软件外文翻译.docx

软件外文翻译.docx

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软件外文翻译

学校代码：

10128

学号：

201130205034

本科毕业设计外文文献翻译

（

英文题目：

Java2MicroEditionandtheWorldofJava

题目：

J2ME和Java领域

学生姓名：

李晓燕

学院：

信息工程学院

系别：

软件工程系

专业：

软件工程

班级：

软件11-4

指导教师：

王慧讲师

企业导师：

郝传政工程师

二〇一五年五月

Java2MicroEditionandtheWorldofJava

1.Introduction

Thecomputerrevolutionofthe1970sincreasedthedemandforsophisticatedcomputersoftwaretotakeadvantageoftheever-increasingcapacityofcomputerstoprocessdata.TheCprogramminglanguagebecamethelinchpinthatenabledprogrammerstobuildsoftwarethatwasjustasrobustasthecomputeritranon.

Asthe1980sapproached,programmerswerewitnessinganotherspurtintheevolutionofprogramminglanguage.ComputertechnologyadvancedbeyondthecapabilitiesoftheCprogramminglanguage.Theproblemwasn’tnew.Itoccurredpreviouslyandcausedthedemiseofgenerationsofprogramminglanguages.Theproblemwasthatprogramswerebecomingtoocomplicatedtodesign,write,andmanagetokeepupwiththecapabilitiesofcomputers.ItwasaroundthistimethatadesignconceptbasedonSimula67andSmalltalk（fromthelate1960s）movedprogrammingtothenextevolutionarystep.Thiswastheperiodwhenobject-orientedprogramming（OOP）,andwithitanewprogramminglanguagecalledC++,tookprogrammersbystorm.

In1979,BjarneStroustrupofBellLaboratoriesinNewJerseyenhancedtheCprogramminglanguagetoincludeobject-orientedfeatures.HecalledthelanguageC++.（The++istheincrementaloperatorintheCprogramminglanguage.）C++istrulyanenhancementoftheCprogramminglanguage,anditbeganasapreprocessorlanguagethatwastranslatedintoCsyntaxbeforetheprogramwasprocessedbythecompiler.

Stroustrupbuiltontheconceptofaclass（takenfromSimula67andSmalltalk）,fromwhichinstancesofobjectsarecreated.Aclasscontainsdatamembersandmemberfunctionsthatdefineanobject’sdataandfunctionality.Healsointroducedtheconceptofinheritance,whichenabledaclasstoinheritsomeoralldatamembersandmemberfunctionsfromoneormoreotherclasses—allofwhichcomplementstheconceptsofobject-orientedprogramming.By1988,ANSIofficialsstandardizedStroustrup’sC++specification.

2.EnterJava

JustasC++wasbecomingthelanguageofchoiceforbuildingindustrial-strengthapplications,anothergrowthspurtintheevolutionofprogramminglanguagewasbudding,fertilizedbythelatestdisruptivetechnology—theWorldWideWeb.TheInternethadbeenawell-keptsecretfordecadesbeforetheNationalScienceFoundation（whooversawtheInternet）removedbarriersthatpreventedcommercialization.Until1991whenitwasopenedtocommerce,theInternetwasthealmostexclusivedomainofgovernmentagenciesandtheacademiccommunity.Oncethebarriertocommercializationwaslifted,theWorldWideWeb—oneofseveralservicesofferedontheInternet—becameavirtualcommunitycenterwherevisitorscouldgetfreeinformationaboutpracticallyanythingandbrowsethroughthousandsofvirtualstores.

BrowserspowertheWorldWideWeb.AbrowsertranslatesASCIItextfileswritteninHTMLintoaninteractivedisplaythatcanbeinterpretedonanymachine.AslongasthebrowseriscompatiblewiththecorrectversionofHTMLandHTTPimplementation,anycomputerrunningthebrowsercanusethesameHTMLdocumentwithouthavingtomodifyitforaparticulartypeofcomputer,whichwassomethingunheardofatthetime.ProgramswritteninCorC++aremachinedependentandcannotrunonadifferentachineunlesstheprogramisrecompiled.

TheccessoftheInternetgaverenewedfocustodevelopingamachine-independentprogramminglanguage.AndthesameyeartheInternetwascommercialized,fivetechnologistsatSunMicrosystemssetouttodojustthat.JamesGosling,PatrickNaughton,ChrisWarth,EdFrank,andMikeSheridanspent18monthsdevelopingtheprogramminglanguagetheycalledOak,whichwasrenamedJavawhenthisnewlanguagemadeitsdebutin1995.Javawentthroughnumerousiterationsbetween1991and1995,duringwhichtimemanyothertechnologistsatSunmadesubstantialcontributionstothelanguage.TheseincludedBillJoy,ArthurvanHoff,JonathanPayne,FrankYelin,andTimLindholm.

AlthoughJavaiscloselyassociatedwiththeInternet,itwasdevelopedasalanguageforprogrammingsoftwarethatcouldbeembeddedintoelectronicdevicesregardlessofthetypeofCPUusedbythedevice.ThisisknownastheEmbeddedJavaplatformandisincontinuoususetodayforclosedsystems.

TheJavateamfromSunsucceededincreatingaportableprogramminglanguage,somethingthathadeludedprogrammerssincecomputerswerefirstprogrammed.Theirsuccess,however,wasfarbeyondtheirwildestdreams.ThesameconceptusedtomakeJavaprogramsportabletoelectronicdevicesalsocouldbeusedtomakeJavaprogramsrunoncomputersrunningMicrosoftWindows,UNIX,andMacintosh.Timingwasperfect.TheInternet/intranethadwhettedcorporateAmerica’sappetiteforcost-effective,portableprogramsthatcouldreplacemission-criticalapplicationswithinthecorporation.AndJavahadprovenitselfasaprogramminglanguageusedtosuccessfullydevelopmachine-independentapplications.

3.JavaVirtualMachine

WritingJavaprogramsissimilartowritingC++programsinthattheprogrammerwritessourcecodethatcontainsinstructionsintoaneditor,orinanintegrateddevelopmentenvironment,andthenthesourcecodeiscompiled.However,that’swhereJavaandC++partways.ThecompilingandlinkingprocessofaC++programresultsinanexecutablethatcanberunonanappropriatemachine.Incontrast,theJavacompilerconvertsJavasourcecodeintobytecodethatisexecutedbytheJavaVirtualMachine（JVM）.

Machine-specificinstructionsarenotincludedinbytecode.Instead,theyalreadyresideintheJVM,whichismachinespecific.ThismeansthatthebytecodemightcontainfewerinstructionsthatneedtobetranslatedthanacomparableC++program.

AlthoughtheJavacompilergeneratesbytecodethatmustbeinterpretedbytheJVMatruntime,thenumberofinstructionsthatneedtranslationareusuallyminimalandhavealreadybeenoptimizedbytheJavacompiler.

4.BacktotheFuture:

J2ME

RememberthatJavabeganasaprogramminglanguagetocreateprogramsforembeddedsystems—microcomputersfoundinconsumerandindustrialproductssuchasthoseusedtocontrolautomobilesandappliances.ThedevelopmentteamatSunworkedonJavaintheearly1990stoaddresstheprogrammingneedsofthefledglingembeddedcomputermarket,butthateffortwassidetrackedbymorecompellingopportunitiespresentedbytheInternet.

Asthoseopportunitieswereaddressed,anewbreedofportablecommunicationsdevicesopenedotheropportunitiesattheturnofthecentury.CellphonesexpandedJ2ME:

TheCompleteReferencefromvoicecommunicationsdevicestovoiceandtextcommunicationsdevices.Pocketelectronictelephonedirectoriesevolvedintopersonaldigitalassistants.Chipmakerswerereleasingnewproductsatthistimethatweredesignedtotransfercomputingpowerfromadesktopcomputerintomobilesmallcomputersthatcontrolledgaspumps,cabletelevisionboxes,andanassortmentofotherappliances.

ThetimewasrightforthenextevolutionofJava.However,insteadofbeefingupJavawithadditionalAPIs,theteamatSun,alongwiththeJavaCommunityProcessProgram,dismantledboththeJavaprogramminglanguageandtheJavaVirtualMachine.TheystrippeddownJavaAPIsandtheJVMtotheminimumcodingrequiredtoprovideintelligencetoembeddedsystemsandmicrocomputerdevices.Thiswasnecessarybecauseofresourceconstraintsimposeduponthehardwaredesignofthesedevices.TheresultoftheireffortsisJ2ME.J2MEisareducedversionoftheJavaAPIandJavaVirtualMachinethatisdesignedtooperatewithinthesparseresourcesavailableinthenewbreedofembeddedcomputersandmicrocomputers.

5.HowJ2MEIsOrganized

Traditionalcomputingdevicesusefairlystandardhardwareconfigurationssuchasadisplay,keyboard,mouse,andlargeamountsofmemoryandpermanentstorage.However,thenewbreedofcomputingdeviceslackshardwareconfigurationcontinuityamongdevices.Somedevicesdon’thaveadisplay,permanentstorage,keyboard,ormouse.Andmemoryavailabilityisinconsistentamongsmallcomputingdevices.ThelackofuniformhardwareconfigurationamongthesmallcomputingdevicesposesaformidablechallengefortheJavaCommunityProcessProgram,whichischargedwithdevelopingstandardsfortheJVMandtheJ2MEforsmallcomputingdevices.

J2MEmustservicemanydifferentkindsofsmallcomputingdevices,includingscreenphones,digitalset-topboxesusedforcabletelevision,cellphones,andpersonaldigitalassistants.ThechallengefortheJavaCommunityProcessProgramistodevelopaJavastandardthatcanbeimplementedonsmallcomputingdevicesthathavenonstandardhardwareconfigurations.TheJavaCommunityProcessProgramhasusedatwofoldapproachtoaddressingtheneedsofsmallcomputingdevices.First,theydefinedtheJavarun-timeenvironmentandcoreclassesthatoperateoneachdevice.Thisisreferredtoastheconfiguration.AconfigurationdefinestheJavaVirtualMachineforaparticularsmallcomputingdevice.Therearetwoconfigurations,oneforhandhelddevicesandtheotherforplug-indevices.Next,theJavaCommunityProcessProgramdefinedaprofileforcategoriesofsmallcomputingdevices.Aprofileconsistsofclassesthatenabledeveloperstoimplementfeaturesfoundonarelatedgroupofsmallcomputingdevices.

6.J2MEconfigurations

TherearetwoconfigurationsforJ2MEasofthiswriting.TheseareConnectedLimitedDeviceConfiguration（CLDC）andtheConnectedDevice