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Java Tutorial

JAVA TUTORIAL

Simply Easy Learning by tutorialspoint.com tutorialspoint.com

TUTORIALS POINT

TUTORIALS POINT

Java Overview

Java^ programming language was originally developed by Sun Microsystems which was initiated by James

Gosling and released in 1995 as core component of Sun Microsystems’ Java platform (Java 1.0 [J2SE]). As of December 2008 , the latest release of the Java Standard Edition is 6 (J2SE). With the advancement of Java and its widespread popularity, multiple configurations were built to suite various types of platforms. Ex: J2EE for Enterprise Applications, J2ME for Mobile Applications. Sun Microsystems has renamed the new J2 versions as Java SE, Java EE and Java ME, respectively. Java is guaranteed to be Write Once, Run Anywhere. 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 byte code. This byte code 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 of Java runtime system.
• Portable : Being architectural-neutral and having no implementation dependent aspects of the specification makes Java portable. Compiler inJava 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.

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• Multithreaded : With Java's multithreaded 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 lightweight 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 being 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 7.1 or Windows 95/98/2000/XP operating system.
• Java JDK 5
• Microsoft Notepad or any other text editor This tutorial will provide the necessary skills to create GUI, networking, and Web applications using Java.

What is Next?

Next chapter will guide you to where you can obtain Java and its documentation. Finally, it instructs you on how to install Java and prepare an environment to develop Java applications.

TUTORIALS POINT

Popular Java Editors:

To write your Java programs, you will need a text editor. There are even more sophisticated IDEs available in the market. But for now, you can consider one of the following:

• Notepad: On Windows machine, you can use any simple text editor like Notepad (Recommended for this tutorial), TextPad.
• Netbeans: Is a Java IDE that is open-source and free which can be downloaded fromhttp://www.netbeans.org/index.html.
• Eclipse: Is also a Java IDE developed by the eclipse open-source community and can be downloaded from http://www.eclipse.org/.

What is Next?

Next chapter will teach you how to write and run your first Java program and some of the important basic syntaxes in Java needed for developing applications.

TUTORIALS POINT

Java Basic Syntax

When we consider a Java program,^ it can be defined as a collection of objects that communicate via

invoking each other's methods. Let us now briefly look into what do class, object, methods and instance variables mean.

• Object - Objects have states and behaviors. Example: A dog has states-color, name, breed as well as behaviors - wagging, barking, eating. An object is an instance of a class.
• Class - A class can be defined as a template/blue print that describes the behaviors/states that object of its type support.
• Methods - A method is basically a behavior. A class can contain many methods. It is in methods where the logics are written, data is manipulated and all the actions are executed.
• Instance Variables - Each object has its unique set of instance variables. An object's state is created by the values assigned to these instance variables.

First Java Program:

Let us look at a simple code that would print the words Hello World. public class MyFirstJavaProgram{ /* This is my first java program.

• This will print 'Hello World' as the output */ public static void main(String[]args){ System.out.println("Hello World");// prints Hello World } } Let's look at how to save the file, compile and run the program. Please follow the steps given below:

• Open notepad and add the code as above.
• Save the file as: MyFirstJavaProgram.java.
• Open a command prompt window and go o the directory where you saved the class. Assume it's C:.
• Type ' javac MyFirstJavaProgram.java ' and press enter to compile your code. If there are no errors in your code, the command prompt will take you to the next line(Assumption : The path variable is set).

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