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1、最近在网上闲逛时偶然发现此文章,基本上指出了SCJP的出题陷阱,读过后觉得其列的还比较详细,故贴与此,希望能对打算考SCJP的朋友有一些帮助.此文虽是E文,但句法简单,很容易理解,而且我在大部分后面加了一些注释"()",对新手可能会有帮助.SCJP考题中的陷阱原著AjithKallambella(1)Twopublicclassesinthesamefile.(illegal)(2)Mainmethodcallinganon-staticmethod.(illegal)(3)Methodswiththesamenameasthecons
2、tructor(s).(这种题常有)(4)Threadinitiationwithclassesthatdonothavearun()method.(常考之题)(5)Localinnerclassestryingtoaccessnon-finalvars.(illegal)(6)Casestatementswithvaluesoutofpermissiblerange.(byte,int,short,chat)(7)Mathclassbeinganoptionforimmutableclasses!!(totallywrong!)(8)
3、instanceOfisnotsameasinstanceof.(9)Privateconstructors.(legal)(10)Anassignmentstatementwhichlookslikeacomparison.(比如说if(a=true),对于这种题眼睛亮一点)(11)System.exit()intry-catch-finallyblocks.(finally不会执行)(12)Orderoftry-catch-finallyblocksmatters.(若顺序错的话:error:Notrybeforecatch)(13
4、)main()canbedeclaredfinal.(OK)(14)-0.0==0.0istrue.(15)Aclasswithoutabstractmethodscanstillbedeclaredabstract.(16)RandomAccessFiledescendsfromObjectandimplementsDataInputandDataOutput.(17)MapdoesnotimplementCollection.(18)Dictionaryisaclass,notaninterface.(19)Collectionis
5、anInterfacewhereasCollectionsisahelperclass.(这题我倒没见过,但还真容易看混)(20)Classdeclarationscancomeinanyorder.(也就是说:classChildextendsParents{}classParents{}这种顺序是可以的.)(21)Forwardreferencestovariablesgivescompilererror.(22)Multidimensionalarrayscanbesparce.(这句话是说:多维数组中子数组不一定必须有一定个数的
6、元素,比如我们把一个二维数组看成一个矩阵,那么行与列中的元素可以不完整,可以不对齐.)(23)Arrays,whetherlocalorclass-level,arealwaysinitialized.(24)Stringsareinitializedtonull,notemptystring.(25)AnemptystringisNOTthesameasanullstring.(26)Adeclarationcannotbelabelled.(27)"continue"mustbeinaloop(for,do,while).Itcan
7、notappearincaseconstructs.(28)Primitivearraytypescanneverbeassignedtoeachother,eventhoughtheprimitivesthemselvescanbeassigned.(也就是说:ArrayofLongPrimitives=ArrayofIntegerPrimitives会编译出错,但longvar=intvar是合法的)(29)Aconstructorcanthrowanyexception.(30)Initilializerblocksareexec
8、utedintheorderofdeclaration.(31)Instanceinitializer(s)getsexecutedONLYIFtheobjectsareconstructed.(32)Al
