COMP 14 Introduction to ProgrammingReview ExerciseToday in COMP 14Reading Check-UpIntroductionSample Java ProgramProgramming LanguagesSpecial SymbolsWord Symbols aka reserved words, or keywordsIdentifiersIllegal IdentifiersQuestionsPrimitive Data Types What’s A Data Type?Primitive Data TypesPrimitive Data Types Numeric TypesIntegersPrimitive Data Types CharactersPrimitive Data Types BooleansArithmetic ExpressionsDivision and RemainderUnary vs. Binary OperatorsOperator PrecedenceSlide 23Integral ExpressionsFloating-point ExpressionsMixed ExpressionsType Conversion (Casting)Questions Evaluate These ExpressionsThe class StringStringsParsing Numeric StringsSlide 32SummarySlide 34To doTomorrowCOMP 14Introduction to ProgrammingMiguel A. OtaduyMay 13, 2004Review Exercise•Execution of c=2*a+b in a computerToday in COMP 14•Java–special symbols–identifiers–data types–operators–expressions–StringsReading Check-Up1. The rules of a language determine which instructions are valid.2. True or False? Hello! is an example of a legal Java identifier.3. If an operator has an integer and a floating-point operand, the result of the operation is a number.4. The expression (int) (9.2) evaluates to syntaxFalsefloating-point9Introduction•Computer program: a sequence of statements whose objective is to accomplish a task •Programming: process of planning and creating a program•Programming language: a set of rules, symbols, and special wordsSample Java Programpublic class Hello {public static void main (String[] args){System.out.println ("Hi There!");}}Upon execution, this program would displayHi There!Programming Languages•Programming languages have rules of grammar just as English does•syntax rules - which statements are legal and which are not•semantic rules - determine the meaning of the instructions•token - smallest individual unit of a program–special symbols–word symbols–identifiersSpecial Symbols+ - * /. ; ? ,<= != == >=Word Symbolsaka reserved words, or keywords•int•float•double•char•void•public•static•throws •return• reserved words are always all lowercase• each word symbol is considered to be a single symbol• cannot be used for anything other than their intendedpurpose in a program• shown in blue typewriter font in textbook• full table in Appendix AIdentifiers•Names of things (variables, constants, methods) in your programs•Can be composed of any combination of letters, digits, underscore (_), and dollar sign ($) •Cannot begin with a digit•May be any length•Java is case-sensitive–Total, total, and TOTAL are different identifiersIllegal IdentifiersQuestionsClassify the following as legal or illegal identifiers:1. My First Program2. my1stProgram3. 1stProgram4. $money5. an_identifier6. Jane'sProgramillegallegalillegallegallegalillegalPrimitive Data TypesWhat’s A Data Type?•A set of values and the operations that can be performed on those values•Primitive data are fundamental values such as numbers and characters•Operations are performed on primitive types using built-in operatorsPrimitive Data Types•8 primitive data types in Java–4 represent integers•byte, short, int, long–2 represent floating point numbers•float, double–1 represents characters•char–1 represents boolean values •booleanPrimitive Data TypesNumeric Types•The difference between the various numeric primitive types is their size, and therefore the values they can store:TypebyteshortintlongfloatdoubleStorage8 bits16 bits32 bits64 bits32 bits64 bitsMin Value-128-32,768-2,147,483,648< -9 x 1018+/- 3.4 x 1038 with 7 significant digits+/- 1.7 x 10308 with 15 significant digitsMax Value12732,7672,147,483,647> 9 x 1018Integers•Examples: -6728, -67, 0, 78, 36782•Positive integers do not have a '+' sign in front of them (but they can)•No commas are used in an integer–commas in Java are used to separate items in a listPrimitive Data TypesCharacters•A char stores a single character from the Unicode character set–an ordered list of characters, and each character corresponds to a unique number–uses 16 bits per character, allowing for 65,536 unique characters•Character literals are delimited by single quotes:'a' 'X' '7' ' ' '$' ',' '\n'newline character(we'll discuss later)Primitive Data TypesBooleans•Only two valid values–true or false–uses 1 bit for storage•Represent any situation that has 2 states–on - off–true - false•true and false are reserved words•Expression - a combination of one or more operands and their operators•Arithmetic expressions compute numeric results and make use of the arithmetic operators:•If either or both operands associated with an arithmetic operator are floating point, the result is a floating pointAddition +Subtraction -Multiplication *Division /Remainder %Arithmetic Expressions•If both operands to the division operator (/) are integers, the result is an integer (the fractional part is discarded)•The remainder, or modulus, operator (%) returns the remainder after dividing the second operand into the first (only works with integer types)14 / 3 equals?8 / 12 equals?4014 % 3 equals?8 % 12 equals?28Division and RemainderUnary vs. Binary Operators•Unary operators–has only one operand–example: - (negative, not subtraction)-5•Binary operators–has two operands–example: - (subtraction)5 - 3Operator Precedence•Determines the order in which operators are evaluated:1. multiplication, division, and remainder 2. addition, subtraction, and string concatenation3. arithmetic operators with the same precedence are evaluated from left to right•Parentheses can be used to force the evaluation order (just like in math)Operator Precedence•What is the order of evaluation in the following expressions?a + b + c + d + e1 432a + b * c - d / e3 241a / (b + c) - d % e2 341a / (b * (c + (d - e)))4 123Integral Expressions•All operands are integers•Result is an integer•Examples:2 + 3 * 53 + x – y / 7x + 2 * (y – z) + 18Floating-point Expressions•All operands are floating-point numbers•Result is a floating-point•Examples:12.8 * 17.5 – 34.50x * 10.5 + y - 16.2 7.0 / 3.5Mixed Expressions•Operands of different types•Examples:2 + 3.56 / 4 + 3.9•Integer operands yield an integer result•Floating-point operands yield a floating-point result•If both types of operands are present, the result is a floating-point number–implicit type coercion•Precedence rules