First Java Program

/* First Java Program */

1.       Print Hello World using Java Program.

class HelloWorld

{

                Public static void main( String args[] )

                {

                                System.out.println( " Hello World..!!! ");

                }

}

-          Save the file with HelloWorld.java in any folder. ( You can use any name for the file, but need to execute with class name only ).

-          Open cmd. ( Goto Run, type cmd)

-          Compile & Execute the application as follows:

Javac is used to compile the application.

Java is used to execute the application.

Program Explanation:

       In Java, Entry point is main().

       Hence JVM first calls main(). To understand the java architecture, refers to above article.

       We define the class HelloWorld inorder to encapsulate main method.

       Here, class = Keyword and HelloWorld = identifier.

       Every class name should be Uppercased, if it is concate nated, each word must start with uppercase.

Ex1: Hello

Ex2: HelloWorld

                Description about main():

       Public:

Main is defined as public because to give permission to JVM to call it.

       Static:

Main is defined as static because the JVM can call it without object creation.

       Void:

It is declared as void because, JVM doesn't need any response back from main().

       String args[]:

Main contains args[] as parameter because it provides the facility to input variables from command prompt.

                Compiling and Execution: