Run a Java program directly, without using Eclipse

Follow these directions if you’d rather type your Java programs with a familiar application such as Notepad, and run your Java programs from the Windows Command Prompt.

  1. Find the name of the folder that contains the application javac.exe (the Java compiler). On my machine, the folder was C:\Program Files\Java\jdk1.5.0_06\bin. The application java.exe (the Java Virtual Machine) should be in the same directory. 
    start → Search → For Files or Folders… All files and folders → All or part of the file name: javac.exe
Right-click on javac.exe → Open Containing Folder
  2. Put the name of the directory that holds javac.exe and java.exe into the PATH environment variable. This variable contains names of directories, separated by semicolons. 
    Right-click on My Computer → Properties → Advanced → Environment Variables → System variables
Select PATH and press Edit
At the right end of the Variable value,
insert a semicolon and C:\Program Files\Java\jdk1.5.0_06\bin
Press the three OK buttons.
  3. After pressing the three OK buttons, open the Windows Command Prompt. Say PATH to verify that the directory holding javac.exe and java.exe is now in your PATH environment variable. Then go to the C:\ directory, create a subdirectory named myjava, and go there. 
    start → Programs → Accessories → Command Prompt
PATH

    
cd C:\
mkdir myjava
dir

    
cd myjava
dir

    

    4. 


  4. Open your
myjava
folder.

    5. 


    Double-click on My Computer → Local Disk (C:) → myjava

    

Use
Notepad
to create a file named
HelloWorld.java
in the
myjava
folder.
It should contain the following Java program.
If you want to edit this file again,
you’ll have to right-click on it
and select
Open With → Notepad.

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

    



  5. In the command prompt,
verify that the directory
myjava
now contains a file named
HelloWorld.java.
(If the filename ends with
.txt,
use the
RENAME
command to remove the
.txt.
This should not be necessary.)
Run
javac.exe
to create a new file named
HelloWorld.class.


    dir
rename HelloWorld.java.txt HelloWorld.java
dir

    


    javac HelloWorld.java
dir

    

    6. 


  6. Run
java.exe
to execute the
HelloWorld.class
file and send its standard output to the Command Prompt window.
You can also use
>
to save the standard output in a
.txt
file.

    java HelloWorld
Hello, world!

    


    java HelloWorld > HelloWorld.txt
dir

    

    7. 


  7. If your Java program uses the
SWT
(for example,
HelloWorldSWT.java),
download the
swt-….zip
file as in
this step 3
and place it in the
C:\myjava
folder.
Open the
swt-….zip
file with
WinZip,
creating a subdirectory named something like
swt-M20070212-1330-win32-win32-x86.
This subdirectory will contain a file named
swt.jar
as well as several
.dll
files.
Then type the following
javac
and
java
commands.
The
java
command is so long that you might want to split it onto two lines with the
^
character;
you will be prompted with
More?.
The
java.library.path
tells
java
where the
.dll
files are;
see Arnold, Gosling, Holmes, p. 663.


    cd C:\myjava
javac -classpath swt-M20070212-1330-win32-win32-x86\swt.jar HelloWorldSWT.java
dir

    


    java -classpath .;swt-M20070212-1330-win32-win32-x86\swt.jar ^
More? -Djava.library.path=swt-M20070212-1330-win32-win32-x86 HelloWorldSWT

    

Of course, if you move the
swt.jar
file and the
.dll
files up one level into the
C:\myjava
directory,
the
javac
and
java
commands can be simplified to the following.


    cd C:\myjava
javac -classpath swt.jar HelloWorldSWT.java
dir

    


    java -classpath .;swt.jar HelloWorldSWT

    

    8.