developer.com - Reference Click here to support our advertisers SHOPPING JOB BANK CLASSIFIEDS DIRECTORIES REFERENCE Online Library LEARNING CENTER JOURNAL NEWS CENTRAL DOWNLOADS COMMUNITY CALENDAR ABOUT US Journal: Get the weekly email highlights from the most popular journal for developers! Current issue developer.com developerdirect.com htmlgoodies.com javagoodies.com jars.com intranetjournal.com javascripts.com All Categories : Java Appendix A Java Languague Summary by Laura Lemay and Michael Morrison CONTENTS Reserved Words Literals Variable Declaration Variable Assignment Operators Objects Arrays Loops and Conditionals Class Definitions Method and Constructor Definitions Importing Guarding This appendix contains a summary, or quick reference, for the Java language, as described in this book. Note This is not a grammar overview, nor is it a technical overview of the language itself. It's a quick reference to be used after you already know the basics of how the language works. If you need a technical description of the language, your best bet is to visit the Java Web site (http://java.sun.com) and download the actual specification, which includes a full BNF grammar. Language keywords and symbols are shown in a monospace font. Arguments and other parts to be substituted are in italic monospace. Optional parts are indicated by brackets (except in the array syntax section). If there are several options that are mutually exclusive, they are shown separated by pipes (|) like this: [ public | private | protected ] type varname Reserved Words The following words are reserved for use by the Java language itself (some of them are reserved but not currently used). You cannot use these terms to refer to classes, methods, or variable names: abstract do import public try boolean double instanceof return void break elseint short volatile byte extends interface static while case final longsuper   catch finally native switch   char float newsynchronized   class fornull this   const gotopackage throw   continue if private throws   default implements protected transient   Comments /* this is the format of a multiline comment */ // this is a single-line comment /** Javadoc comment */ Literals number Type int number[l | L] Type long 0xhex Hex integer 0Xhex Hex integer 0octal Octal integer [ number ].number Type double number[ f | f] Type float number[ d | D] Type double [ + | - ] number Signed numberenumber Exponent numberEnumber Exponent 'character' Single character "characters" String "" Empty string \b Backspace \t Tab \n Line feed \f Form feed \r Carriage return \" Double quote \' Single quote \\ Backslash \uNNNN Unicode escape (NNNN is hex) true Boolean false Boolean Variable Declaration [ byte | short | int | long ] varname Integer (pick one type) [ float | double ] varname Float (pick one type) char varname Character boolean varname Boolean classname varname Class type type varname, varname, varname Multiple variables The following options are available only for class and instance variables. Any of these options can be used with a variable declaration: [ static ] variableDeclaration Class variable [ final ] variableDeclaration Constants [ public | private | protected ] variableDeclaration Access control Variable Assignment variable = value Assignment variable++ Postfix Increment ++variable Prefix Increment variable---- Postfix Decrement --variable Prefix Decrement variable += value Add and assign variable -- = value Subtract and assign variable *= value Multiply and assign variable /= value Divide and assign variable %= value Modulus and assign variable &= value AND and assign variable | = value OR and assign variable ^= value XOR and assign variable <<= value Left-shift and assign variable >>= value Right-shift and assign variable <<<= value Zero-fill, right-shift, and assign Operators arg + arg Addition arg - arg Subtraction arg * arg Multiplication arg / arg Division arg % arg Modulus arg < arg Less than arg > arg Greater than arg <= arg Less than or equal to arg >= arg Greater than or equal to arg == arg Equal arg != arg Not equal arg && arg Logical AND arg || arg Logical OR ! arg Logical NOT arg & arg AND arg | arg OR arg ^ arg XOR arg << arg Left-shift arg >> arg Right-shift arg >>> arg Zero-fill right-shift ~ arg Complement (type)thing Casting arg instanceof class Instance of test ? trueOp : falseOp Tenary (if) operator Objects new class(); Create new instance new class(arg,arg,arg...) New instance with parameters object.variable Instance variable object.classvar Class variable Class.classvar Class variable object.method() Instance method (no args) object.method(arg,arg,arg...) Instance method object.classmethod() Class method (no args) object.classmethod(arg,arg,arg...) Class method Class.classmethod() Class method (no args) Class.classmethod(arg,arg,arg...) Class method Arrays Note The brackets in this section are parts of the array creation or access statements. They do not denote optional parts as they do in other parts of this appendix. Type varname[] Array variable type[] varname Array variable new type[numElements] New array object array[index] Element access array.length Length of array Loops and Conditionals if ( test) block Conditional if ( test ) block else block Conditional with else switch (test) {     case value : statements     case value : statements     ...     default : statement} switch (only with int or  char types) for (initializer; test; change ) block for loop while ( test ) block while loop do block while (test) do loop break [ label ] Break from loop or switch continue [ label ] Continue loop label: Labeled loops Class Definitions class classname block        Simple class definition Any of the following optional modifiers can be added to the class definition: [ final ] class classname block No subclasses [ abstract ] class classname block Cannot be instantiated [ public ] class classname block Accessible outside package class classname [ extends Superclass ] block Define superclass class classname [ implements interfaces ] block Implement one or more interfaces Method and Constructor Definitions The basic method looks like this, where returnType is a type name, a class name, or void: returnType methodName() block Basic method returnType methodName(parameter, parameter, ...) block Method with parameters Method parameters look like this: type parameterName Method variations can include any of the following optional keywords: [ abstract ] returnType methodName() block Abstract method [ static ] returnType methodName() block Class method [ native ] returnType methodName() block Native method [ final ] returnType methodName() block Final method [ synchronized ] returnType methodName() block Thread lock before executing [ public | private | protected ] returnType methodName() Access control Constructors look like this: classname() block Basic constructor classname(parameter, parameter, parameter...) block Constructor with parameters [ public | private | protected] classname() block Access control In the method/constructor body, you can use these references and methods: this Refers to current object super Refers to superclass super.methodName() Calls a superclass's method this(...) Calls class's constructor super(...) Calls superclass's constructor return [ value ] Returns a value Importing import package.className Imports specific class name import package.* Imports all classes in package package packagename Classes in this file belong to this package interface interfaceName [ extends anotherInterface ] block [ public ] interface interfaceName block [ abstract ] interface interfaceName block Guarding synchronized ( object ) block Waits for lock on object try block Guarded statements catch ( exception ) block Executed if exception is thrown [ finally block ] Always executed try block [ catch ( exception ) block ] finally block Same as previous example (can use optional catch or finally but not both) Contact [e-mail] with questions or comments. Copyright 1998 EarthWeb Inc., All rights reserved. PLEASE READ THE ACCEPTABLE USAGE STATEMENT. Copyright 1998 Macmillan Computer Publishing. All rights reserved.