LTPJ-Chapter02.ppt

LearnToProgramJava 1 Chapter02 BasicBuildingBlocks LearnToProgramJava 2 BasicBuildingBlocks Words numbers punctuationmarksandspecialsymbolsformthebasicbuildingblocksoftheEnglishlanguage Javatoohasitsownsetofbuildingblocksandrules VocabularyandcharactersetsPrimitivedatatypesIdentifiersReservedwordsComments LearnToProgramJava 3 Vocabularyandcharactersets MorninggoodTanMr GoodmorningMr Tan Javavocabularyismadeupofletters digitsandspecialsymbols suchas etc GroupedtogetherfollowingthesyntaxrulesofJava LearnToProgramJava 4 ASimpleJavaProgram classChap2Print2Numbers publicstaticvoidmain Stringargs Comment prints2numbers intfirstNumber 5 intsecondNumber 10 System out println The1stnumberis firstNumber System out println The2ndnumberis secondNumber Theoutputoftheaboutcodeis The1stnumberis5The2ndnumberis10 LearnToProgramJava 5 Variables Anamedstoragelocationinthecomputer smemorythatstoresavalueofaparticulartypeforusebyprogram Exampleofvariabledeclaration DataTypevariableName intmyAge cellPhone doublesalary chartempChar Thedatatypecaneitherbebuilt inprimitivetypes e g int double char objectclasses orreferencedatatypes e g String BufferedReader LearnToProgramJava 6 PrimitiveDataType Datatypesthathavebeenpre definedinJava LearnToProgramJava 7 PrimitiveDataType boolean trueorfalse example booleanisStart true booleanisEnd false char charactersexample chartempChar1 A chartempChar2 chartempChar3 refertotable2 2 page24fortheescapedcharacters LearnToProgramJava 8 PrimitiveDataType int integers octal decimalorhexadecimal example intnum1 036 octal base8intnum2 30 decimal base10intnum3 0 x1E hexadecimal base16Octal 0 1 2 3 4 5 6 7Decimal 0 1 2 3 4 5 6 7 8 9Hexadecimal 0 1 2 3 4 5 6 7 8 9 A B C D E F LearnToProgramJava 9 PrimitiveDataType float decimalnumberwithanoptionaldecimalpointandfollowedbyanoptionalexponent example floatdec1 15 floatdec2 15 5f floatdec3 3 5E2f double decimalnumberwithanoptionaldecimalpointandfollowedbyanoptionalexponent example doubledec1 15 doubledec2 15 5 doubledec3 1E2 LearnToProgramJava 10 ReferenceDataType conceptofobjectsinChapter6 null representsaninvalidoruncreatedobject AllescapesequencesthatareapplicabletocharacterscanbeembeddedwithinStringliterals LearnToProgramJava 11 DataType Datatype PrimitiveDatatype ReferenceDatatype byte int short long float double char boolean class interface array LearnToProgramJava 12 PrimitiveDataType Integer MAX VALUEInteger MIN VALUEFloat MAX VALUEFloat MIN VALUEDouble MAX VALUEDouble MIN VALUEShort MAX VALUEShort MIN VALUEByte MAX VALUEByte MIN VALUE LearnToProgramJava 13 publicclassJavaDemo01 publicstaticvoidmain Stringargs booleanflag true flag false inlanguageC 0 falseotherstrueflag 1 System out println flag LearnToProgramJava 14 publicclassJavaDemo02 publicstaticvoidmain Stringargs charc A inti c System out println i LearnToProgramJava 15 Identifiers Declaredentities suchasvariables methodandclass andlabelsarenamedbyidentifiers IdentifierinJavamustbeginwithaletter underscore ordollarsign followedbyanynumberofletters digits underscore anddollarsign Javaiscase sensitive tcsisnotTcsandisnotTCSNamingConvention Classname firstletteriscapitalize Variablename ifidentifierismade upofseveralwords firstwordisinlowercaseandtherestsareinitialcapitalized E g thisIsALongVariableName LearnToProgramJava 16 Identifiers Whichofthefollowingarevalididentifiers HelloWorld temp Str1Dollarabc123a b Valid Valid Valid Invalid cannotstartwithadigit Valid Invalid illegalcharacter LearnToProgramJava 17 ReservedWord Reservedwordscannotbeusedasidentifiers refertotable2 5page22 SinceJavaiscase sensitive AbstractcanbeconsideredasidentifierssinceabstractisnotequivalenttoAbstract Suchuseofidentifiernamescanbeconfusingandmayobscuretheintentionofthecode hencenotadvisable AllthereservedwordinJavaisinlowercase Althoughgoto validbutnotadvisable LearnToProgramJava 18 LearnToProgramJava 19 Comments Goodpracticetowritecommentstodescribethepurposeandalgorithmofapieceofcode CommentsareignoredbytheJVMatrun timeSinglelinecomment Multi linecomment JavaDoccomment Multi linecommentcannotbenested classnestedComments publicstaticvoidmain Stringargs somecomment System out println hello LearnToProgramJava 20 BasicProgramStructure Aprogramtoprintouttwonumbers classChap2Print2Numbers publicstaticvoidmain Stringargs intfirstNumber 5 intsecondNumber 10 System out println The1stnumberis firstNumber System out println The2ndnumberis secondNumber endmain endChap2Print2Numbers LearnToProgramJava 21 JavaDoc Example importjava math RoundingMode publicclasstestjavadoc publicstaticvoidmain Stringargs System out println testjavadoc Validatesachessmove Use link doMove int int int int tomoveapiece paramtheFromFilefilefromwhichapieceisbeingmoved paramtheFromRankrankfromwhichapieceisbeingmoved paramtheToFilefiletowhichapieceisbeingmoved paramtheToRankranktowhichapieceisbeingmoved returntrueifthemoveisvalid otherwisefalse publicbooleanisValidMove inttheFromFile inttheFromRank inttheToFile inttheToRank returntrue Movesachesspiece seejava math RoundingMode publicbooleandoMove inttheFromFile inttheFromRank inttheToFile inttheToRank returnfalse LearnToProgramJava 22 Summary VocabularyandCharacterSe