I'm new at Java and I have started out with a tutorial... The tutorial wants you to start this way:

```
package proj;
import javax.swing.*;
import java.awt.event.*;
import java.awt.*;

public class Proj extends JFrame implements ActionListener {

   public static void main(String[] args) {

   }

}

```

But I get an error message on the class Proj, that is saying: "Proj is not abstract and does not override abstract method actionPerformed(ActionEvent) in ActionListener".

I don't quite understand what this error message means, and in the tutorial this isn't mentioned.