02-JavaFundamentals

A and a are different which letters represent valid

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Unformatted text preview: t with underscore or dollar sign: _ $ • Java is case sensitive. A and a are different Which letters represent valid identifiers? a) b) c) abc m/h main d) e) f) $$$ 25or6to4 1_time i) j) k) a_1 student Number String Reserved Identifiers (keywords) A keyword is an identifier with a pre-defined meaning that can't be changed it's reserved double int Other Java reserved identifiers not a complete list boolean break case catch char class default do double else extends float for if import instanceOf int long new private public return void while Literals -- Java has 6 Floating-point literals 1.234 -12.5 1.2 3. .4 1e10 String literals "characters between double quotes" "'10" Integer literals (Integer.MIN and Ineger.MAX are shown) -1 0 1 -2147483648 2147483647 Boolean literals (there are only two) true false Null (there is only one) null Character literals 'A' 'b' '\n' '1' '' 0.1e-5 "_" Comments • • • • Provide internal documentation to explain program Provide external documentation with javadoc Helps programmers understand code--including their own There are three type of comments // on one line, or /* between slash star and star slash you can mash lines down real far, or */ /** * javadoc comments for external documentation * @return The square root of x */ public static double sqrt(double x) General Forms The book uses general forms to introduce parts of the Java programming language General forms provide information to create syntactically correct programs • Anything in yellow boldface must be written exactly as shown (println for example) • Anything in italic represents something that must be supplied by the user • The italicized portions are defined elsewhere Output Statements A statement, made up of tokens, is code that causes something to happen while the program runs General Forms for three output statements System.out.print( expression ); System.out.println(); System.out.println( expression ); Example Java code that writes text to the console System....
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