C:Usersoreyessamplesjavacreate-jar>type HelloWorldSwing.java
    package start;

    import javax.swing.*;

    public class HelloWorldSwing {
        public static void main(String[] args) {
            //Create and set up the window.
            JFrame frame = new JFrame("HelloWorldSwing");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

            JLabel label = new JLabel("Hello World");
            frame.add(label);

            //Display the window.
            frame.pack();
            frame.setVisible(true);
        }
    }
    class Dummy {
        // just to have another thing to pack in the jar
    }

C:Usersoreyessamplesjavacreate-jar>javac -d . HelloWorldSwing.java

C:Usersoreyessamplesjavacreate-jar>dir start

 Directorio de C:Usersoreyessamplesjavacreate-jarstart

29/04/2009  06:56 p.m.    <DIR>          .
29/04/2009  06:56 p.m.    <DIR>          ..
29/04/2009  06:58 p.m.               200 Dummy.class
29/04/2009  06:58 p.m.               622 HelloWorldSwing.class
               2 archivos            822 bytes

C:Usersoreyessamplesjavacreate-jar>type manifest.mf
Main-class: start.HelloWorldSwing

C:Usersoreyessamplesjavacreate-jar>jar -cmf manifest.mf hello.jar start

java YourClass

jar -cvf [name of jar file] [name of directory with Java files]

Main-Class: [fully qualified name of your main class]

java -jar [name of jar file]