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The java application we are going to create is called a Hello World app and this app will simply display the greeting "Hello World!".

Practically almost all tutorials on java and beginner programmers have you to create this simple app as your first application, so you don't have to know something about java programming to be able to create this app.



In order to create this application, you'll need: The Java SE Development Kit 7 (JDK 7) and a text editor. In this case, we'll use Notepad, a simple editor included with the Windows platforms. These two items are all you'll need to write your first application.

Create a Source File

 First, start your editor. You can launch the Notepad editor from the Start menu by selecting Programs > Accessories > Notepad. In a new document, type in the following code:

/**
 * The HelloWorldApp class implements an application that
 * simply prints "Hello World!" to standard output.
 */
class HelloWorldApp {
    public static void main(String[] args) {
        System.out.println("Hello World!"); // Display the string.
    }
}

JAVA SYNTAX - Note: Type all code, commands, and file names exactly as shown. Both the compiler (javac) and launcher (java) are case-sensitive, so you must capitalize consistently.

HelloWorldApp is not the same as helloworldapp.

Save the code in a file with the name HelloWorldApp.java. To do this in Notepad, first choose the File > Save As menu item. Then, in the Save As dialog box: 

1. Using the Save in combo box, specify the folder (directory) where you'll save your file. In this example, the directory is java on the C drive.
2. In the File name text field, type "HelloWorldApp.java", including the quotation marks.
3. From the Save as type combo box, choose Text Documents (*.txt).
4. In the Encoding combo box, leave the encoding as ANSI.

When you're finished, the dialog box should look like this.

Compile the Source File into a .class File

Open a shell, or "command," window. You can do this from the Start menu by choosing Command Prompt (Windows XP), or by clicking the Start menu ... and then entering cmd. The shell window should look similar to the following figure.

If you enter dir at the prompt, you should see your source file, as the following figure shows.

 Now you are ready to compile. At the prompt, type the following command and press Enter.

            javac HelloWorldApp.java

The compiler has generated a bytecode file, HelloWorldApp.class. At the prompt, type dir to see the new file that was generated, as shown in the following figure.

Now that you have a .class file, you can run your program.

Run the Program

In the same directory, enter the following command at the prompt:

The next figure shows what you should now see: