The Java Tutorials have been written for JDK 8. Examples and practices described in this page don't take advantage of improvements introduced in later releases and might use technology no longer available.
See Java Language Changes for a summary of updated language features in Java SE 9 and subsequent releases.
See JDK Release Notes for information about new features, enhancements, and removed or deprecated options for all JDK releases.
It's time to write your first application! The following instructions are for users of Windows Vista, Windows 7, and Windows 8. Instructions for other platforms are in "Hello World!" for Solaris OS, Linux, and Mac OS X and "Hello World!" for the NetBeans IDE.
If you encounter problems with the instructions on this page, consult the Common Problems (and Their Solutions).
To write your first program, you'll need:
The Java SE Development Kit 8 (JDK 8)
You can download the Windows version now. (Make sure you download the JDK, not the JRE.) Consult the installation instructions.
A text editor
In this example, we'll use Notepad, a simple editor included with the Windows platforms. You can easily adapt these instructions if you use a different text editor.
These two items are all you'll need to write your first application.
Your first application, HelloWorldApp
, will simply display the greeting "Hello world!". To create this program, you will:
Create a source file
A source file contains code, written in the Java programming language, that you and other programmers can understand. You can use any text editor to create and edit source files.
Compile the source file into a .class file
The Java programming language compiler (javac
) takes your source file and translates its text into instructions that the Java virtual machine can understand. The instructions contained within this file are known as bytecodes.
Run the program
The Java application launcher tool (java
) uses the Java virtual machine to run your application.
To create a source file, you have two options:
You can save the file
on your computer and avoid a lot of typing. Then, you can go straight to Compile the Source File into a HelloWorldApp.java
.class
File.
Or, you can use the following (longer) instructions.
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. } }
Be Careful When You Type
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:
myapplication
on the C
drive."HelloWorldApp.java"
, without the quotation marks.When you're finished, the dialog box should look like this.
The Save As dialog just before you click Save.
Now click Save, and exit Notepad.
Bring up a shell, or "command," window. You can do this from the Start menu by choosing Run... and then entering cmd
. The shell window should look similar to
the following figure.
A shell window.
The prompt shows your current directory. When you bring up the prompt, your current directory is usually your home directory for Windows XP (as shown in the preceding figure.
To compile your source file, change your current directory to the directory where your file is located. For example, if your source directory is myapplication
on the C
drive, type the following command at the prompt and press Enter:
cd C:\myapplication
Now the prompt should change to C:\myapplication>
.
To change to a directory on a different drive, you must type an extra command: the name of the drive. For example, to change to the myapplication
directory on the D
drive, you must enter D:
, as follows:
C:\>D: D:\>cd myapplication D:\myapplication>
If you enter dir
at the prompt, you should see your source file, as follows:
C:\>cd myapplication C:\myapplication>dir Volume in drive C is System Volume Serial Number is F2E8-C8CC Directory of C:\myapplication 2014-04-24 01:34 PM <DIR> . 2014-04-24 01:34 PM <DIR> .. 2014-04-24 01:34 PM 267 HelloWorldApp.java 1 File(s) 267 bytes 2 Dir(s) 93,297,991,680 bytes free C:\myapplication>
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 follows:
C:\myapplication>javac HelloWorldApp.java C:\myapplication>dir Volume in drive C is System Volume Serial Number is F2E8-C8CC Directory of C:\myapplication 2014-04-24 02:07 PM <DIR> . 2014-04-24 02:07 PM <DIR> .. 2014-04-24 02:07 PM 432 HelloWorldApp.class 2014-04-24 01:34 PM 267 HelloWorldApp.java 2 File(s) 699 bytes 2 Dir(s) 93,298,032,640 bytes free C:\myapplication>
Now that you have a .class
file, you can run your program.
If you encounter problems with the instructions in this step, consult the Common Problems (and Their Solutions).
In the same directory, enter the following command at the prompt:
java -cp . HelloWorldApp
You should see the following on your screen:
C:\myapplication>java -cp . HelloWorldApp Hello World! C:\myapplication>
Congratulations! Your program works!
If you encounter problems with the instructions in this step, consult the Common Problems (and Their Solutions).