Hello World !

Simple Java Program for beginners (The HelloWorld.java)

 

Java is powerful programming language and  it is used to develop robust applications. Writing a simple Hello World program is stepwise step. This short example shows how to write first java application and compile and run it. I am assuming that latest version of JDK is installed on your machine

1. HelloWorld.java - the source code for the "Hello, world!" program

class HelloWorld {  public static void main(String[] args)  {  System.out.println("Hello World!");  } }

2. How to save 
To run this program, save it in a file with the name HelloWorld.java. It must be sure that the file name must match the name of the class.

3. Compile the program :

javac HelloWorld.java command is used to compile the source code.  When you compile the program you'll create a byte-code file named HelloWorld.class. You can confirm this with the dir command in the DOS/Windows world.

4. Execute the byte code :

Now you can execute the byte code in the Java interpreter with this command:
java HelloWorld

5. Output of the program :

When you run the program at the command line, you'll see this output
Hello, world!

6. Understanding the HelloWorld.java code :

Let's examine the HelloWorld.java file. Class is the basic building block of the java program, java codes are written in the java class. 

class HelloWorld{

//Java Codes

}

Java codes are saved in the same name as the class name.java, so we have saved the file with the name "HelloWorld.java".

There is one method  public static void main (String[] args)  which is necessary to for any class to be runnable. This function is the entry point of the execution. And the code System.out.println("Hello World!"); actually writes the Hello World! on the screen