nested type cannot hide an enclosing type

What does this error mean?

The nested type HelloWorld cannot hide an enclosing type

Where HelloWorld is the java file name. Here's the code if you need it:

import net.java.games.jogl.*;
public class HelloWorld
{ // open HelloWorld

    public class HelloWorld
    { // open HelloWorld

        public static void main (String args[])
        { // open main
            try
            { // open try
                System.loadLibrary("jogl");
                System.out.println("Hello World! (The native libraries are installed.)");
            } // close try
            catch (Exception e) // all try's need a catch
            { } // even if the catch does nothing
        } // close main

    } // close HelloWorld

);

You have defined the HelloWorld class twice. Remove one level and you should be fine.

You're declaring the HelloWorld class twice.