import java.awt.*;
import javax.swing.*;
import java.awt.event.*;

public class Jan extends JFrame {
    
    
    private JButton Okbton;
    
    
    public Jan() {
        this.setTitle("Janela");
        this.setSize(300,300);
        this.addWindowListener(new WindowAdapter() {
            public void windowClosing(WindowEvent e) {
                aoFecharJanela();
                
            }
            
            
        });
        
        
        
        this.setLayout(new BorderLayout());
        
        Okbton = new JButton("OK");
        Okbton.addActionListener(new ActionListener(){
            public void actionPerformed(ActionEvent e) {
                JOptionPane.showMessageDialog(null, "Pressionado", "Funcionou!", JOptionPane.WARNING_MESSAGE);
                
            }
            
            
        });
        
        this.add(Okbton, BorderLayout.NORTH);
        this.setVisible(true);
    }
    public static void aoFecharJanela(){
        JOptionPane.showMessageDialog(null, "Janela encerrada!");
        System.exit(0);
    }
    
    public static void main(String [] args) {
        new Jan();
    }
}