My first java program

Class Hello

{

        public static void main(String args[])

        {

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

        }

}

Setup to compile and run your first java program

Step 1. Save the file as Hello.java

Step 2.Open command prompt and go to the directory where you have saved the first java                   program as Hello.java ,assuming it is C:\

Step 3.Type javac Hello.java  and press return to compile your code.If there is no error in the             code, the command prompt will take you on next line of the window.

Step 4.Now type java Hello to run your program.

Step 5.You will able to see Hello World printed on the command prompt. 

Importance of public static void main(String args[])

whether a class contains main( )  or not and whether main( ) is declared according to the requirements ,these all things are not be checked by the compiler,these are checked by jvm at Runtime .

Note: If JVM is unable to find main( ) then we will get a Runtime Exception saying : Exception in thread "main" java.lang.NoSuchMethodError: main

public: jvm calls main() from anywhere i.e (with in class,outside the class,outside the package etc) so it is public

static: without creating object also jvm has to call this method

void: here main( ) won't return anything to JVM

main( ): this is the method which is already configured in jvm

String[] args: commandline- arguments in the form of array of instances of the class String

There are several changes can be made in prototype of main() method:

1.The order of access modifier is not important ,we can use both public static or static public

2.We can declare String array in any acceptable form

            String args[ ]

            String[ ] args

            String [ ]args

3.We can replace String args[ ] with the variable paremeter

            public static void main(String...args)   3 dots represents variable parameter

4.Instead of argument we can use any variable(valid identifier)

            public static void main(String viku[ ])

5.We can declare the main( ) method with the following modifiers also

             final

             synchronized

             strictfp

   i.e final synchronized strictfp staic void main(String args[ ])