Ajuda com janelas

estou precisando de uma ajuda com esse programa…
eu queria colocar um funcionabilidad nele mas nao consigo
colocar q funcione depois q digitar as medias espero contar com ajuda de vs
obrigado

import javax.swing.;
import java.awt.;

class media extends JFrame
{

JPanel principal = new JPanel();

JTextField nota1;

JTextField nota2;

JTextField nota3;

JTextField media;

JButton calcular;

JButton limpar;

JButton sair;

public media()

{

setDefaultCloseOperation(EXIT_ON_CLOSE);

setBounds(220,200,280,200);

principal = new JPanel();
principal.setLayout(new GridLayout(4,3,6,);

nota1 = new JTextField(" “);

nota2 = new JTextField(” “);

nota3 = new JTextField(” “);

media = new JTextField(” ");

nota1.add(new JLabel(“Nota 1”));
nota1.add(new JTextField(150));

nota2.add(new JLabel(“Nota 2”));
nota2.add(new JTextField(150));

nota3.add(new JLabel(“Nota 3”));
nota3.add(new JTextField(150));

media.add(new JLabel(“Media”));
media.add(new JTextField(150));

//==========================================//

//principal.add(saida);

principal.setBorder(BorderFactory.createEtchedBorder());

getContentPane().add(principal, BorderLayout.CENTER);

principal = new JPanel();
principal.setLayout(new FlowLayout());

principal.add(new JButton(“Calcular”));

principal.add(new JButton(“Limpar”));

principal.add(new JButton(“Sair”));

// principal.setBorder(BorderFactory.createEtchedBorder());

getContentPane().add(principal, BorderLayout.SOUTH);

/* sair.addActionListener(new ActionListener()

{

public void actionPerformed(ActionEvent e) {

System.exit(0); //Fechar aplicação

}

});*/

this.setVisible(true);

}

public static void main(String args[])

{

// media = new media(“Media”);

(new media()).show();

}
}