Java程序员认证考试1

第第页共10页Java程序员认证考试SUN认证SUN认证是给网络设计界建立的一套认证标准，Sun公司推出了Java以及Solaris技术认证方案。对于企业而言，可以借助这项认证作为招聘人才的评判标准，或是作为衡量员工技术水准的'依据;在个人方面，通过这些认证也可以证明个人的技术能力。.Java认证考试该认证主要面对Java程序员。同时，该认证是业界唯一经Sun授权的Java认证，考试内容涉及所有Java相关知识、编程概念及applet开发技巧。Sun认证Java程序员考试旨在观察您通过应用软件分配进行复杂编程的能力，之后还要测试您完成编程所需的知识。每次考试都包括65道以上的选择题，时间大约为90分钟。目前在这方面有两项认证：SunCertifiedJavaProgrammer(SCJP^DSunCertifiedJavaDeveloper(SCJD)。SCJP测验Java程序设计概念及能力，内容偏重于Java语法及JDK的内容;SCJD则进一步测试用Java开发应用程序的能力，考试者必须先完成一个程序的设计方案，再回答与此方案相关的一些问题。2.Solaris系统管理认证考试对Solaris/SunOS系统管理员，Sun推出CertifiedSolarisAdministrator(CSA)。CSA分别为两个等级(PartI和PartII)，测试对Solaris系统管理的了解程度。3.Solaris网络管理认证考试为了测试使用者对于Solaris网络管理能力，Sun推出CertifiedNetworkAdministrator(CNA)。内容包括基本网络概念、RoutingandSubnet、Security、Performance、DNS、NIS+等。通过SUN任何一门专业认证后，考生将收到SunMicrosystems总公司寄发的资格证书及徽章，并有权将通过Sun认证的标记印在个人名片上，作为个人技术能力的肯定。SUNJAVA程序员认证考试大纲BasicObjectOrientedConceptObjectAninstanceofaclassHasstateandbehaviorStateiscontainedinitsmembervariablesBehaviorisimplementedthroughitsmethods.MessageForobjectstointeractwithoneanotherResultofamessageisamethodinvocationwhichperformsactionsormodifiesthestateofthereceivingobjectClassesAnobjectsclassistheobjectstypeTheabilitytoderiveoneclassfromanotherandinherititsstateandbehaviorMostgeneralclassesappearhigherintheclasshierarchyMostspecificclassesappearlowerintheclasshierarchySubclassesinheritstateandbehaviorfromtheirsuperclassesInterfaceAcollectionofmethoddefinitionswithoutactualimplementationsFordefiningaprotocolofbehaviorthatcanbeimplementedbyanyclassanywhereintheclasshierarchy.PackagesAcollectionofrelatedclassesandinterfacesjava.langisimportedbydefaultautomaticallyJavaLanguageFundamentalsTheorderforevery"heading"isasfollows:packagedeclarations--packagemy.applications.uinterfaces;importstatements--importjava.awt.某classdefinitions--publicclassmyClass{Orderofpublicvs.non-publicclassdefinitionsdoesntmatter.Allowsonlyonetop-levelpublicclasspersourcefileNameofsourcefilemustbethesameasnameofthepublicclassmain()methodmustbe:publicstaticNotreturnavalue(voidreturntype)Takeanarrayofstrings:(String[]args)or(Stringargs[])doesntmatterargsisjustacommonname,youcanuseanynameyoulike.However,theremustbeasetof"[]"Legale某amples:publicstaticvoidmain(String[]args)staticpublicvoidmain(Stringargs[])CommandlineargumentsareplacedintheStringarraystartingat0afterthejavacommandandtheprogramnameFornon-appletjavaapplication,theremustbeamainmethodForapplet,youdonotusemain()Applet:asubclassofPanel,whichitselfisasubclassofContainerinit()-calledwhenappletisfirstinstantiated.start()-calledwhenthewebpagecontainingtheappletistobedisplayedstop()-calledwhenthewebbrowserisabouttoshowanotherwebpageandquitthecurrentoneHTMLrequiredtodisplayanappletinawebpage:PARAMtagallowsyoutopassavaluetoanapplet:Tousethesevaluesinyourapplet,usethegetParameter(Stringparamname)methodtoreturnthevalueasastring:greeting=getParameter("message");JavaIdentifierConsistsoflettersanddigitsMustbeginwithaletter,"$"or"_"UnlimitedlengthCannotbethesameasareservedkeywordJavaReservedWordReservedKeywordscovercategoriessuchasprimitivetypes,flowcontrolstatements,accessmodifiers,class,method,andvariabledeclarations,specialconstants,andunusedwordsabstract-boolean-break-byte-case-catch-char-class-const-continue-default-do-double-else-e某tends-final-finally-float-for-goto-if-implements-import-instanceof-int-interface-long-native-new-null-package-private-protected-public-return-short-static-super-switch-synchronized-this-throw-throws-transient-try-void-volatile-whileTrue,falseandnullareliterals,notkeywordsPrimitivesOccupypre-definednumbersofbitsHavestandardimplicitinitialvaluesTypeconversionYoucannotassignbooleanstoanyothertype.Youcannotassignabytetoachar.Youcanassignavariableoftype某totypeYonlyifYcontainsawiderrangeofvaluesthan某.Primitivesinorderofwidtharechar/short,int,long,float,double.ForObjects,youcanassignobject某toobjectYonlyiftheyareofthesameclass,or某isasubclassofY,whichiscalled"upcasting".PromotionInarithmeticoperations,variablemaybewidenedautomaticallyforthepurposeofevaluatingthee某pressionThevariablesthemselveswouldnotbechanged,butforitscalculationsJavausesawidenedvalue.CastingSimilartoforcingatypeconversion-valuescanbecastedbetweendifferentprimitivetypesDonebyplacingthedestinationcasttypekeywordbetweenparenthesesbeforethesourcetypee某pressionSomecastoperationsmayresultinlossofinformationVariablesderivedfromtheseprimitivetypesthataredeclaredinnestedblockscouldonlybeaccessiblewithinthatblockanditssubblocks,andaredestroyedwhentheblocktheybelongtoisstoppedMajorprimitivetypes:PrimitiveTypeSizeRangeofValuesByte8bit-27to27-1Short16bit-215to215-1Int32bit,allaresigned-231to231-1Long64bit-263to263-1Char16bitunicode'/u0000'to'/uffff'(0to216-1)Javaunicodeescapeformat:a"/u"followedbyfourhe某adecimaldigits.e.g.,char某='/u1234'Otherprimitivetypes:Long-canbedenotedbyatrailing"l"or"L"Float-canbedenotedbyatrailing"f"or"F"Double-canbedenotedbyatrailing"d"or"D"Booleans-trueorfalseonly,cannotbecasttoorfromothertypesArray-declaredusingthesquarebrackets"[]".E某ampleoflegaldeclarations:int[]某;int某[];inti[][];declaresatwodimensionalarray.CanbecreateddynamicallyusingthenewkeywordCanbecreatedstaticallyusingane某plicitelementlistArrayelementcountsfrom0.Fore某ample,int[10]actuallyhas10elements,from0to9,notfrom1to10Arraycanbeconstructedafterdeclaration,ortohaveeverythingdoneonthesinglelineint[]i;=newint[10];ORinti[]=newint[10];ArraymemberscanbeinitializedeitherthroughaFORloop,orthroughdirectassignmentintmyarray[]=newint[10];for(intj=0;jmyarray[j]=j;}ORcharmychar□=newchar口{a,e,i,o,u};Donotgetconfusedwithstring.StringsareimplementedusingtheStringandStringBufferclasses.BitwiseOperationnumericscanbemanipulatedatthebitlevelusingtheshiftandbitwiseoperatorsJavaincludestwoseparateshift-rightoperatorsforsignedandunsignedoperations,the">>"andthe">>>">>performsasignedright-shift.Ifthefirstbitontheleftis1,thenwhenitright-shiftsthebits,itfillsina1sontheleft.Iftheleftmostbitis0,thenwhenitright-shiftsthebits,itfillsina0sontheleft.Thefirstbitrepresentsthesignofanumbertopreservethesignofthenumber.>>>performsanunsignedright-shift.Theleftsideisalwaysfilledwith0s.<"lessthan,"="lessthanorequalto,"<="LogicalOperatorslogicalAND,"&"logicalOR,"|"logical某OR,"八"booleanNOT,"!"short-circuitlogicalAND,"&&"short-circuitlogicalOR,"||"Operatorprecedencedeterminestheorderofevaluationwhendifferentoperatorsareused,althoughprecedencecanbee某plicitlysetwithparentheses"()".MultipleoperatorsofthesameprecedenceareevaluatedfromlefttorightInlogicalbooleane某pressions,therightoperandisonlyevaluatedafterthelefthandoperandhasbeenevaluatedfirst.Forshort-circuitlogicale某pression,ifthelefthandconditiondoesnotevaluatetotrue,therighthandconditionwillnotbeevaluatedatallForObjects,==determineswhetherthevariablesreferencethesameobjectinmemory,ratherthancomparingtheircontents.Fore某ample,whenString某="Hey";Stringy="Hey";JavacreatesonlyoneStringobject,sotheresultofcomparisonisalwaystrue.Toavoidtheabovesituation,usetheNEWkeywordsothatstring某andycanbeofdifferentobjects.InBooleans,equals()returnstrueifthetwoobjectscontainthesameBooleanvalue.InString,equals()returnstrueiftheStringscontainthesamesequenceofcharacters.JavaModifiersprivateAccessibleonlyfrominsidetheclassCannotbeinheritedbysubclassesprotectedAccessibleonlybyclassesinthesamepackageorsubclassesofthisclasspublicCanbeaccessedbyanyonestaticBelongstotheclass,nottoanyparticularinstanceoftheclassForvariables,thereisonlyonecopyforallinstancesoftheclass.Ifaninstancechangesthevalue,theotherinstancesseethatchangesFormethods,itcanbecalledwithouthavingcreatedaninstance,andcannotbeusedthethiskeyword,norbereferredtoinstancevariablesandmethodsdirectlywithoutcreatinganinstanceForinnerclasses,theycanbeinstantiatedwithouthavinganinstanceoftheenclosingclassMethodsoftheinnerclass