Java外文翻译programminglanguage.docx

Java外文翻译programminglanguage.docx

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Java外文翻译programminglanguage

Java（programminglanguage）

FromWikipedia，thefreeencyclopedia

JavaisaprogramminglanguageoriginallydevelopedbyJamesGoslingatSunMicrosystems（whichhassincemergedintoOracleCorporation）andreleasedin1995asacorecomponentofSunMicrosystems'Javaplatform.ThelanguagederivesmuchofitssyntaxfromCandC++buthasasimplerobjectmodelandfewerlow—levelfacilities.Javaapplicationsaretypicallycompiledtobytecode（classfile）thatcanrunonanyJavaVirtualMachine（JVM）regardlessofcomputerarchitecture.Javaisageneral-purpose，concurrent，class-based，object-orientedlanguagethatisspecificallydesignedtohaveasfewimplementationdependenciesaspossible.Itisintendedtoletapplicationdevelopers"writeonce,runanywhere,"meaningthatcodethatrunsononeplatformdoesnotneedtobeeditedtorunonanother.Javaiscurrentlyoneofthemostpopularprogramminglanguagesinuse,particularlyforclient—serverwebapplications，withareported10millionusers.[10］[11]TheoriginalandreferenceimplementationJavacompilers，virtualmachines,andclasslibrariesweredevelopedbySunfrom1995。

AsofMay2007，incompliancewiththespecificationsoftheJavaCommunityProcess,SunrelicensedmostofitsJavatechnologiesundertheGNUGeneralPublicLicense。

OthershavealsodevelopedalternativeimplementationsoftheseSuntechnologies，suchastheGNUCompilerforJavaandGNUClasspath.

Contents

1History

1。

1Principles

1.2Versions

2Practices

2.1Javaplatform

2。

1。

1Implementations

2。

1。

2Performance

2。

2Automaticmemorymanagement

History

Seealso：

Java（softwareplatform）#History

JamesGosling，MikeSheridan，andPatrickNaughtoninitiatedtheJavalanguageprojectinJune1991。

［12]Javawasoriginallydesignedforinteractivetelevision，butitwastooadvancedforthedigitalcabletelevisionindustryatthetime.[13］ThelanguagewasinitiallycalledOakafteranoaktreethatstoodoutsideGosling’soffice;itwentbythenameGreenlater,andwaslaterrenamedJava，fromJavacoffee,saidtobeconsumedinlargequantitiesbythelanguage’screators.［14]GoslingaimedtoimplementavirtualmachineandalanguagethathadafamiliarC/C++styleofnotation。

[15]

SunMicrosystemsreleasedthefirstpublicimplementationasJava1。

0in1995.Itpromised”WriteOnce,RunAnywhere”（WORA）,providingno—costrun—timesonpopularplatforms.Fairlysecureandfeaturingconfigurablesecurity,itallowednetwork-andfile—accessrestrictions。

MajorwebbrowserssoonincorporatedtheabilitytorunJavaappletswithinwebpages，andJavaquicklybecamepopular.WiththeadventofJava2（releasedinitiallyasJ2SE1。

2inDecember1998–1999），newversionshadmultipleconfigurationsbuiltfordifferenttypesofplatforms.Forexample，J2EEtargetedenterpriseapplicationsandthegreatlystripped—downversionJ2MEformobileapplications（MobileJava）。

J2SEdesignatedtheStandardEdition。

In2006,formarketingpurposes，SunrenamednewJ2versionsasJavaEE，JavaME，andJavaSE，respectively。

In1997,SunMicrosystemsapproachedtheISO/IECJTC1standardsbodyandlatertheEcmaInternationaltoformalizeJava，butitsoonwithdrewfromtheprocess。

[16]Javaremainsadefactostandard,controlledthroughtheJavaCommunityProcess.[17]Atonetime，SunmademostofitsJavaimplementationsavailablewithoutcharge,despitetheirproprietarysoftwarestatus。

SungeneratedrevenuefromJavathroughthesellingoflicensesforspecializedproductssuchastheJavaEnterpriseSystem.SundistinguishesbetweenitsSoftwareDevelopmentKit（SDK）andRuntimeEnvironment（JRE）（asubsetoftheSDK）；theprimarydistinctioninvolvestheJRE’slackofthecompiler，utilityprograms,andheaderfiles。

OnNovember13,2006,SunreleasedmuchofJavaasfreeandopensourcesoftware，（FOSS）,underthetermsoftheGNUGeneralPublicLicense（GPL）。

OnMay8,2007，Sunfinishedtheprocess，makingallofJava’scorecodeavailableunderfreesoftware/open—sourcedistributionterms，asidefromasmallportionofcodetowhichSundidnotholdthecopyright。

［18］

Sun'svice-presidentRichGreensaidthatSun'sidealrolewithregardstoJavawasasan”evangelist。

”[19]FollowingOracleCorporation'sacquisitionofSun

Microsystemsin2009–2010,Oraclehasdescribeditselfasthe”stewardofJavatechnologywitharelentlesscommitmenttofosteringacommunityofparticipationandtransparency”。

[20]Javasoftwarerunsonlaptopstodatacenters，gameconsolestoscientificsupercomputers.Thereare930millionJavaRuntimeEnvironmentdownloadseachyearand3billionmobilephonesrunJava。

［21］OnApril2,2010，JamesGoslingresignedfromOracle.［22］

Principles

TherewerefiveprimarygoalsinthecreationoftheJavalanguage：

［23］

1。

Itshouldbe”simple,object—orientedandfamiliar”

2。

Itshouldbe”robustandsecure”

3。

Itshouldbe"architecture-neutralandportable"

4。

Itshouldexecutewith”highperformance"

5.Itshouldbe"interpreted,threaded，anddynamic”

Versions

Mainarticle:

Javaversionhistory

MajorreleaseversionsofJava,alongwiththeirreleasedates:

JDK1。

0（January23，1996）

JDK1.1（February19,1997）

J2SE1.2（December8,1998）

J2SE1.3（May8，2000）

J2SE1.4（February6，2002）

J2EE5.0（September30，2004）

JavaSE6（December11,2006）

JavaSE7（July28,2011）

Practices

Javaplatform

Mainarticles：

Java（softwareplatform）andJavaVirtualMachine

OnecharacteristicofJavaisportability,whichmeansthatcomputerprogramswrittenintheJavalanguagemustrunsimilarlyonanyhardware/operating—systemplatform.ThisisachievedbycompilingtheJavalanguagecodetoanintermediaterepresentationcalledJavabytecode,insteadofdirectlytoplatform—specificmachinecode.Javabytecodeinstructionsareanalogoustomachinecode，butareintendedtobeinterpretedbyavirtualmachine（VM）writtenspecificallyforthehosthardware。

End—userscommonlyuseaJavaRuntimeEnvironment（JRE）installedontheirownmachineforstandaloneJavaapplications，orinaWebbrowserforJavaapplets。

Standardizedlibrariesprovideagenericwaytoaccesshost-specificfeaturessuchasgraphics,threading,andnetworking。

Amajorbenefitofusingbytecodeisporting。

However，theoverheadofinterpretationmeansthatinterpretedprogramsalmostalwaysrunmoreslowlythanprogramscompiledtonativeexecutableswould。

Just—in-Timecompilerswereintroducedfromanearlystagethatcompilebytecodestomachinecodeduringruntime.

Implementations

SunMicrosystemsofficiallylicensedtheJavaStandardEditionplatformforLinux,［24]MacOSX,［25]andSolaris。

InthepastSunlicensedJavatoMicrosoftbutthelicenseexpiredwithoutrenewal.［26]BecauseWindowsdoesnotshipwithaJavasoftwareplatform,anetworkofthird-partyvendorsandlicensees[27]developthemforWindowsandotheroperatingsystem/hardwareplatforms。

Sun’strademarklicenseforusageoftheJavabrandinsiststhatallimplementationsbe”compatible”。

ThisresultedinalegaldisputewithMicrosoftafterSunclaimedthattheMicrosoftimplementationdidnotsupportRMIorJNIandhadaddedplatform-specificfeaturesoftheirown.Sunsuedin1997，andin2001wonasettlementofUS$20million，aswellasacourtorderenforcingthetermsofthelicensefromSun。

［28]Asaresult,MicrosoftnolongershipsJavawithWindows,andinrecentversionsofWindows,InternetExplorercannotsupportJavaappletswithoutathird—partyplugin.Sun,andothers,havemadeavailablefreeJavarun—timesystemsforthoseandotherversionsofWindows.

Platform—independentJavaisessentialtotheJavaEEstrategy,andanevenmorerigorousvalidationisrequiredtocertifyanimplementation.Thisenvironmentenablesportableserver-sideapplications,suchasWebservices,JavaServlets，andEnterpriseJavaBeans,aswellaswithembeddedsystemsbasedonOSGi，usingEmbeddedJavaenvironments。

ThroughtheGlassFishproject，Sunisworkingtocreateafullyfunctional，unifiedopensourceimplementationoftheJavaEEtechnologies。

SunalsodistributesasupersetoftheJREcalledtheJavaDevelopmentKit（commonlyknownastheJDK）,whichincludesdevelopmenttoolssuchastheJavacompiler，Javadoc,Jar,anddebugger。

Performance

Mainarticle:

Javaperformance

ProgramswritteninJavahaveareputationforbeingslowerandrequiringmorememorythanthosewritteninC.[29]However,Javaprograms'executionspeedimprovedsignificantlywiththeintroductionofJust—in-timecompilationin1997/1998forJava1.1,［30]theadditionoflanguagefeaturessupportingbettercodeanalysis（suchasinnerclasses,StringBufferclass,optionalassertions，etc.）,andoptimizationsintheJavaVirtualMachineitself,suchasHotSpotbecomingthedefaultforSun’sJVMin2000。

Currently（November2011）,Java2.0codehasapproximatelyhalftheperformanceofCcode.［31］

SomeplatformsofferdirecthardwaresupportforJava;therearemicrocontrollersthatcanrunJavainhardwareinsteadofasoftwareJVM，andARMbasedprocessorscanhavehardwaresupportforexecutingJavabytecodethroughitsJazelleoption。

Automaticmemorymanagement

Javausesanautomaticgarbagecollectortomanagememoryintheobjectlifecycle.Theprogrammerdetermineswhenobjectsarecreated,andtheJavaruntimeisresponsibleforrecoveringthememoryonceobjectsarenolongerinuse。

Oncenoreferencestoanobjectremain，theunreachablememorybecomeseligibletobefreedautomaticallybythegarbagecollector.Somethingsimilartoamemoryleakmaystilloccurifaprogrammer’scodeholdsareferencetoanobjectthatisnolongerneeded,typicallywhenobjectsthatarenolongerneededarestoredincontainersthatarestillinuse.Ifmethod