JAVA 2 : THE COMPLETE REFERENCE

Tutorial 3 - Control Flow

2009-05-17T02:10:00.001-07:00

NOTE : - THIS IS NOT THE ORIGINAL CONTENT

Tutorial 3 - Control Flow

This tutorial on basic Java control flow assumes some introductory programming experience in another language.

Conditional Statements

Conditional statements execute a block or set of other statements only if certain conditions are met. The condition is always enclosed in round brackets. The statements to be performed if the condition is true are enclosed in curly brackets. For example:

if (value > 5) {x=7;}

Note: If the block (ie. curly brackets) contains only one statement, you may leave the brackets off. But this is not good programming practice. The curly brackets make the code more consistent and easier to read.

Occasionally you may want to perform some actions for the false outcome of a condition as well. The else keyword is used to separate branches.

if (name == "Fred") {x=4;}   else {x=20;};

Note: When the conditional if statement is used only to make an assignment to one variable, you can use the terse Cconditional operator. A simple example is:

x=(name == "Fred") ? 4 : 20;

Loops

For statements allow a set of statements to be repeated or looped through a fixed number of times. The round bracket contains initializer(s) ; conditional test ; incrementer(s). If more than one initializer or incrementer is used they are separated with commas. The test condition is checked prior to executing the block. The incrementing is doneafter executing the block. For example to output #1 #2 etc.(or #5 #4 etc.) on separate rows you could write:

for (int i=1;i<=5;i++) {document.writeln("#"+i);}; for (int i=5;i>=1;i--) {document.writeln("#"+i);};

Note: A special case of the for loop is the infinite loop for (;;){...}. This could be used with appropriate 'breakout' logic where a continuous operation was needed.

Caution: For loops can be written in ways that violate structured programming principles by allowing counter variables to be used outside of the scope of the loop block if they are defined outside the loop. Avoid the looseness of the language by always localizing the loop variable.

The enhanced for statement allows iteration over a full set of items or objects. For example:

int[] squares={0,1,4,9,16,25}; for (int square : squares) {...;} // is equivalent to for (int 1;iWhile statements allow a set of statements to be repeated or looped until a certain condition is met. The test condition is checked prior to executing the block. For example to output #1 #2 etc. on separate rows you could write:
int i=0; while (i<=5) {    document.writeln("#"+i); i++;    };
Do While statements allow a set of statements to be repeated or looped until a certain condition is met. The test condition is checked after executing the block. For example to output #1 #2 etc. on separate rows you could write:
int i=1; do {    document.writeln("#"+i); i++;    } while (i<=5);
The Switch Statement
Switch (or case) statements are used to select which statements are to be executed depending on a variable's value matching a label. default is used for the else situation. Note that the selection variable can only be int or chardatatype.
switch (selection)    {    case '1': System.out.println("You typed a 1"); break;    case '2': System.out.println("You typed a 2"); break;    default : System.out.println("Oops!, that was an invalid entry.");    };
Continue, Break and Return
Continue statements are used in looping statements to force another iteration of the loop before reaching the end of the current one. Most often continue is used as part of a conditional statement that only happens in certain cases. The following is a trivial example.
int x=0; while (x <>Break statements are used in looping and 'switch' statements to force an abrupt termination or exit from the loop or switch. In the following example the loop is never completed. Once again the normal use of break is as part of a conditional statement.
int x=0; while (x <>Return statements are used to force a quick exit from a method. They are also used to pass values back from methods.
Command Line Arguments
Command line arguments are accessible through the args[] array (assuming that args is the name used in the specification for main [Note: args[] is a Java coding convention!]). The array does not include the interpreter javacommand or the class name and the count starts at 0. Each argument is passed as a string but may be converted as in the following:
int w=Integer.parseInt(args[0]); // or sometimes you want the argument to be a character type char s=args[1].charAt(0); // uses first letter of argument only
Note: The methods parseInt() and charAt() are referenced in the type wrappers and string class topics.
Warning: Double quote marks are consumed by the command line parser and are not passed on to the args[] array!
The number of arguments passed in from the command line can be determined by using the args.length property. This is important when testing for required arguments, when there is a variable number of arguments or when there is an unpredictable number of arguments (eg. the file glob expansions (* and ?) in batch operation).
Command line options are arguments with a prefix of - (dash) and is UNIX-centric. They normally precede pathnames in the command line. Options are normally a single character but sometimes are a number or followed by a number. Examples of command line options are:
pr -d *.htm  ; print double spacing lines head -10 *.htm ; show first 10 lines head -c 10 *.htm ; show first 10 characters
Command line switches are arguments with a prefix of / (slash) and is msDOS-centric. They normally toggle boolean flags but can be found in many variations such as a following argument qualifier or a parsing situation. Depending on programmer, they may have to precede or follow file arguments.Examples are:
find /p fred *.htm  ;page pause requested progname /help ;help or man page requested format /head=4. *.htm ;include 4 lines of header space print -lines 45 *.htm ;print first 45 lines of file(s)
Note: I personally prefer switches to options but YMMV! Try to develop a standard argument option|switch handling routine that is as user tolerant as possible regarding switches and filenames. The routine should identify switches by the prefix / and act appropriately. Routines that are accessing filenames from the args[] array should skip switches (as identified with the / prefix). You may want to view the one used in include.java.
Project: Basic Problems
This project is a series of simple problems that use arrays, loops, command line arguments for input and a simpleSystem.out.println(string); statement for output.
Problem 1: Write a program that allows you to create an integer array of 18 elements with the following values:int A[]={3,2,4,5,6,4,5,7,3,2,3,4,7,1,2,0,0,0}. The program computes the sum of element 0 to 14 and stores it at element 15, computes the average and stores it at element 16 and identifies the smallest value from the array and stores it at element 17.
Problem 2: Write a program that accepts two numbers from the command line and prints them out. Then use a for loop to print the next 13 numbers in the sequence where each number is the sum of the previous two. For example:
input> java prob2 1 3 output> 1 3 4 7 11 18 29 47 76 123 322 521 843 1364
Problem 3: Write a program that accepts two numbers in the range 1 to 40 from the command line. It then compares these numbers against a single dimension array of five integer elements ranging in value from 1 to 40. The program displays the message BINGO if the two inputted values are found in the array element. For example:
input>java prob3 3 29 output>Your first number was 3        Your second number was 29        Its Bingo! // this message if 3 and 29 is found in the array        Bokya!     // this message if 3 and 29 is not found in the array        The array was 7 25 5 19 30
An extension for problem 3 would be to generate the array of five unique integers using random numbers
Problem 4: Create a program using loops to form this figure:
         n=3                n=4           *                  *          *$*                *$*         *$*$*              *$*$*          *$*              *$*$*$*           *                *$*$*                             *$*                              *
 
Project: Metric Converter
This project tests your knowledge of syntax without getting too involved in the complexities of object manipulation or a user interface. A toy metric converter should be just about right as it allows three basic stages of application development; IPO, branching, and switch selection.
The First Stage [Input - Process - Output]
The goal of the first stage of this project is to input from the command line a temperature given in degrees Fahrenheit (a geezer's unit), calculate the value in Celsius (the modern way) and then display the answer. This will test your ability to get some input, do a math process and finally display the output. It also gives some practice working with the development environment and doing compilations.
The basic input procedure will be to get the Fahrenheit reading from the command line using the methodInteger.parseInt(args[0]) which returns an integer from the first argument on the command line.
The math processing part is really easy. Celsius, a scientist, used water as his gauge so freezing was 0 and boiling was 100. Fahrenheit, an engineer used a more commonly available liquid, alcohol for his range :-). As alcohol freezes at lower temperatures, that is why the 32° difference. Because of the difference in range from freezing to boiling of the two liquids the ratio of size of the units turns out to be 100 to 180 or 5 to 9. This is the basic principle for the formuladeg_C=((deg_F-32) * 5)/9. Since division may produce a real number with a decimal value, you should cast the input number into a double and work with double precision floating point numbers (aka real numbers). Caution: Be sure to rewrite the formula with decimal numbers!
Once the answer is calculated, it can be output to your display by using the method System.out.println(deg_C)
Note: This program must be run from the command line with an integer following the program name. No error checking has been done yet!
Second Stage [Branching]
The second stage is to modify the application so that the conversion can be made in either direction. This will require a logical branch based on some additional input. Let's say the input has to look like 40 F or 10 C
    char units=args[1].charAt(0);     units=Character.toUpperCase(units);     if (units == 'F')     {     //do F --> C conversion     }     else     {     //do C --> F conversion     }
Also the command line should be checked to make sure that the number of arguments is correct (which we failed to do in stage one). A simple error message can be printed after checking the count such as:
    if (args.length != 2)     {       System.out.println ("Usage: Metric_2 ## F|C");       return;     }
Third Stage [Switches]
The third stage is to use the units argument to select an appropriate conversion routine (temperature, mass, distance, etc.) and switch to routines accordingly. For our program just add routines to convert lbs to kilograms and kg to lbs. This stage maxes out the limits of programming in the small. In later tutorials you will learn how to use custom objects to encapsulate data and procedures as well as how to use GUI objects to allow for interactive input.
switch (units) {   case 'F': { /* conversion routine */ } ; break;   case 'C': { /* conversion routine */ } ; break;   case 'L': { /* conversion routine */ } ; break;   case 'K': { /* conversion routine */ } ; break;   default : System.out.println("Oops! I do not understand the units..."); }


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Tutorial 2 - Syntax & Grammar

2009-05-16T12:38:00.000-07:00

NOTE : - THIS IS NOT THE ORIGINAL CONTENT

Tutorial 2 - Syntax & Grammar

Java like many languages (eg. C, JavaScript, awk, perl) is based on a common syntax and grammar developed by the Bell Labs in the 60's. This makes it easy to cross over from one language to another based on program requirements, resources and politics. This tutorial on basic Java syntax and grammar (ie. programming in the small) assumes some introductory programming experience in another language.

literal constants
variables and arrays

Lexical Structure

The lexical structure of a programming language is the set of elementary rules that define what are the tokens or basic atoms of the program. It is the lowest level syntax of a language and specifies what is punctuation, reserved words, identifiers, constants and operators. Some of the basic rules for Java are:

Java is case sensitive.
Whitespace, tabs, and newline characters are ignored except when part of string constants. They can be added as needed for readability.
Single line comments begin with //
Multiline comments begin with /* and end with */
Documentary comments begin with /** and end with **/
Statements terminate in semicolons! Make sure to always terminate statements with a semicolon.
Commas are used to separate words in a list
Round brackets are used for operator precedence and argument lists.
Square brackets are used for arrays and square bracket notation.
Curly or brace brackets are used for blocks.
Keywords are reserved words that have special meanings within the language syntax.
Identifiers are names for constants, variables, functions, properties, methods and objects. The first charactermust be a letter, underscore or dollar sign. Following characters can also include digits. Letters are A to Z, a to z, and Unicode characters above hex 00C0. Java styling uses initial capital letter on object identifiers, uppercase for constant ids and lowercase for property, method and variable ids.
Note: an identifier must NOT be any word on the Java Reserved Word List.

Data Types

Java is a strongly-typed language. Its primitive data types are:

Type	Bits	Range
boolean	1	true, false
char	16	0 to 65,535
byte	8	-128 to +127
short	16	-32,768 to +32,767
int	32	-2³² to +2³²-1
long	64	-2⁶⁴ to +2⁶⁴-1
float	32	-3.4E+38 to +3.4E+38 (approx)
double	64	-1.8E+308 to +1.8E+308 (approx)

Literal Constants

Literal constants are values that do not change within a program. Numeric constants default to integer or double unless a suffix is appended. Note that a character can be represented by an ASCII equivalent. The literal types are:

Boolean: true, false
Character: 'c', '\f'
String: "Fred", "B and E"
Null: null

Integer: 5, 0xFF (hexadecimal)
073 [leading zero] (octal), 5l (long), 0xFFlD (hex)
Floating Point: 2.543, -4.1E-6 (double)
2.543f, 8e12f (float)

Note: Do not use leading zeros to format integers as this can cause an unintended octal meaning. Use spaces instead!

Escape (aka backslash) characters are used inside literal strings to allow print formatting as well as preventing certain characters from causing interpretation errors. Each escape character starts with a backslash. The available character sequences are:

Seq	Name	Seq	Name
\b	backspace	\f	formfeed
\t	horizontal tab	\"	double quote
\n	newline	\'	single quote
\r	carriage return	\\	backslash
\###	Latin encoded character	\uHHHH	Unicode encoded character

Variables

Variables are temporary data holders. Variable names are identifiers. Variables are declared with a datatype. Java is a strongly typed language as the variable can only take a value that matches its declared type. This enforces good programming practice and reduces errors considerably. When variables are declared they may or may not be assigned or take on a value (initialized). Examples of each of the primitive datatypes available in Java are as follows:

byte x,y,z;             /* 08bits long, not assigned, multiple declaration */ short numberOfChildren; /* 16bits long */ int counter;            /* 32bits long */ long WorldPopulation;   /* 64bits long */  float pi;               /* 32bit single precision */ double avagadroNumber;  /* 64bit double precision */ boolean signal_flag;    /* true or false only */ char c;                 /* 16bit single Unicode character */

Variables can be made constant or read only by prepending the modifier final to the declaration. Java convention uses all uppercase for final variable names.

Arrays

Arrays allow you to store several related values in the same variable (eg. a set of marks). Declaration of an array only forms a prototype or specification for the array. Multi-dimensional arrays are considered to be arrays of arrays (of arrays...). Note that in a declaration the brackets are left blank.

int i[];        /* one dimension array */ char c[][];     /* two dimension array */ float [] f;     /* geek speak way */ Bowl shelfA[];  /* array of objects */

Array memory allocation is assigned explicitly with the new operator and requires known static bounds (ie. number of elements). The number of items in an array can then be determined by accessing its length property. For a two dimensional array named m, m.length gives the number of elements in its first dimension and m[0].length gives the number of elements in its second dimension.

Array1 = new int[5]; //previously declared, now created int markArray[] = new int[9]; //declaration and allocation at same time int grades[] = new int[maxMarks]; //maxMarks must be a positive integer

Array initialization can take place at declaration. Size of the array is determined by the contents.

String flintstones[] = {"Fred", "Wilma", "Pebbles"}; //init values String pairs[][] = {  {"Adam","Eve"},{"Lucy","Ricky"},{"Fred","Ethel"},{"Bert","Ernie"}};

Operators and Expressions

Operators are actions that manipulate, combine or compare variables. They fall into several categories as follows:

Assignment:           = += -= *= \= %= Arithmetic:           + - * / % (modulus) ++ (increment) -- (decrement) String Concatenation: + Comparison:           == != > >= < <= Boolean Comparison:   ! & | ^ && || (&& are short circuit ops) Bitwise Comparison:   ~ & | ^ (xor) << >> >>> Bitwise Assignment:   &= |= ^= (xor) <<= >>= >>>= Conditional:          ? (eg (expr1) ? expr2 : expr3 ) Object Creation:      new (eg int a[] = new int[10];) Class of Object:      instanceof Casting of Type:      (var_type)

Note: Changes in data type are done explicitly using a cast operation. For example a = (int) b; assumes a is of type int and b is of another type.

Expressions are phrases used to combine values and/or operands using operators to create a new value. One example of an expression is 5 + 3.

Conditions, Statements and Blocks

Conditions are phrases that can be evaluated to a boolean value such as a comparison operator between two constants, variables or expressions used to test a dynamic situation. Examples are x <= 5 and bool_flag != true.

Statements are complete program instructions made from constants, variables, expressions and conditions. Statements always end with a semicolon. A program contains one or more statements.

Assignment statements use an assignment operator to store a value or the result of an expression in a variable. Memory allocation is done at the time of assignment. Primitive datatypes have static allocation with size determined by their type. Simple examples include first_name = "Fred"; and count +=;

Variables may be assigned an initial value when declared. This is considered good programming practice. Examples are boolean fileOpenFlag = true;, int finalScore = null; and final float PI = 3.14159;

Array variables can use a shortcut method of initial value assignment. Examples are:

int v[] = {2,4,20}; //declaration/creation/assignment in one step! int m[][] = {{2,3,4}, {4,5,6}, {1,1,1}}; // two dimensional array

Local variables must be assigned a value prior to use. There is no default assumption. Failure to initialize will cause a compiler error! Field variables (aka properties) have defaults but initialization is good programming practice.

Execution blocks are sets or lists of statements enclosed in curly brackets. Variables maintain their definition (or 'scope') until the end of the execution block that they are defined in. This is the reason why variable declarationand assignment can be a two step process.

Note: It is a good rule of thumb to declare variables in as nested a scope as possible to limit the chance of spurious assignment.

Beware: A variable's content can be hidden by redeclaration of its name within a nested execution block. At times this is convenient but beginning programmers should avoid reuse (ie. 'overload') of variable names.

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Tutorial 1 - Objects, Applications & Applets

2009-05-16T12:29:00.000-07:00

NOTE : - THIS IS NOT THE ORIGINAL CONTENT

Tutorial 1 - Objects, Applications & Applets

The first Java tutorial covers the topic of objects/classes as well as outlining the basic structure of Java applications and applets.

What Are Objects

Java is an object-oriented programming language. But what are objects? An object is a self-contained entity which has its own private collection of properties (ie. data) and methods (ie. operations) that encapsulate functionality into a reusable and dynamically loaded structure. After a class definition has been created as a prototype, it can be used as a template for creating new classes that add functionality. Objects are programing units of a particular class. Dynamic loading implies that applications can request new objects of a particular class to be supplied on an 'as needed' basis. Objects provide the extremely useful benefit of reusable code that minimizes development time.

The Basic Structure of an Application

A Java application resembles a program in most compiled languages. Compiled bytecode resides on the user's machine and is executed by a run-time interpreter that has to be user installed.

Previously you wrote a simple 'hello world!' application to test the development environment. Now comes the explanation of the basic structure of a Java application using it as an example. Applications are stand alone programs and are executed by using a Java interpreter.

/* The HelloWorldApp class implements an application * that displays "Hello World!" to the standard output. */ public class HelloWorldApp { public static void main(String args[]) { // Display Hello World! now System.out.println("Hello World!"); } }

The first two lines is a comment statement about the application's function. Comments are not required but are extremely useful as documentation within the source. Other notes and doc files may get lost but these stay right where they are most useful. A long comment starts with a /* or /** and ends with a */ Short one line comments begin with // and end with the .

The third line starts with the reserved word public. This indicates that objects outside the object can invoke (ie call or use) it. The reserved word class indicates that we are building a new object specification (aka template) with the name that follows. HelloWorldApp is the class name (your choice) and is case sensitive. Java 'style' capitalizes only the first letter of each class name. Line four is an opening curly bracket that marks the start of the class definition.

Line five is the specification of a method (aka procedure in older languages). static indicates that it calls a class method and not an 'instance' method. The method's name is main and the reserved word void indicates that no result is returned. main has parameters in round brackets. String args[] indicates that any command line argument values given are being passed to main as an array of String type in the variable args. Line six has an opening bracket for the main() method.

Line eight invokes the println() method of the system.out object. The data to be printed is passed in the argument as a string datatype. Note that each Java statement concludes with a semicolon. Finally, closing curly brackets are used for the main and for the object definition.

The Basic Structure of an Applet

A Java applet produces object code which can be interpreted within the user's browser. This means that naive users do not have to fuss with program installation. Applets also provide security by restricting local user resource access. Applets can be useful, user friendly programs as demoed by ChemJava or a lot of fun as seen on Jigzone.

Here is the explanation of the basic structure of a Java applet using the one that you wrote to test your working environment. Applets are placed in XHTML documents and are executed from within a Java aware browser.

/* The HelloWorld class implements an applet that displays "Hello World!" within an XHTML document. */ import java.awt.*; import java.applet.*; public class HelloWorld extends Applet { public void init() // Initialize the canvas { Color lightgray=new Color(211,211,211); // customize setBackground(lightgray); // make mellow background resize(150,10); } public void paint(Graphics g) // Display Hello World! { g.drawString("Hello World!",50,25); } }

Line three uses the reserved word import which indicates that objects from external libraries awt and applet are going to be used. Line four uses the reserved word extends to indicate that the class being created is a subclass of the Applet class. This demonstrates how Java code is reused and extended.
Note: The JApplet class is used instead of Applet whenever Swing GUI is used.

Line six starts the override (change) of the java.applet.Applet class init() method. Line eleven invokes the resize()method of the Applet object and sets the window dimensions. Note the all important statement ending semicolon.

Line 12 is another method override declaration. This time it is the paint() method of the Applet object. It is being passed an object of the Graphics class called g. Line 14 tells the Graphics object g to invoke its method drawString()using the string "Hello World! and position it at point (50,25) in the previously assigned window. A later tutorial gives details on graphics programming within applets.

Viewing Applets in XHTML Docs

Applet elements are placed inside the body element of an XHTML document. An applet skeleton is as follows:

Browser does not support Java applets!

code points to the previously compiled applet class that is contained in a separate file. codebase points to the folder that the class file is in. A good choice is place the class folder under the html document. Be sure to explicitly point at the codebase starting at the html document. If you need to start at a local root, use file:///C:/. Anything else fails in FireFox! height and width are also required parameters and cannot be moved into style rules. Nested paramelement(s) are optional and can be used to feed data to the applet from the XHTML document. An example would be The applet would use varColor=getParam("var_color"); to access the value. Always include a message for non-java browsers between the applet element tags. The resulting display is:

Note 1: Remember that filenames are case sensitive in Java. Some browsers may allow helloworld.class but Opera obeys the rule! Always test any applet on as many browsers as you can.

Note 2: Although styling attributes such as align, hspace and vspace are mentioned in many texts, they are archaic and should be replaced by CSS style rules. And of course all XHTML documents should have a doctype and validate to current w3.org recommendations.

Note 3: The applet element has been deprecated and may only be used in Transitional documents. To use a Strictdoctype you must convert applet elements to object elements.The equivalent object element syntax is more complex as FireFox/Opera have native support for Java while MSIE/Safari use plugins. Refer to object elements for a demonstration and source code.

Life Cycle of an Applet

Each Java applet goes through a sequence of stages. They are created (initialized), displayed (painted), paused while off screen (stopped, started) and finally removed (destroyed) when over.

Initialization occurs when the applet is first loaded. Tasks performed here are creating objects, setting initial state, loading images, fonts, etc. and setting parameters. The method used is init()

Display is how things are drawn on screen whether it is text, graphics or background. Redisplay occurs many time through the life of an applet. The method used is paint(Graphics g).

Stopping occurs when one leaves a page that contains a running applet. Threads normally continue running but can be manually stopped. The method used is stop().

Starting occurs after initialization and after stops occur. Tasks include starting threads, sending messages to helper objects, or to tell the applet to start running. The method used is start().

Destruction cleans up an applet before the browser exits. Tasks include thread stopping. Normally the methoddestroy() is not overridden.

Cautions About Applet Use

The greatest problem with using applets is there is no defined standard implementation method. Some browsers support Java natively (ie. self contained) but this leads to version compatibility issues. Other browsers use a Java plug-in module. But this sometimes requires that the viewer download and install Java. And there are some primitive browsers that offer no Java support at all. Most browsers also open a box that will overwrite any text that the box is scrolled to (ie a high z-index value). At this point JavaScript looks like a more consistent method of utility delivery!

For security purposes, Java applets normally allow NO access to user resources! Local files can not be accessed. Only the current website server can be communicated with. Printers can't be used. If your project can live with those restrictions then an applet may be more appropriate than an application.

Note: Digitally signed applets revealing the author can be accepted by a user and run with full application privileges.

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JAVA INTRODUCTION : Java Authoring Info

2009-05-16T12:16:00.000-07:00

NOTE : - THIS IS NOT THE ORIGINAL CONTENT

Java Authoring Info

ava is a modern, platform independent programming language that is object-oriented for reusability of code modules. This page explains why one would use Java (with a few cautions), how one can install the Development Kit (JDK), and provides simple test applications and applets to make sure everything you need is ready. Links are provided to tutorials and code samples for those who prefer to roll their own utilities or adapt other's projects. I have also included my own Java tutorials complete with suggested projects that reinforce the material presented.

Why Use Java

Why should one use Java as an authoring language?

Modern concepts such as object oriented programming can be rolled over into other languages
Java is easy to learn as no user programmed memory management or pointers are involved
Java is open source and may be modified by any user to his requirements.
Java applications and applets are platform independent
Java is robust, learning from mistakes of older languages
Java is security conscious and enforces it through a virtual machine paradigm
Java is complete, and many complex projects such as JEdit [a syntax aware editor]
and Alice [a 3D programming language] have been developed in Java.

Cautionary Notes

Do not believe documentation. Test for yourself. Even sun.com makes errors as it does in the System.in.read() method. Keystrokes are read as integers, not characters.

Be prepared to test Java applets with at least two versions of each of the major browsers. Remember that there are also browsers that have no Java support whatsoever and that some users turn Java OFF by choice. This is not a Java problem but one of browser conformance to the w3.org recommendations. The situation is improving however!

Installing the Java Developer's Kit

Sun MicroSystems designed and developed Java and control the 'essence' of the language. The current version of the Java Development Kit is JDK 6-Update 13. Those with older operating systems may need to consult the archives. If you want to use the Java visual development environment (IDE), select with NetBeans instead of the basic JDK. NetBeans also allows visual layout of GUI interfaces once you have learned how to use the Swing class. Other IDEs that you may be interested in are: MicroSoft Visual Studio, DrJava, Eclipse, JBuilder and JCreator.

Note: Although some programmers find using an Interactive Development Environment (IDE) helpful in larger projects, many find learning the IDE confuses them with learning Java itself. A basic text editor is sufficient for Java. Use the method that you are comfortable with.

Run the installer program. WARNING: Do not try to change the directory that the JDK loads into. Not all software providers are careful to make the root independent ;-[ ;-[. I came to much grief on that assumption.

Wintel User Note: The system environment variable path will have to be set within AUTOEXEC to point at the Java binary file installation directories.

MSDOS:	EDIT Autoexec.bat
Windows 9x:	Start -- Run -- Sysedit
Windows XP:	Start - Settings - Control Panel - System - Advanced - Environment Variables

You may want to create a classroom or playground folder for your project java class files that need access from anywhere. Add this folder name to the classpath system environment variable. Note: Make sure the classpath string starts with .; so that the current directory is searched before other directories are.

Wintel User Note: NotePad will do as an editor but several features of more advanced editors are helpful. A very strongly recommended choice is TextPad which is Java aware (reserved words and punctuation are color coded) and can handle multiple files for easy cut-and-paste. If you install TextPad, be sure to place the Java quick compilation items in the tools menu by using Configure - Preferences - Tools - Add - Sdk.

Test Samples

java.com will run a check to verify that the Java Runtime Environment (JRE) has been installed correctly.

Use the following simple HelloWorld application and applet to test that the SDK development environment has been installed correctly. For a complete explanation of the code's syntax, refer to the first tutorial on Objects, Applications and Applets.

Your First Java Application

/* The HelloWorldApp class implements an application that * displays "Hello World!" to the standard output device. */ public class HelloWorldApp { public static void main(String args[]) { // Display "Hello World!" System.out.println("Hello World!"); } }

Cut and paste the above source code or type it into your favorite editor. Save the file as HelloWorldApp.java in your Java working folder (say JavaStuff, JavaTutor, sandbox, etc.).

Next compile the source file into bytecode by using the command javac HelloWorldApp.java. If an error message stating Not Found occurs, type the command javac. If there is still an error message it means that the path needs setting (see the above note on installing). If there is no error at this point then the .java file is missing or there was a typing error. Most typing errors are due to case sensitivity. In Java, UPPER and lower case ARE different.

Finally run the application with the Java interpreter by using the command Java HelloWorldApp. For a complete explanation of the code's syntax, please refer to Basic Structure of a Java Application.

Your First Java Applet

/* The HelloWorld class implements an applet that * displays "Hello World!" within an html document.*/ import java.awt.*; import java.applet.*; public class HelloWorld extends Applet { public void init() // Initialize canvas { Color lightgray=new Color(211,211,211); // customize setBackground(lightgray); // make mellow background resize(250,50); } public void paint(Graphics g) // Display "Hello World!" { g.drawString("Hello World!",60,25); } }

Cut and paste the above source code or type it into your favorite editor. Save the file as HelloWorld.java in your Java working folder (say JavaStuff, JavaTutor, sandbox, etc.).

Next compile the source into bytecode by using the command javac HelloWorld.java. If an error message statingNot Found occurs, type the command javac. If there is still an error message it means that the path needs setting (see the above note on installing). If there is no error at this point then the .java file is missing or there was a typing error. Most typing errors are due to case sensitivity. In Java, UPPER and lower case ARE different.

Next create an html document that includes the following in its body.

Now view the html document in your favorite browser. For a complete explanation of the applet's syntax, please refer to Basic Structure of a Java Applet.

JR's Java Tutorials

Do you want to learn more about Java programming! Do you have an applet or application that you want to write for yourself. Then get your favorite editor ready and jump into my set of tutorials on the fundamentals of Java. They include plenty of samples and projects. And if you have questions or want to provide feedback, please email me.

Note: For those who prefer to work off-line, I have created a fileGrab utility in Java that will download all Java tutorials, source code zip packages, and required supplementary files. Follow these steps to get the tutorial material:

Create a new folder that will contain the fileGrab utility and the tutorial material.
Move into the folder and download the network utilities zip file [12 kb]
Unzip the files named fileGrab.java and fileGrab.bat
Compile the application using the command javac fileGrab.java.
Download javapack.lst, the current list of tutorial files to be downloaded for off-line viewing.
Run the application using the command fileGrab.bat.
Use your browser to test that all the files are ready to use offline. The root file is jaintro.htm (this page)

Tutorials and Code Samples

The following sites provide tutorial material for Java. Combined with good textbooks, all the required topics should be well covered. Sun also provides a Coding Conventions document to help standardize your work.

Swing Tutorials - S Davidson, Heriot Watt
Java 5.0 - B Kjell, Central Connecticut State
JavaCoffeeBreak Tutorials
Lindsey's Course with Tech&Physics Apps

Java technologies can be used to create applications and applets with rich client interfaces that are secure, portable high-performance and run on multiple operating systems. The JavaDesktop community of java.net provides the latest news and information for developers of client applications for the J2SE platform. Don't miss the news, features, forums and projects at java.sun.com

Why should you create code to do something if someone else has already written it? There are many finished Java programs and utilities that are ready-to-run. The following sites may already have the functions you want and probably many more that you didn't even think about. Spend some quality time trolling for ideas!

ChemJava - links to science and math stuff!
Java Almanac - links to examples from text

Sun's Code Samples
Sun.com - lots of applets to draw ideas from

Most of these projects are packaged in JAR (Java Archived Resource) files which are similar to zipped packages in Windows. To unpackage a .jar file you use the commands:

java -jar file_name.jar
jar -x file_name.jar. If you just want to view the contents first, use the -tf option instead of -x.

BIBLIOGRAPHY / REFERENCE : -

FOR REFERENCE....PLEASE VISIT :

http://home.cogeco.ca/~ve3ll/jaintro.htm

P.S. : THIS CONTENT IS TAKEN FROM THE ABOVE MENTIONED SITE

Learn About Java Technology

2009-05-16T12:05:00.000-07:00

NOTE : - THIS IS NOT THE ORIGINAL CONTENT

Learn About Java Technology

To date, the Java platform has attracted more than 6.5 million software developers. It's used in every major industry segment and has a presence in a wide range of devices, computers, and networks.

Java technology's versatility, efficiency, platform portability, and security make it the ideal technology for network computing. From laptops to datacenters, game consoles to scientific supercomputers, cell phones to the Internet, Java is everywhere!

Java powers more than 4.5 billion devices including:

800+ million PCs
2.1 billion mobile phones and other handheld devices (source: Ovum)
3.5 billion smart cards
Set-top boxes, printers, Web cams, games, car navigation systems, lottery terminals, medical devices, parking payment stations, and more.

To see places of Java in Action in your daily life, explore java.com.

Why Software Developers Choose Java

Java has been tested, refined, extended, and proven by a dedicated community. And numbering more than 6.5 million developers, it's the largest and most active on the planet. With its versatilty, efficiency, and portability, Java has become invaluable to developers by enabling them to:

Write software on one platform and run it on virtually any other platform
Create programs to run within a Web browser and Web services
Develop server-side applications for online forums, stores, polls, HTML forms processing, and more
Combine applications or services using the Java language to create highly customized applications or services
Write powerful and efficient applications for mobile phones, remote processors, low-cost consumer products, and practically any other device with a digital heartbeat

Some Ways Software Developers Learn Java

Today, many colleges and universities offer courses in programming for the Java platform. In addition, developers can also enhance their Java programming skills by reading Sun's java.sun.com Web site, subscribing to Java technology-focused newsletters, using the Java Tutorial and the New to Java Programming Center, and signing up for Web, virtual, or instructor-led courses.

What Is JavaFX

JavaFX extends your web experience by delivering rich media and content across all the screens of your life. As users, you will be able to run JavaFX applications in a browser or drag and drop them onto the desktop. It's a seamless interface!

JavaFX is powered by Java: JavaFX extends the power of Java by allowing developers to use any Java library within JavaFX applications. This way developers can expand their capabilities in Java and make use of the revolutionary presentation technology that JavaFX provides to build engaging visual experiences.

Highlights of JavaFX:

Allows users to view JavaFX applications in a browser or break free of the browser by dragging and dropping the same application onto the desktop
Enables an efficient designer-to-developer workflow with Project Nile: designers can work in their tools of choice while collaborating with Web scripters who use the NetBeans IDE with JavaFX
Extends Java technology by enabling use of any Java library within a JavaFX application
Allows developers to integrate vector graphics, animation, audio, and video Web assets into a rich, interactive, immersive application

To learn more about JavaFX technology, visit javafx.com or java.sun.com/javafx web sites for more information.

P.S. : THIS CONTENT IS TAKEN FROM THE ABOVE MENTIONED SITE

What is Java?

2009-05-16T11:31:00.000-07:00

NOTE : - THIS IS NOT THE ORIGINAL CONTENT

Java allows you to play online games, chat with people around the world, calculate your mortgage interest, and view images in 3D, just to name a few. It's also integral to the intranet applications and other e-business solutions that are the foundation of corporate computing.

> Find Out More About Java
> Download Java

After you've downloaded Java, visit java.com to check out Java in Action in your daily life.

Java software for your computer, or the Java Runtime Environment, is also referred to as the Java Runtime, Runtime Environment, Runtime, JRE, Java Virtual Machine, Virtual Machine, Java VM, JVM, VM, or Java download.

BIBLIOGRAPHY / REFERENCE : -

FOR REFERENCE....PLEASE VISIT :

http://java.com/en/download/whatis_java.jsp

P.S. : THIS CONTENT IS TAKEN FROM THE ABOVE MENTIONED SITE

HOW TO BECOME A PERFECT , PROFESSIONAL AND SUCCESSFUL PROGRAMMER

2009-05-16T07:55:00.001-07:00

Hello Learners, I am a Professional Programmer in JAVA.

I am here to give you people some tips and advices which would help you a lot in learning this JAVA Programming Language.

They are As Follows : -

1. Learn JAVA Thoroughly.

2. Get Use to all The CODES available in JAVA.

3. Get acquainted with the theory of JAVA.

4. Learning and Cramming is not all required to make you a perfect and professional programmer.

For that you need to do a lots of practice.

You got to create a lots of programs of your own and not just by copy-paste or cut-paste.

So,for becoming a successful, perfect and professional programmer,you need to do a lots of hard-work.

Hope you get it and implement all the tips which i have mentioned above.

ENJOY LEARNING !!!!!!

ENJOY PROGRAMMING !!!!!

CREATE YOUR OWN GOOD,SUCCESSFUL AND WEALTHY FUTURE BY LEARNING HOW TO CREATE PROGRAMS !!!!!! TAKE CARE !!!!!!

TAKE CARE !!!!

BIBLIOGRAPHY / REFERENCE : I HAVE TAKEN THIS ADVICE FROM MY ANOTHER BLOG WHICH IS ALL ABOUT LEARNING THEORY OF C++ AND PROGRAMMING IN C++.

PLEASE VISIT : - LEARN C++ PROGRAMMING