Compliling Issue

Any help would be appreciated. I have a compiling problem.

When I try to compile this:

import javax.swing.JOptionPane;
public class FirstDialog
{
public static void main(String[] args)
{
JOptionPane.showMessageDialog(null, "First Java dialog");
}
}

I get this:

public class FirstDialog
^

As my error.

I copy and pasted right from my ebook text book so I don't see what the error could be.

Any help please?