Java英文面试题

英文Javatm试题Question:Whatistransientvariable?Answer:Transientvariable臼n'tbeserialize.ForexampleifavariableisdeclaredastransientinaSerializablec1assandthec1assiswrittentoanObjectStream，thevalueofthevariablecan'tbewn忧entothestreaminsteadwhenthec1assisretrievedfromtheObjectStreamthevalueofthevariablebecomesnullQuestion:NamethecontainerswhichusesBorderLayoutastheirdefaultlayout?Answer:ContainerswhichusesBorderLayoutastheirdefaultare:window，FrameandDialogc1asses.Question:WhatdoyouunderstandbySynchronization?Answer:Synchronizationisaprocessofcontrollingtheaccessofsharedresourcesbythemultiplethreadsinsuchamannerthatonlyonethreadcanaccessoneresourceatatime.Innonsynchronizedmultithreadedapplication，itispossibleforonethreadtomodifyasharedobjectwhileanotherthreadisintheprocessofusingorupdatingtheobject'svalue.SynchronizationpreventssuchtypeofdatacorruptionE.g.Synchronizingafunction:publicsynchronizedvoidMethodl0{jjAppropriatemethod-relatedcode.E.g.Synchronizingablockofcodeinsideafunction:publicmyFunctionO{synchronized(this){jjSynchronizedcodehere.Question:WhatisCollectionAPI?Answer:TheCollectionAPIisasetofc1assesandinterfacesthatsupportoperationoncollectionsofobjects.Theseclassesandinterfacesaremoreflexi.ble，morepowerfu，lthevectors，arrays，andhashtablesife仔'ectivelyreplaces.andmoreregularthanExampleofc1asses:HashSet，HashMap，ArrayList，LinkedList，TreeSetandTreeMap.Exampleofinterfaces:Collection，5时，ListandMap.Question:IsIteratoraClassorInterface?Whatisitsuse?Answer:IteratorisaninterfacewhichisusedtostepthroughtheelementsofaCollection.Question:WhatissimilaritiesjdifferencebetweenanAbstractc1assandInterface?Answer:Differencesareasfollows:Interfacesprovideaformofmultipleinheritance.AclasscanextendonlyoneotherclassInterfacesarelimitedtopublicmethodsandconstantswithnoimplementation.Abstractclassescanhaveapartialimplementation，protectedparts，staticmethods，etc.AClassmayimplementseveralinterfaces.Butincaseofabstractclass，aclassmayextendonlyoneabstractclass.Interfacesareslowasitrequiresextraindirectiontofindcorrespondingmethodintheactualclass.Abstractclassesarefast.Similarities:NeitherAbstractclassesorInterfacecanbeinstantiated.Question:HowtodefineanAbstractclass?Answer:AclasscontainingabstractmethodiscalledAbstractclass.AnAbstractclasscan'tbeinstantiated.ExampleofAbstractclass:abstractclasstestAbstractClass{protectedStringmyString;publicStringgetMγStringO{returnmyString;publicabstractstringanyAbstractFunctionO;Question:HowtodefineanInterface?Answer:InJavaInterfacedefinesthemethodsbutdoesnotimplementthem.Interfacecanincludeconstants.AclassthatimplementstheinterfacesisboundtoimplementallthemethodsdefinedinInterface.EmapleofInterface:publicinterfacesamplelnterface{publicvoidfunctionOneO;publiclongCONSTANT_ONE=1000;Question:ExplaintheuserdefinedExceptions?Answer:UserdefinedExceptionsaretheseparateExceptionclassesdefinedbytheuserforspecificpurposed.Anuserdefinedcancreatedbysimplysub-classingittotheExceptionclass.Thisallowscustomexceptionstobegenerated(usingthrow)andcaughtinthesamewayasnormalexceptions.Example:classmyCustomExceptionextendsException{//TheclasssimplyhastoexisttobeanexceptionQuestion:ExplainthenewFeaturesofJDBC2.0CoreAPI?Answer:TheJDBC2.0APIincludesthecompleteJDBCAPI，whichincludesbothcoreandOptionalPackageAPI，andprovidesinductrial-strengthdatabasecomputingcapabilitiesNewFeaturesinJDBC2.0CoreAPI:Scrollableresultsets-usingnewmethodsintheResultSetinterfaceallowsprogrammaticallymovethetoparticularrowortoapositionrelativetoitscurrentpositionJDBC2.0CoreAPIprovidestheBatchUpdatesfunctionalitytothejavaapplicationsJavaapplicationscannowusetheResultSet.updateXXXmethods.Newdatatypes-interfacesmappingtheSQL3datatypesCustommappingofuser-definedtypes(UTDs)Miscellaneousfeatures，includingperformancehints，theuseofcharacterstreams，fullprecisionforjava.math.BigDecimalvalues，additionalsecurity，andsupportfortimezonesindate，time，andtimestampvalues.Question:Explaingarbagecollection?Answer:GarbagecollectionisoneofthemostimportantfeatureofJava.GarbagecollectionisalsocalledautomaticmemorymanagementasJVMautomaticallyremovestheunusedvariables/objects(valueisnull)fromthememory.Userprogramcann'tdirectlyfreetheobjectfrommemory，insteaditisthejobofthegarbagecollectortoautomaticallyfreetheobjectsthatarenolongerreferencedbyaprogram.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:DescribetheprinciplesofOOPSAnswer:TherearethreemainprincipalsofoopswhicharecalledPolymorphism，InheritanceandQuestion:ExplaintheEncapsulationprinciple.Answer:Encapsulationisaprocessofbindingorwr