Variable

In Java, all variables must be declared before they can be used. The basic form of a variable declaration is shown here:

Syntax:

                datatype identifier = value(if initialized)

same as,

             int a = 2;

The identifier is the name of the variable. To declare more than one variable of the specified type, use a comma-separated list.

Here are several examples of variable declarations of various types. Note that some include an initialization.

int a, b,c;                         // declare three int a, b and c.

int d=2, e=4, f=6;            // declare three more variables.

                                     // and initializing d and f.

byte z=22;                     // declare and initializes z.

double pi = 3.14159;       // double and float are used to store decimal values.

char x = 'x';                   // declare char and the value stored in

                                   // it will b a character.

String name = "Admin"   // String is not a datatype, it is a class but it is

                                  // used as a datatype.

First Program of JAVA

class test {
public static void main(String args[]) {
System.out.println("My first Program of JAVA");
}
}

- As I told u earlier that in Java we make class files and then compile it...
- static is used for using class without object.
- main() is the method which is used to execute program code and display a resultant... As I have given here a simply output "My first Program of JAVA".
- String args[] = declaring variable of named args of array type...

your comments are welcomed... :)

Introduction

Java programming language was originally developed by Sun Microsystems, which was initiated byJames Gosling and released in 1995 as core component of Sun Microsystems's Java platform (Java 1.0 [J2SE]).

The latest release of the Java Standard Edition is 7 (J2SE).

With the advancement of Java and its wide spread popularity, multiple configurations were built to suite various types of platforms. Ex: J2EE for Enterprise Applications, J2ME for Mobile Applications.

Oracle buys Sun...[Source : http://www.oracle.com/us/corporate/press/018363] 

Java is:

• Object Oriented : In java everything is an Object. Java can be easily extended since it is based on the Object model.
• Platform Independent: Unlike many other programming languages including C and C++ when Java is compiled, it is not compiled into platform specific machine, rather into platform independent bytecode. This bytecode is distributed over the web and interpreted by virtual Machine (JVM) on whichever platform it is being run.
• Simple : Java is designed to be easy to learn. If you understand the basic concept of OOP java would be easy to master.
• Secure : With Java's secure feature it enables to develop virus-free, tamper-free systems. Authentication techniques are based on public-key encryption.
• Architectural- neutral : Java compiler generates an architecture-neutral object file format which makes the compiled code to be executable on many processors, with the presence Java runtime system.
• Portable : being architectural neutral and having no implementation dependent aspects of the specification makes Java portable. Compiler and Java is written in ANSI C with a clean portability boundary which is a POSIX subset.
• Robust :Java makes an effort to eliminate error prone situations by emphasizing mainly on compile time error checking and runtime checking.
• Multi-threaded : With Java's multi-threaded feature it is possible to write programs that can do many tasks simultaneously. This design feature allows developers to construct smoothly running interactive applications.
• Interpreted : Java byte code is translated on the fly to native machine instructions and is not stored anywhere. The development process is more rapid and analytical since the linking is an incremental and light weight process.
• High Performance: With the use of Just-In-Time compilers Java enables high performance.
• Distributed : Java is designed for the distributed environment of the internet.
• Dynamic : Java is considered to be more dynamic than C or C++ since it is designed to adapt to an evolving environment. Java programs can carry extensive amount of run-time information that can be used to verify and resolve accesses to objects on run-time.

History of Java:

James Gosling initiated the Java language project in June 1991 for use in one of his many set-top box projects. The language, initially called Oak after an oak tree that stood outside Gosling's office, also went by the name Green and ended up later renamed as Java, from a list of random words.

Sun released the first public implementation as Java 1.0 in 1995. It promised Write Once, Run Anywhere (WORA), providing no-cost run-times on popular platforms.

On 13 November 2006, Sun released much of Java as free and open source software under the terms of the GNU General Public License (GPL).

On 8 May 2007 Sun finished the process, making all of Java's core code free and open-source, aside from a small portion of code to which Sun did not hold the copyright.

Tools you will need:

For performing the examples discussed in this tutorial, you will need a Pentium 200-MHz computer with a minimum of 64 MB of RAM (128 MB of RAM recommended).

You also will need the following softwares:

• Linux or Windows 95/98/2000/XP/Vista/7 operating system.
• Java JDK 7
• Microsoft Notepad or any other text editor

This tutorial will provide the necessary skills to create GUI, networking, and Web applications using Java.