2023年Java英文面試題經(jīng)典

英文Ｊavａ面試題Qｕesｔion:Whａt(yī)istｒａｎsieｎtｖarｉaｂlｅ?Answer:Trａｎsientvariableｃaｎ'tbeserｉａlize.FｏrｅxａmpｌeifavariableｉsdeclaｒedasｔransiｅntｉnａSeｒiａlizabｌｅclａｓsaｎdthecｌaｓｓｉｓwrittｅｎtｏａnObjectStreａm,thevaｌueｏfthevａriabｌｅcan'tｂewrittentｏthｅsｔｒeaminsｔeadｗheｎthecｌassisｒetrｉeveｄｆｒｏｍthｅＯbjectSｔreamthevalueofthevaｒiablｅbecomeｓnull.Queｓtion:NameｔheｃoｎtaineｒswｈｉchｕseｓBｏrderＬayｏutａsｔｈeirdｅfaｕltlaｙouｔ?Ansｗｅr:ＣontａｉnerｓｗｈｉchuｓesBｏrderLayoｕtａsｔheiｒdefaultarｅ:windoｗ,FrameaｎｄDialoｇcｌasses.Qｕestｉon:WhatdoyouｕnderstandｂySｙncｈronizatioｎ?Ａnsｗer：Syncｈronizatiｏｎｉｓａproceｓsｏfcoｎtroｌlingtheaccｅssofshareｄｒesourceｓbｙｔhemuｌtｉｐlethreadsinsuchamannｅrthatoｎlyoｎethｒeadcanaccesｓoｎｅreｓoｕrcｅａt(yī)ａｔｉme.Ｉnnonsynchrｏnｉｚedmｕltｉthｒｅaｄedapplication,iｔisｐｏssibleforｏｎethreadtomodiｆｙaｓharedｏｂjectwhiｌeａnotheｒtｈreaｄisinｔheproｃessｏfuｓingｏruｐdaｔiｎgtheobjｅｃt'svalｕe.Synchrｏnizatioｎpreｖeｎtssuchtypeoｆdaｔaｃｏrruｐtion.E．g．Synｃhronizｉngaｆｕnction:ｐｕblicｓynchｒoｎizedｖｏidMｅthod１(）{/／Appｒoｐriａt(yī)eｍｅｔhｏd-relatedcoｄｅ.}E.g.Syｎchrｏniｚingablockｏfcodｅiｎsideafｕnctｉon:publｉcmyFuｎcｔion（）{syncｈronized(ｔhis){//Synchroniｚｅdcｏdeherｅ.｝}Quesｔion:WhatｉsCｏllectionＡPＩ?Anｓwer:TｈeＣolleｃｔionAＰIiｓａsｅｔｏfｃlassｅsandｉntｅｒfacｅsthatsuｐporｔoperaｔｉｏnoncollectiｏnsｏfobjecｔｓ.Theseｃｌaｓsesanｄinterfacｅsaｒemｏｒeｆleｘible,morepoweｒful,anｄmorerｅｇularｔhaｎthevectoｒｓ,arｒａys,ａｎｄｈaｓｈｔａblesifeｆfecｔivelyreplａｃes.Ｅｘampleofｃｌａsｓes:HａshSｅt,ＨashMap,AｒrayＬist，LinkedLiｓt,ＴｒeeＳetandTrｅeＭap.Ｅxａmpleｏfinｔeｒfacｅs:Ｃollectｉoｎ，Set,LiｓtandMａp.Ｑuesｔiｏn：ＩsＩteｒａｔoraClasｓｏrＩｎteｒface？Whatｉsitsｕse?Ａnswer：ＩteratoｒｉsaninteｒfaceｗhicｈisｕｓｅdtostepｔhrｏuｇｈｔheｅｌemeｎtsoｆaCｏlｌｅctｉon.Question:Ｗhaｔｉｓsimｉlariｔies/ｄifｆereｎcｅbｅtweｅｎａｎA(yù)ｂstｒaｃtcｌaｓｓａnｄIｎterfacｅ?Anｓｗer:Difｆｅrenｃesａｒｅasfｏllｏｗs：Intｅrfａcｅsprｏvideaformofmｕltiplｅｉnhｅritanｃｅ.Aｃｌasｓcａnexｔendｏnlyｏneotherclａsｓ.Interfaｃｅsareｌｉmiｔｅdtopublicmeｔhｏdｓaｎdconsｔａntｓwithnoiｍｐleｍeｎｔation.Ａbstraｃtcｌassescaｎhaｖeａpartｉalｉmpleｍeｎtatｉｏｎ,prｏtｅcｔedparts,statｉcｍethods，etc.AＣｌaｓsｍayiｍplｅmenｔseveｒalinｔeｒfａceｓ.Ｂutinｃaseofabstｒactclass,ａclassｍaｙextendonlyoｎｅａbstractｃlass.Inｔeｒｆacesarｅslowａｓitｒeｑuirｅsexｔｒaindirｅctiontofindcorrｅｓpondingmｅｔhodiｎtheaｃtualcｌass．Aｂstraｃｔclaｓsｅsarｅｆａst.Siｍｉlaritｉｅs:NeｉthｅrAｂsｔｒaｃtclassｅsoｒInterfａcecanbeiｎstantiａt(yī)ｅd.Qｕｅstiｏn:HowtodefinｅanAｂsｔｒａｃtclａｓｓ?Answｅr:ＡclasscontainｉｎgabstｒactmethｏdiｓｃallｅdAbstrａｃｔclａｓs．AnAbsｔraｃtcｌasｓcan'ｔｂeinｓtaｎｔiated.ExamplｅofAbｓtractclａｓs：absｔrａｃtclassｔesｔＡbｓtractCｌａss｛pｒoｔｅctedSｔrｉｎgmyString；pｕbliｃSｔrinｇgeｔMyStｒｉnｇ(){reｔuｒｎｍｙＳtｒing;}publicabｓtｒａctstringanｙAbstraｃｔFuncｔｉｏn()；｝Queｓtiｏn：HｏｗtodｅfineanIntｅｒfａce？Ａnsweｒ:InＪaｖａInteｒfaceｄeｆiｎesthemeｔｈｏdsbuｔｄoeｓｎoｔｉmplｅmenｔthｅm.Interfacｅｃａnincｌudeconｓｔａnts.ＡｃlassｔｈatｉmｐｌemenｔstｈeinｔｅｒｆaｃｅｓｉｓｂounｄtoimplｅmentallthｅｍethｏｄsdeｆiｎｅdinIｎｔｅrface.ＥmａplｅoｆInｔeｒfaｃe:puｂlｉｃiｎｔeｒｆaceｓａmpleIntｅrｆaｃe{publicvoidfuｎcｔｉonOne(）;pｕbｌiclongＣＯＮＳTANT_ONＥ=１000;}Queｓtiｏn:ExplaｉnｔhｅuｓerｄefineｄExceptioｎs?Anｓweｒ：UｓeｒｄｅfｉnedEｘceptionｓaｒeｔhesｅpａrateEｘｃeptionｃlaｓsesｄｅfinｅdbyｔｈeｕseｒfｏrspecｉficｐurｐｏseｄ.Anｕｓerdｅfinedcancreatedbｙsimpｌysｕb-ｃlasｓｉngittotheExcepｔｉｏｎclaｓs．Ｔhｉsａllowsｃuｓtomexceｐtioｎstobegｅneratｅd(ｕｓingｔhrow)andｃａugｈtintheｓameｗayasnormalexceptionｓ.Ｅxamplｅ:clａssmyＣustomEｘｃeｐｔioｎextｅndsException{//Tｈeclasssｉmｐlｙhａstoexisttｏｂeａｎeｘｃｅｐｔion}Qｕesｔiｏｎ:ExplaiｎｔｈenewFeaｔuresoｆJDBＣ2．0CorｅAPI?Answeｒ:TｈeJDBＣ2.０APＩｉnｃｌudesｔｈecoｍpletｅＪDBCAＰＩ,wｈicｈincludeｓbothｃoreandＯptｉonalPacｋaｇeＡPI，ａｎdｐｒovidｅsｉnｄuctrｉａｌ-strenｇthdatabａsecomputingｃａpabiｌｉtieｓ．NewFｅaｔuresiｎJＤBＣ2.０ＣoreAＰI:Sｃｒollablereｓultｓets-usｉngｎeｗmethｏdsinthｅResultＳetiｎterfaceallｏｗsprogrａmmａt(yī)icａllymoｖeｔheｔopａrtｉculａｒrowortoapoｓitｉoｎreｌatiｖeｔoｉｔscuｒｒｅｎtpoｓｉｔioｎJDＢＣ２.0ＣoreAＰＩpｒｏviｄestｈeBatcｈＵpdatｅsfunctionａlｉtytothejａｖaapｐlicａt(yī)ｉonｓ.JaｖａapplｉcaｔiｏnscannowusethｅRｅsultSet.uｐdａｔeＸXＸｍethods．Nｅwdaｔatｙｐes－inｔerfaｃesmａｐpinｇtｈeSＱL3daｔａt(yī)ypesCusｔomｍａpｐｉｎｇofｕｓer-ｄefinedtｙｐes(ＵTDs)Misｃeｌlaneｏusfeaｔｕrｅs,incluｄingｐｅrfoｒmanceｈinｔs,thｅuseofcharacterstreams,fuｌｌｐｒeciｓiｏｎfoｒjavａ.ｍａt(yī)h.BigDecimaｌvaｌues,aｄｄitiｏnalsecurity,ａｎdｓuppｏrｔｆｏrtimezｏnesindate,time,andtimesｔamｐｖａlueｓ．Ｑuestioｎ:Exｐlaｉngarbagｅｃolｌection？Ａｎsweｒ：GarbagｅcｏlｌectionisoneoｆtｈｅmostｉｍportanｔfｅatuｒｅｏfＪavａ.GarｂａgeｃoｌlecｔioniｓalｓocａlledaｕｔomaticmｅmｏrymａnagemeｎｔａsJVMａutomatiｃalｌyreｍｏｖesthｅｕnuｓedvarｉａbles/ｏbｊeｃts(valｕｅisnuｌl)ｆromthememory.Ｕsｅrpｒｏgｒamcａnn'tdirｅcｔlyfreetｈｅobｊeｃtfroｍmemorｙ，ｉnｓteａｄiｔiｓtｈejｏbofthegａrbagｅcollectortoaｕｔomａt(yī)ｉcａllｙfreeｔｈeobjectｓｔhatａrenｏlongｅrrefereｎｃedｂｙaprｏgrａm.Everycｌassinheｒｉtsfinalize()ｍethodfｒoｍjaｖａ．lａng.Ｏｂｊect,thｅｆinalｉze()mｅｔhoｄiｓcalｌｅｄｂｙgarbａgecolleｃtorwhenitdeｔermｉneｓnｏｍorerｅferenｃｅsｔｏtheobjecｔｅxists．ＩｎＪava,iｔisgｏodideatoexpliｃitlyａssignｎullｉntｏavariablｅwｈｅnnoｍｏreｉnuｓe.IJavaoncaｌlｉngSyｓteｍ.gｃ()andＲuntｉme.gｃ()，JVMｔriestorecycletheｕｎusedobｊects,ｂuｔthereｉsｎoguａranteewhenallｔhｅｏbjectswiｌlgａrｂagecollecｔed.Qｕestion:Hｏｗyoucanｆoｒcetheｇarbagｅcolｌeｃtｉon?Ａnｓwer:Garbagecollｅctionauｔomaticprｏcessandcan'tbｅforｃｅd.Quesｔion:WhaｔisＯOPＳ？Aｎswｅr:ＯOＰisｔhｅcoｍmonabbｒeviaｔiｏnforObjecｔ-OrｉentedＰrogramming.Ｑｕeｓtion:DｅsｃriｂｅｔheｐｒinｃipleｓofOＯPS．Ａｎｓwｅｒ:TｈｅreaｒethreemainｐriｎcｉｐaｌｓｏfｏopswhicharｅcalledPolｙｍｏｒｐｈism,InheｒｉｔanceandEncapsｕｌａｔｉon.Queｓtｉon：ExpｌaintheEｎｃapsuｌationｐｒincｉpｌe.Aｎｓｗｅr:Enｃapsulatioｎisaproceｓsｏfbiｎdｉnｇorwrapｐinｇｔｈedａt(yī)aaｎdtheｃoｄestｈatoperatｅsoｎtｈedａt(yī)aintoasiｎgｌｅentｉty.Thｉｓkeepsthｅdatasａfefｒoｍoutsideinterfaｃeanｄｍisuse.Onｅwaｙｔｏｔhinkabouteｎcapｓulationisasapｒoｔeｃtivewｒａｐpeｒthatpreventscｏdeａｎddatafｒombeｉngarｂｉtrarilｙaｃcesｓedbyotｈeｒcoｄedｅfinedｏutsiｄetｈｅwrapper.Qｕｅstｉon:ＥxplaｉｎtheInherｉｔａnceprincｉｐle．Anｓwｅr:Ｉnheｒiｔancｅistheｐｒocesｓbywhichoneoｂjectａcquiresthepｒoｐｅrtiesofanｏｔｈerｏbject．Ｑuesｔion:ＥxplainthePoｌｙｍｏrpｈisｍｐｒincｉple.Ａnsｗｅr:ThemeaningoｆPolymorphｉsｍｉssomｅｔｈingｌikeoｎenameｍaｎyforms.Polymorphｉsmｅｎablesonｅeｎtiｔytobeusedａsasgeneralｃategoryfordifferenttypｅsofactionｓ.Tｈeｓpeciｆicactiｏniｓdｅterminedbｙｔheexａctnatureofｔｈesｉtuatｉon．Thｅｃonceptｏfpoｌymｏrpｈｉsmcanbeeｘplaｉnedas"ｏｎeiｎtｅrfacｅ,muｌtｉplemethｏds".Ｑｕｅｓtion：ExplainｔhｅdifferentfｏrmｓofＰolyｍorphiｓm.Aｎｓｗer:Fromapｒactiｃalprogｒammingviewpｏinｔ，polyｍoｒphismｅｘistsｉｎthｒeeｄistｉncｔｆormsiｎJava：MethodoveｒｌｏadｉnｇＭeｔｈodoveｒridingｔhrougｈiｎhｅritanceMethｏdoveｒridiｎgｔhｒoughthｅJavaｉnterfａceQuestion:ＷhataｒeAcｃeｓsSpecifiersavaiｌaｂｌeｉnJava?Ａｎswer:Accesssｐecifｉersarekeywｏｒdsthａt(yī)dｅtermｉnestheｔｙpeｏfaｃcessｔothemembeｒｏfaclass.Tｈｅｓeare:PｕblicProtectedPrivatｅDefaultsQuesｔion:DescｒibｅtheｗrapperｃlasｓesinJａｖａ．Aｎswer:Wｒａpperｃlａssisｗrａpｐeraｒouｎdaprimitivｅｄataｔype.Ａnｉnsｔａnceofawraｐpｅrclaｓsｃｏntains，orwrａｐｓ，apriｍitivevalueoftｈｅcorrespondinｇtype．Ｆoｌlowinｇtabｌeliststｈｅprｉｍiｔiveｔypeｓaｎｄｔｈｅcorreｓｐondｉnｇｗrapperclａsｓeｓ：ＰrimitiveWｒａpperbｏｏleanjava.laｎｇ.Ｂooleanbｙtｅｊava．lanｇ.Ｂytｅｃharｊava．lａng．Characterｄｏｕbleｊａva.lａng.Doubleｆｌoatｊava.lａng.Ｆloatintｊavａ.lang.Inｔegeｒlongjaｖa．lａｎｇ.Longshortｊava．ｌａnｇ.Ｓhoｒｔvoidｊａｖa.ｌａng.VoidＱｕestion:Readｔhefolｌowingprogrａｍ:publicclassteｓt{pubｌicsｔaｔicｖoidmaiｎ(Strｉng[］arｇｓ){ｉｎtx＝3;iｎty=1;iｆ（x=y)Systｅm.out.pｒintln（＂Notequａl");elseSｙstem.ouｔ.ｐrintｌｎ("Equａｌ");}｝Ｗhatｉｓtheresｕlt?A.Ｔｈｅouｔｐutｉsｅqual?br＞B．TheｏｕtpｕtｉnnｏtEｑual?ｂｒ>C．Anerroｒat"if(x=ｙ)＂cauｓescｏmpilatiｏntｏfalｌ.D．Theprogｒaｍeｘｅｃuteｓbutｎooutｐutiｓshowonconsｏle.Anｓｗer:CQuｅstioｎ:ｗｈａt(yī)iｓtheｃlasｓvaｒiables?Answｅr:Whenｗecreaｔeaｎｕmｂerofobjectsoftｈesamecｌａｓs，theneachｏbｊectwｉlｌｓhａｒeａｃommｏncoｐyofvａｒiables.Thatmeａｎsｔhattheｒeiｓoｎlｙoｎecopypｅrｃlａss,ｎomaｔｔerhowmａnyoｂjeｃｔsarecreａt(yī)edfromit．Ｃlaｓｓvａrｉａblesｏｒstａｔicvariabｌesaredeｃlaredwiththesｔatiｃkｅyｗorｄinａclａss,bｕtminｄitthatitｓｈouldbedeclaｒedｏｕtsiｄｅouｔsideaclａss.Theseｖａriablｅsarestoredｉｎsｔaticmeｍory．Classvariａblesaｒemoｓtｌyｕsｅdｆorcｏnｓtａｎts,variａblｅthaｔneverchａnｇeiｔsinitｉａlvalue．Staticvａｒiａblｅｓarealwaysｃalledｂythｅclａssnamｅ．Thiｓvariaｂleｉscreａt(yī)edwhｅnｔｈeprｏｇramｓtartsi．e．ｉtiscreatｅdbeforetｈeinstａnｃeiscrｅatedofｃｌａｓsbyusingnewoperaｔorａndgetｓdestｒoyedｗheｎtheprogramsｓｔops.Thｅｓｃopeofｔｈeclaｓsvａriableiｓsaｍeａinｓtancevａｒiａble.Thｅｃlasｓvarｉabｌecanbeｄeｆｉnｅdａnywｈｅreatｃlasslｅｖelwithtｈeｋeyｗorｄｓtatiｃ．Ｉtinｉtiａｌvaｌueissamｅａｓｉnsｔａｎceｖariａblｅ.Wheｎtheclassvａrｉａbleisdeｆinｅdasinｔthｅnｉt'sｉniｔialvａlueisｂydefaultzeｒo,whenｄeｃｌarｅdbooleａｎiｔsdefauｌtvａluｅｉsｆaｌseａnｄｎuｌｌforobjｅcｔreｆｅｒences.Ｃlａssvariablｅsareａssocｉaｔｅdwｉthtｈeｃlaｓs,ｒａt(yī)hｅrtｈａnwithanyobjｅct.Question:Whaｔｉｓthｅdｉｆfｅrenｃebｅtweentheｉnstａnceofaｎdgｅtclａｓs,theseｔwoaｒeｓａmeorｎｏt？Ａnsweｒ:instanceofisａoperaｔor，ｎｏtafｕnｃtiｏｎwhileｇetClassｉsamｅthodofｊavａ.lang.Ｏbjｅｃtｃlaｓs．Coｎsidｅｒａｃondｉtioｎwhｅreｗeuseｉf（o.gｅtＣlasｓ（)．getＮamｅ(）．ｅｑuaｌs(＂java.ｌａｎg.Mａt(yī)ｈ")){}Ｔｈismethｏｄonlｙｃheｃksｉfｔhｅclassnameｗehavepassｅｄiｓｅqualtｏjaｖａ.lang.Ｍath.Theｃlａssjavａ.ｌang.MaｔｈｉsｌｏａdeｄbytheｂootsｔrapClassLｏader.Tｈｉｓｃlassisaｎaｂstrａctｃlａss．Thｉscｌaｓsloaderiｓrｅspoｎsibｌeforloａdingclasｓes.EveryClasｓobjectcｏntainsareｆerｅncｅtothｅClassＬoadertｈatｄｅfines.gｅtCｌass（)ｍｅthｏdretｕrnsthｅｒｕnｔimecｌassoｆanｏｂject.Itfetcｈeｓthejaｖaｉｎsｔanceｏｆtｈegivenfullyｑualifiedtypename.Thecｏdeweｈaｖewriｔteｎiｓnoｔｎeｃessary,becaｕｓewｅshoｕｌdnｏtcomｐarｅｇｅｔClaｓs.getＮaｍｅ（).TheｒeasonｂehinditisｔhatiftｈetｗodifｆeｒenｔclaｓsloadersｌoadtheｓamecｌassbuｔｆorthｅJVM，itwiｌlcｏｎsiｄerboｔhclaｓsesasdifferenｔclａssesso,wecan＇tｃompａretｈeiｒnaｍes．Iｔcanoｎlygivestｈeimpleｍentiｎｇclassbutcan＇tcｏmpａreainｔerfacｅ，bｕｔｉnｓｔanｃeoｆopｅrａｔｏｒcan.Theinstaｎｃeｏfoｐeratorcｏｍparｅｓanobjecttoaspecifｉｅdtyｐe.Ｗecaｎuseiｔｔotestifａnoｂｊecｔisanｉnstａnceofaclass,aninstaｎceoｆａsuｂclａss,oｒａniｎstanceofaclａsｓtｈatimｐｌemｅｎtｓaparｔiculariｎｔｅrfaｃe.WeshｏuldｔrytｏｕｓｅｉnｓtancｅofopeｒatorinplaceoｆgｅｔCｌaｓs()method.ＲｅｍｅmberiｎｓtanceofopeaｔorａｎdgetClassａrenotsame.Ｔrytｈisexample,itwillhelpｙoutobeｔterunｄersｔaｎdtｈｅdiffｅrencｅbeｔｗｅenthetwo.Ｉｎterｆaｃeone｛｝CｌassTwoiｍｐlｅmentsoｎe{}ClasｓTｈreｅｉmpleｍenｔsｏｎe{}pｕblicｃlassTesｔ｛puｂlicｓtatiｃvｏｉdｍａin（Striｎgargs［］）｛onｅtesｔ1=neｗTwo（);onetｅst２=newTｈree();Ｓystｅm．out.priｎtln（tｅst1inｓtａncｅｏfonｅ）;／/ｔrｕeSystem.out.pｒｉntln（teｓt2ｉnstanceoｆｏnｅ）;//trueＳystem.ｏｕt.printｌn(Teｓｔ.gｅtＣlass(）.equals(tｅst２．ｇetClaｓｓ()));／／false}}＊Q1．HoｗcouｌdJavaclａssesdirectprogｒammessａｇeｓtoｔhesｙstｅmconsoｌｅ,buｔerrormesｓagｅs,sａｙtoaｆｉｌe?．TheｃlaｓsSystemhaｓａvaｒiableｏutthaｔrepreｓentstheｓｔａｎdaｒdｏuｔpｕt,anｄtheｖaｒiablｅｅrrｔｈatrｅｐresｅntstｈｅstanｄaｒｄｅrrordevｉce．Bydeｆａult,theyboｔhpｏintatｔｈesyｓtemcoｎsole.Thｉshｏwtｈesｔａｎｄardouｔputcｏuｌｄｂeｒe－ｄireｃtｅd:Stｒeamst=ｎewＳtreａｍ（ｎewＦｉｌeOｕtpuｔＳtream("output.txｔ"));Sｙstｅｍ.seｔＥrr(sｔ)；Ｓyｓｔeｍ.setOuｔ(st);*Q２．What'stｈedｉfｆerenceｂｅtｗeeｎanｉnterfaceａndanabｓtｒactｃlass?A.Ａnａｂｓtractcｌasｓmａycｏntaincｏdｅｉnmetｈｏｄbodieｓ，whｉｃｈｉsnotallowedinaｎｉnteｒfaｃe.Wiｔｈabsｔｒactcｌasses,yｏuhavetoｉnｈerityｏｕrclassfromｉｔaｎｄJavadoesnoｔalｌoｗmｕltipleｉｎhｅｒｉtanｃe．Ｏntheotherhand,yｏucanimplementｍｕltipleｉnterfaｃesｉnｙourclasｓ.＊Q3.Wｈｙwouldyｏｕuseａsyｎchronizｅdbloｃkvs.synｃhroniｚedmｅｔhｏｄ?A．Synchrｏnizeｄblocksplaｃeｌocksforｓhorterperiodsｔhansｙncｈｒoｎizedmｅｔhoｄｓ．*Q4．Ｅxplaintheusageoｆtheｋeywordtransient?A.Tｈiskeyworｄiｎdicａt(yī)ｅsthaｔｔｈｅvalｕeofｔｈismeｍbｅrｖariａbleｄoeｓnoｔhaｖetｏbesｅｒiaｌizｅdｗiｔhtheoｂjｅct.Ｗｈentheclasswｉllbedｅ－seriａlized,ｔhisvａｒiablewillbeｉniｔiaｌｉzedwitｈadeｆauｌtvaluｅofitsdatａt(yī)ype(i．e.zeroｆｏrｉnｔegerｓ）.*Ｑ5.Howcａnyouｆoｒcegarbagecｏllｅction？Ａ.Yoｕcan'tforcｅGC，butcｏuｌdrequｅstitbyｃaｌlinｇSyｓtem．gc(）.JVMdoｅsｎｏtguａranteeｔｈａt(yī)GCｗilｌbestａｒｔedimmeｄｉａt(yī)ely．*Q6.Howdoｙｏuknowifaneｘplicitobjecｔｃastｉｎｇisneeｄed？A．Ifyｏuassｉgnasuperclasｓobjecttoavａriableofａｓｕbcｌass'sdatatypｅ,younｅｅｄtodoｅxpliｃitcasｔing.Foｒexampｌe:Objecta;Custoｍerb;ｂ=(Cuｓｔｏmｅr）a;Whenyouaｓsignasuｂclasstｏavaｒiablｅhavinｇaｓｕpｅclａｓstｙpe,thecasｔiｎgisｐeｒfｏrmedautomaｔically．*Q7.What'sthediffereｎcebetｗeeｎtheｍｅtｈodssleep()aｎdwait（）Ａ．Thｅｃｏdeｓlｅep（1000)；putstｈreaｄasidefoｒｅｘaｃｔlyonesｅｃond．Ｔhecoｄewait(１000）,cａuｓesawaitoｆuｐtoonｅsｅcond．Ａtｈreａdcoｕldｓtｏpwaitinｇeａrlierｉfitreceiｖｅsthｅnｏtify(）ｏrｎoｔifyＡｌl()call.Themetｈodwａit()ｉsｄefｉnedintheｃlassＯbjｅctanｄthemetｈodsleｅp()isdefｉnedintheclasｓThreａd.*Ｑ8．CａnｙｏｕｗritｅaJavaclasstｈatcouｌｄbeuｓedｂothａsaｎａppleｔａｓｗellasaｎappliｃatiｏn?A．Ｙes．Addaｍain()methodｔotｈeapｐlet.*Ｑ9.Ｗhａt(yī)'ｓｔｈedifｆerencebetwｅenconsｔructorｓａnｄothermethods？A.Ｃonstrｕctorｓmusｔhavetheｓaｍeｎaｍeasthecｌａｓsandcａnnotreturnavalｕｅ.Theyａreoｎlycaｌleｄoncewｈilｅregｕｌarmｅthｏdsｃouldｂecalｌedmaｎyｔiｍeｓ.*Q１0.CａnｙoucalloneconstructｏrｆroｍanｏtherｉfaclasshasmｕltiｐｌecｏnstructorsA．Ｙes.Uｓeｔｈis()syｎtax.*Q11．ExplaintheｕsaｇeofJaｖaｐacｋages.A.Thisiｓawaytoorganizefileswｈenａｐrojｅctcoｎsistsｏfmultiplemｏｄulｅs．Iｔａlsohelｐsresolvenamingcｏｎfｌictswhｅndiｆfｅrentpaｃｋagesｈaveclａssesｗｉththeｓａmenaｍeｓ.Ｐackageｓａccesｓlevｅｌａlsoalｌowsyoｕｔoprotｅctｄataｆｒombeingusedbythｅnon-autｈorizedclasses.*Q1２.Ifaｃｌaｓｓｉslocatｅｄinaｐackａge,whａt(yī)ｄoyouneedｔｏｃｈａngeinｔheＯSeｎvironmenttｏbeablｅtｏuseit？Ａ.YｏｕnｅeｄtoaｄｄadirｅｃtｏｒyｏrajarfiｌetｈatcontainsthepackagedireｃｔoriｅstotheCＬASSPＡＴHｅnｖironmｅntvariabｌe.Let'ssayaclassEmplｏyeebeloｎｇstoapackagecoｍ.ｘyz.hr；aｎｄｉslocatｅdｉｎthefilec:\dｅv\cｏm\xyz\ｈr\Employee.jａvａ.Inｔhisｃase,you'ｄneedtoaddc:\ｄeｖtｏｔheｖaｒiableCLASＳPATH.Ifthisclassconｔaｉnsthemethｏｄmain(）,yｏucouldｔestitfromacoｍmandpｒomptｗinｄｏwasfoｌlowｓ:c：＼＞javacom.ｘyz.hｒ.Employｅe*Q13.What'ｓthedifｆｅreｎcebetweｅnJ2SＤK1．５ａndＪ2SDＫ5.０?A.Tｈeｒe＇snodiｆfｅｒenｃｅ,SuｎMicrosyｓtemｓjustre－braｎｄｅdthiｓversion．＊Q14.WhatwｏｕｌdyｏuusetocompareｔｗoSｔriｎgvarｉａbｌeｓ-theopｅraｔor=＝oｒtheｍethodeqｕals（)？A.Ｉ＇dｕｓethｅmeｔｈodequalｓ()ｔoｃompaｒethevaluesofｔheＳtｒingsaｎdthe=＝tocheckifｔwovaｒiabｌｅsｐoｉntatthesaｍeinstancｅｏfaＳｔrｉngobject．*Q1５.Doｅsｉtmatteｒinwhａt(yī)oｒｄercatchstateｍentsｆｏｒFileNotＦoｕndExcｅpｔionandIOExceｐtiｐｏｎarewｒｉtteｎ?A.Yeｓ，itdoes．TｈeFileNoFounｄExｃｅptiｏｎisiｎheritedfromtheIOException.Exception'ssuｂclaｓsｅshavetoｂecａughｔfｉrｓt.*Q16.Cａnaninnerclaｓsdeclａredinsideoｆamethodaccessloｃａlvarｉａblesofthiｓｍethｏｄ?A.It＇spｏssｉbleifthesevariaｂlｅsarefinal.＊Q１7.Whatcangoｗrongifyoureplace＆&ｗiｔh&inthefｏｌｌｏwinｇｃoｄe:Strｉnga=null;if(a!=ｎulｌ&&a.ｌengｔh()>１０）{...}Ａ.AsinｇleamperｓandｈeｒｅwouldleadtoａNullPｏｉnｔerExceptiｏｎ．*Ｑ18．Wｈaｔ'sthemaiｎdifferenｃeｂetweeｎａVecｔorandａnArｒayLisｔA．ＪaｖaＶeｃtorcｌaｓsiｓｉnｔeｒnａlｌysynchronizｅdandArrayLｉstiｓｎot.＊Ｑ19．WｈenshouldｔhｅmeｔhｏdiｎvokeLaｔer()bｅuｓeｄ？A.ＴｈismethoｄｉsusedtoensuｒｅthaｔSwinｇcoｍpoｎentsａｒeuｐdatｅdtｈrougｈｔｈeevent-dispａt(yī)chingthreａd.*Ｑ20．Hｏwcaｎaｓｕbcｌasｓcallaｍｅthodoraｃonstｒｕctordefｉneｄiｎasuperｃlass?A.Usｅthefolｌowingｓｙｎtax:supｅｒ.mｙMethod();Ｔocallaconｓtructoroｆthesｕｐerclaｓs,ｊｕsｔwritesuｐer();iｎｔｈｅfiｒstｌiｎeofthｅsuｂcｌaｓs＇sconｓtrｕｃtoｒ．Fｏrseｎior-leveｌdevｅlｏpers:**Q21.What'sthedｉfｆereｎcebetｗeenaqueueandastacｋ?A.Ｓtacksｗｏrｋsbylａst－iｎ-ｆirst-ｏｕtｒule(LIＦO),wｈileｑueuｅsuseｔhｅFIFＯｒuｌｅ＊*Q２2．Youｃancreateanａbstrａctclａssthatcｏｎｔａiｎｓｏnlyａｂstractmetｈodｓ.Onｔheｏｔｈerhand,yｏucancreateaninterfaｃethａt(yī)ｄeｃlareｓｔhesamｅmethｏdｓ.Socanyouｕseabstractｃlaｓseｓiｎsteａdofｉnterfaｃｅｓ?A．Sometimes.Butyouｒclassmaｙbeａdescｅndeｎｔofanotherclaｓｓandinthiscasetheiｎtｅrfaceiｓyｏuｒonlyopｔion．**Ｑ２3.WｈatcomesｔomｉndｗhenｙｏuheａｒaｂｏutayoungｇeneratｉoｎinＪava?Ａ．Gａrｂagecoｌlecｔｉon.*＊Ｑ24.ＷhatcomｅstomｉｎｄｗhenｓｏｍeｏnemｅntionsashａllowcoｐyiｎJaｖａ?A.Objeｃtcloｎinｇ.**Ｑ25.Ifｙou'rｅｏverridinｇthemｅthoｄequａls()ofanobject,ｗhｉcｈotherｍethｏdｙoumｉgｈtaｌsoconsider？A.ｈaｓhCode(）*＊Ｑ２６.Yｏｕareplanniｎgtｏdoａnｉｎｄｅxｅdｓeａrchinaliｓtｏｆobｊectｓ.WｈiｃhoｆthｅtwoＪaｖacollｅctiｏｎssｈouｌｄyouuｓe:ArｒayLｉsｔorLiｎｋｅｄＬist?Ａ.ＡrrayList＊*Q27.HoｗwoｕｌdｙoｕｍakｅacｏｐyｏfanentireJaｖaobjｅcｔwithitsstａt(yī)ｅ?A.HavｅthｉｓcｌａｓｓiｍpleｍenｔCｌoneableinterfaceaｎｄcallｉtsmｅthodｃlｏｎe()．＊*Q2８.Howcaｎyouminimｉzethｅneedofｇarbａgeｃｏｌlｅcｔionandmａkｅtｈememoｒyuseｍoreeffective？A.Ｕsｅoｂjectｐoolingａndwｅakobjｅctrefｅrencｅs.＊*Q２9．Thｅreａrｅtwｏclasses:AanｄＢ.ThecｌaｓｓBneｅdtoinfｏrmaｃlaｓｓAwhｅｎｓomeiｍｐoｒtantevenｔhａshａppｅned.WhatJａｖatechniqueｗouldｙoｕusetoimpleｍentiｔ？Ａ．IftheseclaｓｓesareｔｈreaｄsＩ'dcｏnｓｉｄｅrnotiｆy（)ornotiｆyAll()．FoｒreguｌarclasｓesyoｕcａnｕsetheＯbsｅｒverinteｒｆaｃe.**Q30.Whａｔａcｃｅsslｅveldoyounｅeｄｔospeｃifｙinｔheclａssdeｃｌarationtoeｎsurethatonｌｙclａssｅsｆromtheｓamedｉrectoryｃaｎａcｃｅｓsit?A.Youdｏｎｏｔｎｅeｄtospｅcｉｆｙanyaｃｃｅｓsｌｅvel,andJaｖａｗilｌuseadefaultｐａckageaｃcｅssleｖeｌ.ＴheJ2EEquestionsarecomｉngsoon.SｔaytｕｎeｄfoｒYaｋｏvFaiｎｏnLiveSYS-ＣON.ＴV．AｓkyｏurqｕestiｏnstｏＹａｋovoｎｔheaｉr!====＝==＝=＝===＝＝＝====＝IBMjavａ英文面試題1.whａt(yī)isoraｃlｅ.2.wｈaｔiｓmajordifｆereneceoｒaｃlｅ8ｉaｎdorａｃle9i．4．teｌlｍesoｍｅtｈinｇｕrsｅｌf.5.pｌeaseｔeｌlmeaboｕtｏｏps.6．whatｉｓsｉｎgleｉnheritａｎcｅ．7.whａｔisｍultiｐleinhｅritaｎcｅ.8.ｃanjaｖasupｐorｔmultipｌeiｎheritａncｅ.9．whａt(yī)isinterｆace.10．whａt(yī)isdiffereｎecbetwｅeｎabstrａctcｌassａｎｄiｎterfａce．１１.ｈowtoｕｐrovethatabstraceclassｃanｎoｔｉnstantiatｅdｉｒｅctly.12.whaｔisｄｉｆferenecebeｔweｅnstｒingaｎｄstrｉngbuffｅｒ．13.whａｔisiｍmutabｌe1４.howtｏwrｉteaproｇramｕsingsｏrtｐrｏgｒam．１５ｈowtｏｗritｅaprogｒamusingｕｎsｏrtpｒoｇraｍ．１６.whatisｌegacy.１7．wｈatiｓlegacyａｐi18.wｈaｔiｓｌegacyｉntｅｒface．19.ｗhatismaindifｆereｎcehａshｍａpaｎdhastaｂle２０.ｗｈａｔismａindifｆerenｃeｂｅｔｗeｅnaｒrayliｓtａndｖector.２1.ｗhaｔｉsｓtrutsframeｗｏrk.22.wｈataredｉsｔｒibuteｄｔｅchonologｉes.23.whatisaｄｖaｎｔageanｄdisadvａntageofdｉstributeｄtechoｎｏｌoｇies.24.ｗhatismａindifｆerencebeｔweenjｓｐａndｓervｌｅｔs.25.whatiｓdifferｅｎcebeｔweｅｎｐｒoｃedureanｄｆuｎcｔions．２6.wｈaｔiｓjdbc.27．whaｔaretypeofdrivｅrｓ.２８．whatｉstｙｐe４drｉvｅｒ．２９.howtｏcｏlｌecｔrｅquuiremenｔｓｆormurｃlieｎt．3０.ｗhichｐrocｅｓsuｓeｉｎuｒｐｒoject.３1．whａt(yī)isdeployｍentdesｃrｉｐtor．3２．whatisｈeirarchyoffilesinstrｕtｓ.33．pleaｓｅdrawstrｕtsframewrok．3４.pleａsｅdraｗｊ2eeaｒcｈｉｔecture．３5.ｐｌeａseｄｒａｗｍvc－2arcｈiteｃtuｒe.3６．pｌeａsedrawthathoｗdesiｇnopmｏduｌｅ.37.hｏwtofinｄａfileｏnｌｉnux.３８.hｏwｔocｏnfiguｒeweblogic8．1onｌinuｘ.39.whｙyouｕｓｅstrutsfｒamｅworkinuｒｐrｏjｅct.４0.whaｔiｓｐlａｔfromindｅpｅndenｔ41.whaｔisawｔaｎdｓwiｎg.42.whatisheaｖｙwieghtcomｐoｎｅnts．43.ｗhatisfeaｔureｏfweblｇoic8．１.44．ｗhｙyoｕchooseａppliｃaｔiｏnservｅrｏｎlinuｘandｄａｔａｂasesｅrvｅrｏnaiｘ.45.ｐleａｓetellmｅaｂouturｐrｏjｅct.46.whatiｓmａjorconceptｓinooｐs．47．whyuｃhooｓemvc-2arｃhitectｕｒｅ．48.whatｉsimpｌicitobject.4９.hｏｗｍａnyｉmpliciｔｏbjｅctsｉnｊsｐ50．ｗhｙchoosｅwｅｂｌｏｇic8．1oｔhertｈanaｎyａpplicａｔiｏnsｅｒver.51.ｗhatiswaterfallｍodelvssdlc5２．whatisuseofｄａｔaflｏｗdiａgrams5３.ｗhatisiｐｉnurproject.54．whataboutrｅcepｔioｎmｏdｕｌｅ—————————————————————————————————————————————————————————1.OraｃleiｓａnRDBMＳpｒodｕctwitｈDDLaｎdDMLfroｍａcompanycａlledOｒａcleＩｎc．２.Ｄiｆfｅrencebｅtwｅen8iaｎd9iiｓgivenintheOｒacｌesite3.Ｑueｓtionnotaｖailable4.Ｓｏｍｅtｈｉng５．oopsｉｓOｂjecｔOrieｎtｅdProｇrａmming6.whａt(yī)issiｎgleinheritanｃe.anｓ:ｏｎeｃlassｉsinheriｔｅdbｙonlyotｈeroneclａｓs７．whatisｍuｌtiｐleiｎheritancｅ.ａｎｓ:Onecｌaｓｓinherｉｔｉngmorethaｎoneclａｓｓaｔａt(yī)ｉｍe８.canjavａsupportmｕltiｐleiｎherｉｔance.ａｎs:No9.ｗhatiｓinｔerface.ans:Interｆaｃｅhａsonlyｍetｈｏｄdeclaraｔionsbutnｏdｅfn10．wｈatisdiｆfｅｒenecｂetｗeeｎａbstｒａctclaｓsaｎｄinｔerｆaｃe.ans：Inａbsｔｒactcｌassｓomemｅthodsmａycｏｎｔａindeｆｉnition，butiniｎterfaｃeeverymethｏｄsｈouldbeａｂｓtract11.howtｏuproｖeｔhatabsｔrａcｅclasscａｎnotiｎstantiateｄｉreｃｔly．a(chǎn)ｎｓ:Astｈｅydoｎthaｖecｏｎstrｕctorthｅycanｔbeｉnstaｎｔｉaｔed12．ｗhaｔisdｉffｅreｎeｃebetweensｔｒingａndsｔｒｉngbuｆfer.aｎs:Strｉngsareiｍmutａbｌewｈereａｓstriｎgbuffercanｂemodｉｆied13.whatisimmutabｌeaｎｓ：Whｉchcanｔbeｃhａngｅd１4.howtowriteaｐrogｒaｍｕsinｇsortprogram.15ｈowｔｏwrｉtｅａprｏgraｍusｉngunsortprogram．a(chǎn)ns:BｏtｈcanbedoneuｓinｇjavascripｔＴhisiｓforＳoｒtfｕnctionSelectTexｔＳｏrt(obj)｛//sorｔｂytextvａrN=oｂｊ.optioｎs.lengｔh;ｆoｒ(vaｒi=0;i＜N-1;i++){fｏr(varj=i＋１;j＜N;ｊ+＋）{if(obj.optioｎs［i].text＞obj.ｏptions［j].teｘt)｛vari1=(ｏｂj.ｏptioｎｓ[i].ｓelｅｃｔed==ｔrue）?tｒｕe：falsevａｒj1=(obj.oｐｔioｎs[j].ｓeleｃted＝=true)？ｔrｕe：falsevａrq1=obｊ.optioｎs[j］.ｔｅxt;varq2=obj.opｔioｎs[j].value；ｏbj.optiｏnｓ[j].text=obj.ｏptions[i].texｔ;obj.opｔions［ｊ].vａｌuｅ=ｏbｊ.optｉonｓ[ｉ].vａｌue;obj.options[i］．teｘt＝q1;obｊ.ｏptions[ｉ].ｖalue＝q2;obj．oｐtiｏｎｓ[i].sｅlectｅd=(j1&&tｒue)？true：faｌseｏbｊ.ｏｐtioｎｓ［j].sｅｌected=(i1＆&ｔｒue)?true:falsｅ}｝}ｒｅturnｔrue｝16．ｗhatｉslｅgａｃy.17．whatisｌｅgacyａpi18．ｗｈatisleｇａcyｉnterfacｅ．a(chǎn)ns:legacｙiｓsomeｔｈinｇthatisoldｉntermsoftechnology/system19.whatismaｉndｉfferencehasｈmapaｎdhａstabｌeans:Hashtａbleisｓｙnchroｎiｓed20．wｈaｔismaｉndiffｅrencｅbｅtwｅenａrraylisｔandｖector.ans：Veｃｔorisｓｙnchroniｓed21．whaｔｉsｓtrutsframeｗoｒk.２2.whａｔarｅdisｔriｂｕtedｔeｃhｏnolｏgies．dｉstrｉbｕｔｅdtechnologiesmeansanｙtechnoｌｏgy/ｓ/wprogrａmtｈataｒeｈａviｎgｍaｎycoｍpoｎeｎtsinmｕlｔipｌeenvironmeｎtsthatｉｎｔeractwｉtheachotherｄepenｄinｇoｎthefuｎctionalｒeqｕiｒementsanｄdesiｇｎ.23．ｗhaｔｉｓadvantａgeanddｉｓadvａnｔagｅofdistrｉbutedtecｈonologｉｅs.ｏvｅｒｄependａnｃｅｏnsinglｅｐｌatform/singlｅlanｇuageｉsavoided.Appliｃatｉoncanbebuｉｌtfｌｅxiｂlｅｔoｍｅetrequｉreｍents.Diｖｉsionｏｆlａbouriｓpoｓsiblｅ.Bｅstofａllｔｈetechnologiesandpｌaｔfｏrmscanbeoptiｍallｙｕｔilｉzeｄ．Compｌexｉtyofｒeｑｕirementscanbereduceｄ．25.wｈatisdiｆfeｒｅncebetweenprｏｃedurｅandfｕnctions.'ａns:Fuctionscａｎrｅtｕrnvalue,procｅdｕreｓｃanｔrｅtｕrnvａlue26．wｈaｔisｊdｂｃ.aｎs:CoｎｎectｉngtoDBｆrｏｍjavaproｇramreqｕirｅｓＪDBC27．whataretｙpeｏfdrivers.tyｐｅ１,2,3,429.howtoｃｏlleｃｔrｅquuirｅmｅｎtsｆorｍuｒcｌｉent.isnotａjobofatechnicaｌperson.ＩtｉsbettｅrfoｒaＢＡtodoit．30．wｈichproｃｅssｕseｉnurproｊeｃｔ.Geｎｅｒallｙｕｃaｎsay：Ｐroｊｅctｒeｌatedprocess：Ａｎaｌysis,Ｄｅｓign,Sｉｇn－ｏfｆＤocumentｓ,Ｉmpｌemenｔation,Integration,Tesｔinｇ，UATWｏｒｋｒelatedproｃeｓｓ：TechniｃalＤｅsｉgn,ＷorkAllｏcatiｏｎ,CoｄeＲeviewCheckｌist,UniｔTestＦoｒmwｉllbepｒepaｒeｄｂｙtｈePｒojeｃtＬeadandgiｖeｎtoｔhedevelopｅr．Ｄｅveloperprepａr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AＪavaappleｔismaｄeupoｆatｌeastoneｐublicｃlaｓstｈatｈａstｏbeｓｕbcｌasseｄfｒomjavａ.ａwt.Applｅt．Theaｐpｌｅtiｓcoｎfinｅdｔoliｖinginｔｈｅuser'ｓWeｂbrｏwser,anｄthebrowｓer'ssｅｃuｒiｔyrules,(orSun'sａpｐletvieweｒ,ｗｈiｃhhasｆｅwerresｔrictions)．?Thedｉffereｎcesbeｔweenanaｐｐｌetanｄａnaｐplicaｔｉｏnaｒｅasfollowｓ:1.ApplｅｔscanｂeeｍbeddediｎＨTＭLpagesaｎddownloadｅdovｅrｔheInteｒnetwhｅrｅasApｐliｃatｉｏｎshaveｎｏspeｃialsｕpportinHTMLforemｂeｄdｉngorｄoｗnloading.2．Applｅtscanonlｙbｅeｘecuｔedinsidｅａjａvａcompatiｂlecontaiｎer,suchasabroｗserorapplｅｔviｅwerｗhｅｒeａsApplicatｉonsareeｘecutedaｔｃommandlineｂｙｊava．exeorjview.exe.3.Appletsｅｘecuｔeuｎdｅrstrictsecuｒitylimiｔatｉonsthａt(yī)diｓalｌowｃerｔainｏperatioｎｓ（sandboｘmodｅlsｅcuritｙ)wｈｅrｅａｓAｐplｉcａt(yī)ionshaｖeｎoｉnhｅrｅnｔsｅcｕｒityrestriｃｔions.4.Appletsｄon＇ｔｈaveｔhemain()methodａｓｉnａpｐlicatｉons.Ｉnstｅaｄtｈｅｙopeｒateｏnanenｔiｒeｌydｉffｅrentmｅchaｎismwｈerｅtheyareiniｔialｉｚedbyinit(),sｔartedbystart(),stoｐpedbystｏp()ordeｓtroyedbｙdestroy()．２.Whａt(yī)aｒｅjavabeａｎs?

JavａBeansisａpoｒtａble,platform-independentcompｏnｅｎtmodelwrｉtｔeninｔheJａvaprograｍminglanguage，dｅｖeｌoｐeｄｉnｃollaborationwithinｄusｔryｌeａders.Ｉｔｅnablesdevｅｌoperｓｔowritｅrｅusablecomponentsｏnｃeandruｎｔｈemanywhere--benefiｔingｆrｏｍthｅｐlaｔform-indepｅndentpowerofJavａt(yī)ｅｃhnoｌogy．JavａBｅansａcｔｓａsaＢridgｅbetｗeenpｒoprietarycoｍｐonentｍodelｓandｐrｏvidesasｅamｌessａndpｏweｒfｕｌｍｅansfｏrｄeveｌｏperstobｕiｌdcompｏneｎtｓtｈａt(yī)runinAcｔiveXcｏｎｔainｅｒａｐplicａt(yī)ionｓ．?Javaｂeａnsｉsverypｏwｅrfｕltoolyoucａnuseｉnｙoｕrservｌeｔ／JＳPｂrｉｄｇe.YoucａnuｓetｈeｓeｒvlｅtstoｂｕｉldtｈｅbeanａndcａnｂｅpassedoｖeｒtotheJSPforｒｅaｄing.ＴhisｐrｏvｉdeｓtightｅncapsｕｌationｏｆｔheｄataｗhileｐｒesｅｒvingthesａnctityoｆservｌeｔｓandJSP.3．ＷhａｔisRＭＩ？

ＲMIstaｎｄsfoｒRemoteＭethodＩnvoｃａt(yī)ioｎ.Ｔｒaｄiｔｉoｎalapproacheｓtoexecutingｃｏdeoｎｏｔhermacｈｉnesacroｓsａnetｗoｒkhavebeｅnconfｕsingasｗｅｌlastedｉoｕsandｅrｒor－proｎｅtoiｍｐleｍent.Thenicｅstwａｙtothinkａboｕtthisｐｒoblｅｍｉｓｔhaｔsomｅobjecｔｈａppenｓtｏliveonanothｅrmａchine,ａndthatyｏucａnｓendaｍｅssaｇetoｔheremoteｏbｊｅｃtａndｇｅtarｅｓuｌtａsiｆｔｈeobｊecｔｌiｖedoｎｙouｒloｃalｍacｈine.