Interface Gráfica + Eventos + Expressões regulares para validar Email

import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JTextField;
import javax.swing.JButton;
import javax.swing.JOptionPane;
import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.FocusAdapter;
import java.awt.event.FocusEvent;
import java.util.regex.Pattern;
import java.util.regex.Matcher;

/**
*Classe que faz a validação de email,utilizando do se de 
*swing
*/

public class Email extends JFrame implements ActionListener {

private JLabel l1;
private JTextField t1;
private JButton b1;
private Pattern pattern;
private Matcher matcher;

public Email(){

//Configurando o JFrame
setTitle("Validação de Email");
setSize(430,100);
setLocation(180,210);
getContentPane().setLayout(null);

//Instanciando e Configurando o JLabel
l1 = new JLabel("Informe o Email");
l1.setBounds(40,10,125,25);

//Instanciando e Configurando o JTextField
t1=new JTextField();
t1.setBounds(165,10,225,25);
t1.addFocusListener(new FocusAdapter() {
public void focusLost(FocusEvent e){
Pattern pattern = Pattern.compile("[a-z_][a-z0-9._]+@.+\\.[a-z]+");
Matcher matcher = pattern.matcher(t1.getText());
if(matcher.matches()){
JOptionPane.showMessageDialog(null,"Email Válido","INFORMANDO",JOptionPane.INFORMATION_MESSAGE);
}
else {
JOptionPane.showMessageDialog(null,"Email Incorreto","ERRO",JOptionPane.ERROR_MESSAGE);
t1.setText("");
t1.requestFocus();
}
}
});

//Instanciando e Configurando a JButton
b1 = new JButton("Enviar Email");
b1.setBounds(145,40,95,25);
b1.addActionListener(this);

//Inserindo os Objetos no container
getContentPane().add(l1);
getContentPane().add(t1);
getContentPane().add(b1);

}

public void actionPerformed(ActionEvent e){

if(e.getSource().equals(b1)){
 if(t1.getText().equals("")){
JOptionPane.showMessageDialog(null,"Campo em Branco","ERRO",JOptionPane.WARNING_MESSAGE);
}
else {
JOptionPane.showMessageDialog(null,"Enviando Email","INFORMANDO",JOptionPane.INFORMATION_MESSAGE);
t1.setText("");
}
}
}

public static void main(String args[]){
Email email = new Email();
email.setVisible(true);
email.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}