Im learning java, and i build a simple applet...
I compiled it into *.class and now, when i run it, i got the following
error:

Exception in thread "main" java.lang.NoSuchMethodError: main

How can i fix this? the code of the applet is this:

import java.awt.*;

public class RootApplet extends javax.swing.JApplet {
   int number;

   public void init() {
       number = 225;
   }

   public void paint(Graphics screen) {
       Graphics2D screen2D = (Graphics2D) screen;
       screen2D.drawString("the square root of " +
           number +
           " is " +
           Math.sqrt(number), 5, 50);
   }
}

I hope some1 can help me