Java Developer
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.s Java platform (Java 1.0 [J2SE]).
As of December 08 the latest release of the Java Standard Edition is 6 (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.
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 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:
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/Vista/7 operating system.
Java JDK 5/6/7
Microsoft Notepad or any other text editor
Downloading and Installing Java On Windows:
Go to http://java.sun.com and download the latest Version of Jave SDK or any Jace SDK as per your requirement and install on your system.
2. Accept all of the defaults and suggestions, but make sure that the location where Java will be installed is at the top level of your C: drive. Click on "Finish." You should have a directory (folder) named C:j2sdk1.5.0_04, with subfolders C:j2sdk1.5.0_04in and C:j2sdk1.5.0_04lib
4. Modify your system variable called "PATH" (so that programs can find where Java is located).
To do this for Windows 2000 or XP, either right-click on the My Computer icon or select "System" on the control panel. When the window titled "System Properties" appears.
5. Modify or create a system variable called "CLASSPATH," as follows. In the lower "System Variables" pane choose "New..." and type in Variable Name "CLASSPATH" and value (note that it begins with dot semicolon)
6. To test Java to see if everything is installed properly, open a command window (a DOS window) and type the command "javac" The result should be information about the Usage of javac and its options. If you get a result that "'javac' is not recognized as an internal or external command, operable program or batch file" then there is a problem and Java will not work correctly.
Java Hello World Program
Our first application will be extremely simple - the obligatory "Hello World". The following is the Hello World Application as written in Java. Type it into a text file or copy it out of your web browser, and save it as a file named HelloWorld.java. This program demonstrates the text output function of the Java programming language by displaying the message "Hello world!". Java compilers expect the filename to match the class name.
A java program is defined by a public class that takes the form:
public class program-name
{
optional variable declarations and methods
public static void main(String[] args)
{
statements
}
optional variable declarations and methods
}
Source Code:-
In your favorite editor, create a file called HelloWorld.java with the following contents:
/** Comment
* Displays "Hello World!" to the standard output.
*/
class HelloWorld
{
public static void main (String args[])
{
System.out.println("Hello World!"); //Displays the enclosed String on the Screen Console
}
}
To compile Java code, we need to use the 'javac' tool. From a command line, the command to compile this program is:-
javac HelloWorld.java
For this to work, the javac must be in your shell's path or you must explicitly specify the path to the program (such as c:j2seinjavac HelloWork.java). If the compilation is successful, javac will quietly end and return you to a command prompt. If you look in the directory, there will now be a HelloWorld.class file. This file is the compiled version of your program. Once your program is in this form, its ready to run. Check to see that a class file has been created. If not, or you receive an error message, check for typographical errors in your source code.
You're ready to run your first Java application. To run the program, you just run it with the java command:
java HelloWorld
Output
HelloWorld
