calculadora suma de dos numero

package ejercicios;

import java.awt.FlowLayout;
import java.awt.event.KeyEvent;
import java.awt.event.KeyListener;

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;

public class Capitulo33Calculadora  extends JFrame implements KeyListener{
private JTextField texto;
private JLabel label;

public Capitulo33Calculadora()
{
super("Calculadora(cuma de 2 numeros)");
setLayout(new FlowLayout());
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setSize(400,400);

texto=new JTextField(20);
label=new JLabel();
add(texto);
add(label);

texto.addKeyListener(this);
setVisible(true);
}
@Override
public void keyPressed(KeyEvent e) {
// TODO Auto-generated method stub
if(e.getKeyCode()==KeyEvent.VK_ENTER){
String linea=texto.getText();
int numa=Integer.parseInt(linea.substring(0,linea.indexOf("+")));//decuelve los valores que encuentre hasta toparse con el mas
int numb=Integer.parseInt(linea.substring(linea.indexOf("+")+1,linea.length()));
label.setText(String.valueOf(numa+numb));
}
}

@Override
public void keyReleased(KeyEvent arg0) {
// TODO Auto-generated method stub

}

@Override
public void keyTyped(KeyEvent arg0) {
// TODO Auto-generated method stub

}
public static void main(String[] args) {
new Capitulo33Calculadora();
}

}