitive Reference Thejvalue FieldandMethod String UTF-8 Class Field Method xJNI SummaryoftheJNI Directly-ExportedInvocationInterface TheJavaVM FunctionsDefinedinNative TheJNIEnv SpecificationofJNI jni.bookPagexiiThursday,February21,20024:36jni.bookPagexiiThursday,February21,20024:36Linux公社)是包括Ubuntu,Fedora,SUSEIT资讯等Linux。 Linux公社)是包括Ubuntu,Fedora,SUSEIT资讯等Linux。 jni.bookPagePAGE\*romanxiiiThursday,February21,20024:36jni.bookPagePAGE\*romanxiiiThursday,February21,20024:36Linux公社)是包括Ubuntu,Fedora,SUSEIT资讯等Linux。 Linux公社)是包括Ubuntu,Fedora,SUSEIT资讯等Linux。 THISbookcoverstheJava™NativeInterface(JNI).Itwillbeusefultoyouifyouareinterestedinanyofthefollowing:integratingaJavaapplicationwithlegacycodewritteninlanguagessuchasCorC++incorporatingaJavavirtualmachineimplementationintoanexistingapplica-tionwritteninlanguagessuchasCorC++implementingaJavavirtualunderstandingthetechnicalissuesinlanguageinteroperability,inparticularhowtohandlefeaturessuchasgarbagecollectionandmultithreadingFirstandforemost,thebookiswrittenfordevelopers.YouwillfindeasystepstogetstartedwiththeJNI,informativediscussionsonvariousJNIfeatures,andhelpfultipsonhowtousetheJNIeffectively.TheJNIwasinitiallyreleasedinearly1997.ThebooksummarizestwoyearsofcollectiveexperiencegainedbyengineersatSunMicrosystemsaswellasthevastnumberofdevelopersintheJavatechnologycommunity.Second,thebookpresentsthedesignrationaleofvariousJNIfeatures.Notonlyisthisofinteresttotheacademiccommunity,butathoroughunderstandingofthedesignisalsoaprerequisitetousingtheJNIeffectively.Third,apartofthebookisthedefinitiveJNIspecificationfortheJava2t-form.JNIprogrammersmayusethespecificationasareferencemanual.Javavir-tualmachineimplementorsmustfollowthespecificationtoachieveconformance.SendcommentsonthisspecificationorquestionsaboutJNItoourelectronicmailaddress: .ForthelatestontheJava2tform,ortogetthelatestJava2SDKrelease,visitourwebsiteath .ForupdatedinformationaboutTheJava™Series,includingerrataforthisbook,previews ingbooks,visit TheJNIwasdesignedfollowingaseriesofdiscussionsbetweenSunMicro-systemsandJavatechnologylicensees.TheJNIpartlyevolvedfromNetscape’sJavaRuntimeInterface(JRI),whichwasdesignedbyWarrenHarris.ManyfromJavatechnologylicenseecompaniesactivelyparticipatedinthedesigndis-cussions.TheyincludeRussArun(),PatrickBeard(Apple),SimonNash(IBM),KenRoot(In),IanEllison-Taylor(),andMikeTou-tonghi().TheJNIdesignalsobenefitedgreatlyfromSuninternaldesignreviewscon-ductedbyDaveBowen,JamesGosling,PeterKessler,TimLindholm,MarkRein-hold,DerekWhite,andFrankYellin.DaveBrown,DaveConnelly,JamesMcIlree,BenjaminRenaud,andTomRodriguezmadesignificantcontributionstotheJNIenhancementsinJava2SDK1.2.CarlaSchroer’steamofcompatibilitytestersinNovosibirsk,Russia,wrotecompatibilitytestsfortheJNI.Intheprocesstheyuncoveredceswheretheoriginalspecificationwasunclearor TheJNItechnologywouldnothavebeendevelopedanddeployedwithoutthemanagementsupportofDaveBowen,LarryAbrahams,DickNeiss, gaard,andAlanBaratz.IreceivedfullsupportandencouragementtoworkonthisbookfrommymanagerDaveTimLindholm,authorofTheJava™VirtualMachineSpecification,ledtheJavavirtualmachinedevelopmenteffortatthetimewhentheJNIwasbeingdesigned.Timdidpioneeringworkonthevirtualmachineandnativeinterfaces,advocatedtheuseoftheJNI,andaddedrigorandclaritytothisbook.Healsopro-videdtheinitialsketchforthisbook’s“kitchenanddiningroom”coverartdesign.Thisbookbenefitedfromthehelpofmanycolleagues.AnandPalaniswamywroteaportionofChapter10oncommontrapsandpitfalls.JanetKoenigcare-fullyreviewedapreliminarydraftandcontributedmanyusefulideas.StearnswroteadraftofChapter2basedontheonlineJNIIreceivedvaluablecommentsonadraftofthisbookfromCraigJ.Bordelon,MichaelBrundage,MaryDageforde,JoshuaEngel,andElliottHughes.LisaFriendly,editorofTheJava™Series,wasinstrumentalingettingthisbookwrittenandpublished.KenArnold,authorofTheJava™ProgrammingLanguage,firstsuggestedthataJNIbookbewritten.IamindebtedtoMikeHen-driksonandMarinaLangatAddison-Wesleyfortheirhelpandtheirpatiencethroughouttheprocess.Dianedoversawtheproductionprocessfromcopyeditingtofinalprinting.InthepastseveralyearsIhavehadtheprivilegeofworkingwithagroupoftalentedanddedicatedpeopleinJavaSoftwareatSunMicrosystems,inparticularmembersoftheoriginal,HotSpot,andSunLabsvirtualmachineteams.Thisbookisdedicatedtothem.ShengLiangMay1999jni.bookPagePAGE100Thursday,February21,20024:36jni.bookPagePAGE100Thursday,February21,20024:36Linux公社)是包括Ubuntu,Fedora,SUSEIT资讯等Linux。 Linux公社)是包括Ubuntu,Fedora,SUSEIT资讯等Linux。 PartOne:IntroductionandCHAPTERTHEJava™NativeInterface(JNI)isapowerfulfeatureoftheJavatform.ApplicationsthatusetheJNIcanincorporatenativecodewritteninprogramminglanguagessuchasCandC++,aswellascodewrittenintheJavalanguage.TheJNIallowsprogrammerstotakeadvantageofthepoweroftheJavatform,withouthavingtoabandontheirinvestmentsinlegacycode.BecausetheJNIisapartoftheJavatform,programmerscanaddressinteroperabilityissuesonce,andexpecttheirsolutiontoworkwithallimplementationsoftheJavat-ThisbookisbothaprogrammingguideandareferencemanualfortheJNI.Thebookconsistsofthreeparts:Chapter2introducestheJNIthroughasimpleexample.ItisatutorialintendedforthebeginninguserswhoareunfamiliarwiththeJNI.Chapters3to10constituteaprogrammer’sguidethatgivesabroadoverviewofanumberofJNIfeatures.Wewillgothoughaseriesofshortbutdescrip-tiveexamplestohighlightvariousJNIfeaturesandtopresentthetechniquesthathaveproventobeusefulinJNIprogramming.Chapters11to13presentthedefinitivespecificationforallJNItypesandfunctions.Thesechaptersarealsoorganizedtoserveasareferencemanual.ThisbooktriestoappealtoawideaudiencewithdifferentneedsfortheJNI.Thetutorialandprogrammingguidearetargetedtowardbeginningprogrammers,whereasexperienceddevelopersandJNIimplementorsmayfindthereferencesectionsmoreuseful.ThemajorityofreaderswilllikelybedeveloperswhousetheJNItowriteapplications.Theterm“you”inthisbookwillimplicitlydenotedeveloperswhoprogramwiththeJNI,asopposedtoJNIimplementorsorend-usersofapplicationswrittenusingtheJNI.ThebookassumesthatyouhavebasicknowledgeoftheJava,C,andC++programminglanguages.Ifnot,youmayrefertooneofthemanyexcellentbooksthatareavailable:TheJava™ProgrammingLanguage,SecondEdition,byKenArnoldandJamesGosling(Addison-Wesley,1998),TheCProgrammingLan-guage,SecondEdition,byBrianKernighanandDennisRitchie(Prentice3The tformandHost 1988),andTheC++ProgrammingLanguage,ThirdEdition,byBjarneStrous-trup(Addison-Wesley,1997).Theremainderofthischapterintroducesthebackground,role,andevolutionoftheJNI.The tformandHostBecausethisbookcoversapplicationswrittenintheJavaprogramminglanguageaswellasinnative(C,C++,etc.)programminglanguages,letusfirstclarifytheexactscopeoftheprogrammingenvironmentsfortheselanguages.TheJavatformisaprogrammingenvironmentconsistingoftheJavavir-tualmachine(VM)andtheJavaApplicationProgrammingInterface(API).1JavaapplicationsarewrittenintheJavaprogramminglanguage,andcompiledintoamachine-independentbinaryclassformat.AclasscanbeexecutedonanyJavavirtualmachineimplementation.TheJavaAPIconsistsofasetofclasses.AnyimplementationoftheJavatformisguaranteedtosupporttheJavaprogramminglanguage,virtualmachine,andAPI.Thetermhostenvironmentrepresentsthehostoperatingsystem,asetofnativelibraries,andtheCPUinstructionset.NativeapplicationsarewritteninnativeprogramminglanguagessuchasCandC++,compiledintohost-specificbinarycode,andlinkedwithnativelibraries.Nativeapplicationsandnativelibrar-iesaretypicallydependentonaparticularhostenvironment.ACapplicationbuiltforoneoperatingsystem,forexample,typicallydoesnotworkonotheroperatingJavatformsarecommonlydeployedontopofahostenvironment.Forexample,theJavaRuntimeEnvironment(JRE)isaSunproductthatsupportstheJavatformonexistingoperatingsystemssuchasSolarisandWindows.TheJavatformoffersasetoffeaturesthatapplicationscanrelyonindependentoftheunderlyinghostenvironment.RoleoftheWhentheJavatformisdeployedontopofhostenvironments,itmay desirableornecessarytoallowJavaapplicationstoworkcloselywithnativecodewritteninotherlanguages.ProgrammershavebeguntoadopttheJavatformtobuildapplicationsthatweretraditionallywritteninCandC++.Becauseof1.Asusedherein,thephrases“Javavirtualmachine”or“JavaVM”meanavirtualmachinefortheJavatform.Similarly,thephrase“JavaAPI”meanstheAPIfortheJavatform.4 Roleofthe existinginvestmentinlegacycode,however,JavaapplicationswillcoexistwithCandC++codeformanyyearstocome.TheJNIisapowerfulfeaturethatallowsyoutotakeadvantageoftheJavatform,butstillutilizecodewritteninotherlanguages.AsapartoftheJavavir-tualmachineimplementation,theJNIisatwo-wayinterfacethatallowsJavaapplicationstoinvokenativecodeandviceversa.Figure1.1illustratestheroleoftheJNI.andlibraryJavavirtualmachine andlibraryJavavirtualmachine andlibraryHostFigure1.1RoleoftheTheJNIisdesignedtohandlesituationswhereyouneedtocombineJavaapplicationswithnativecode.Asatwo-wayinterface,theJNIcansupporttwotypesofnativecode:nativelibrariesandnativeapplications.YoucanusetheJNItowritenativemethodsthatallowJavaapplicationstocallfunctionsimplementedinnativelibraries.JavaapplicationscallnativemethodsinthesamewaythattheycallmethodsimplementedintheJavapro-gramminglanguage.Behindthescenes,however,nativemethodsareimple-mentedinanotherlanguageandresideinnativelibraries.TheJNIsupportsaninvocationinterfacethatallowsyoutoembedaJavavir-tualmachineimplementationintonativeapplications.NativeapplicationscanlinkwithanativelibrarythatimplementstheJavavirtualmachine,andthenusetheinvocationinterfacetoexecutesoftwarecomponentswrittenintheJavaprogramminglanguage.Forexample,awebbrowserwritteninCcanexecutedownloadedappletsinanembeddedJavavirtualmachineimplemen-5ImplicationsofUsingthe ImplicationsofUsingtheRememberthatonceanapplicationusestheJNI,itriskslosingtwobenefitsoftheJavatform.First,JavaapplicationsthatdependontheJNIcannolongerreadilyrunonmultiplehostenvironments.EventhoughthepartofanapplicationwrittenintheJavaprogramminglanguageisportabletomultiplehostenvironments,itwillbenecessaryto pilethepartoftheapplicationwritteninnativeprogrammingSecond,whiletheJavaprogramminglanguageistype-safeandsecure,nativelanguagessuchasCorC++arenot.Asaresult,youmustuseextracarewhenwritingapplicationsusingtheJNI.Amisbehavingnativemethodcancorrupttheentireapplication.ForthisreasonJavaapplicationsaresubjecttosecuritychecksbeforeinvokingJNIfeatures.Asageneralrule,youshouldarchitecttheapplicationsothatnativemethodsaredefinedinasfewclassesaspossible.Thisentailsacleanerisolationbetweennativecodeandtherestoftheapplication.WhentoUsetheBeforeyouembarkonaprojectusingtheJNI,itisworthtakingastepbacktoinvestigatewhethertherearealternativesolutionsthataremoreappropriate.Asmentionedinthelastsection,applicationsthatusetheJNIhaveinherentdisadvan-tageswhencomparedwithapplicationswrittenstrictlyintheJavaprogramminglanguage.Forexample,youlosethetype-safetyguaranteeoftheJavaprogram-minglanguage.AnumberofalternativeapproachesalsoallowJavaapplicationstointeroper-atewithcodewritteninotherlanguages.Forexample:AJavaapplicationmaycommunicatewithanativeapplicationthroughaTCP/IPconnectionorthroughotherinter-processcommunication(IPC)AJavaapplicationmayconnecttoalegacydatabasethroughtheJDBC™AJavaapplicationmaytakeadvantageofdistributedobjectsuchastheJavaIDLAPI.AcommoncharacteristicofthesealternativesolutionsisthattheJavaapplica-tionandnativecoderesideindifferentprocesses(andinsomecasesondifferentmachines).Processseparationoffersanimportantbenefit.Theaddressspace6 Evolutionofthe tectionsupportedbyprocessesenablesahighdegreeoffaultisolation—acrashednativeapplicationdoesnotimmediayterminatetheJavaapplicationwithwhichitcommunicatesoverTCP/IP.Sometimes,however,youmayfinditnecessaryforaJavaapplicationtocom-municatewithnativecodethatresidesinthesameprocess.Thisiswhentheesuseful.Consider,forexample,thefollowingTheJavaAPImightnotsupportcertainhost-dependentfeaturesneededbyanapplication.Anapplicationmaywanttoperform,forexample,specialfileoperationsthatarenotsupportedbytheJavaAPI,yetitisbothcumbersomeandinefficienttomanipulatefilesthroughanotherprocess.Youmaywanttoaccessanexistingnativelibraryandarenotwillingtopayfortheoverheadofcopyingandtransmittingdataacrossdifferentprocesses.Loadingthenativelibraryinthesameprocessismuchmoreefficient.Havinganapplicationspanmultipleprocessescouldresultinunacceptablememoryfootprint.Thisistypicallytrueiftheseprocessesneedtoresideonthesame machine.Loadinganativelibraryintotheexistingprocesshostingtheapplicationrequireslesssystemresourcesthanstartinganewpro-cessandloadingthelibraryintothatprocess.Youmaywanttoimplementasmallportionoftime-criticalcodeinalower-levellanguage,suchasassembly.Ifa3D-intensiveapplicationspendsmostofitstimeingraphicsrendering,youmayfinditnecessarytowritethecorepor-tionofagraphicslibraryinassemblycodetoachieve umperformance.Insummary,usetheJNIifyourJavaapplicationmustinteroperatewithnativecodethatresidesinthesameprocess.EvolutionoftheTheneedforJavaapplicationstointeroperatewithnativecodehasbeenrecog-nizedsincetheveryearlydaysoftheJavatform.ThefirstreleaseoftheJavatform,JavaDevelopmentKit(JDK™)release1.0,includedanativemethodinterfacethatallowedJavaapplicationstocallfunctionswritteninotherlan-guagessuchasCandC++.Manythird-partyapplications,aswellastheimple-mentationoftheJavaclasslibraries(including,forexample,java.lang,java.io,and),reliedonthenativemethodinterfacetoaccessthefea-turesintheunderlyinghostenvironment.Unfortunay,thenativemethodinterfaceinJDKrelease1.0hadtwomajor7Example First,thenativecodeaccessesfieldsinobjectsasmembersofCstructures.However,theJavavirtualmachinespecificationdoesnotdefinehowobjectsarelaidoutinmemory.IfagivenJavavirtualmachineimplementationlaysoutobjectsinawayotherthanthatassumedbythenativemethodinterface,thenyouhaveto pilethenativemethodlibraries.Second,thenativemethodinterfaceinJDKrelease1.0reliesonaconserva-tivegarbagecollectorbecausenativemethodscangetholdofdirectpointerstoobjectsinthevirtualmachine.AnyvirtualmachineimplementationthatusesmoreadvancedgarbagecollectionalgorithmscannotsupportthenativemethodinterfaceinJDKrelease1.0.TheJNIwasdesignedto etheseproblems.ItisaninterfacethatcanbesupportedbyallJavavirtualmachineimplementationsonawidevarietyofhostenvironments.WiththeJNI:EachvirtualmachineimplementorcansupportalargerbodyofnativeDevelopmenttoolvendorsdonothavetodealwithdifferentkindsofnativemethodinterfaces.Mostimportantly,applicationprogrammersareabletowriteoneversionoftheirnativecodeandthisversionwillrunondifferentimplementationsoftheJavavirtualmachine.TheJNIwasfirstsupportedinJDKrelease1.1.Internally,however,JDKrelease1.1stillusesold-stylenativemethods(asinJDKrelease1.0)toimplementtheJavaAPIs.ThisisnolongerthecaseinJava2SDKrelease1.2(formerlyknownasJDKrelease1.2).Nativemethodshavebeenrewrittensothattheycon-formtotheJNIstandard.TheJNIisthenativeinterfacesupportedbyallJavavirtualmachineimple-mentati