public class Main {
	public static void main(String[] args) {
		RepositorioTarea repositorioTarea = new RepositorioTarea();
		ServicioTarea servicioTarea = new ServicioTarea(repositorioTarea);
		FrmPrincipal frmPrincipal = new FrmPrincipal(servicioTarea);
		frmPrincipal.setVisible(true);
	}
}
 
 

import java.awt.BorderLayout;
 
public class FrmPrincipal extends JFrame {
 
	private static final long serialVersionUID = 1L;
	private JPanel contentPane;
	private JTextField txtTareaNombre;
	private JTable table;
 
	private ServicioTarea servicioTarea;
 
	public FrmPrincipal(ServicioTarea servicioTarea) {
		this.servicioTarea = servicioTarea;
		init();
	}
 
	public static void main(String[] args) {
		EventQueue.invokeLater(new Runnable() {
			public void run() {
				try {
					FrmPrincipal frame = new FrmPrincipal();
					frame.setVisible(true);
				} catch (Exception e) {
					e.printStackTrace();
				}
			}
		});
	}
 
	/**
	 * Create the frame.
	 */
	public FrmPrincipal() {
		init();
	}
 
	private void init() {
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		setBounds(100, 100, 450, 300);
		contentPane = new JPanel();
		contentPane.setBorder(new EmptyBorder(5, 5, 5, 5));
		contentPane.setLayout(new BorderLayout(0, 0));
		setContentPane(contentPane);
 
		JPanel panel = new JPanel();
		contentPane.add(panel, BorderLayout.NORTH);
		panel.setLayout(new FlowLayout(FlowLayout.CENTER, 5, 5));
 
		JLabel lblNewLabel = new JLabel("Tarea");
		panel.add(lblNewLabel);
 
		txtTareaNombre = new JTextField();
		panel.add(txtTareaNombre);
		txtTareaNombre.setColumns(10);
 
		JButton btnAgrega = new JButton("agrega");
 
		panel.add(btnAgrega);
 
		JScrollPane scrollPane = new JScrollPane();
		contentPane.add(scrollPane, BorderLayout.CENTER);
 
		table = new JTable();
		scrollPane.setViewportView(table);
		table.setModel(new DefaultTableModel(new Object[][] {}, new String[] {
				"Codigo", "Descripcion", "fecha" }));
		btnAgrega.addActionListener(new ActionListener() {
			public void actionPerformed(ActionEvent e) {
				servicioTarea.agregar(new Tarea(null, txtTareaNombre.getText(),
						null));
 
				List<Tarea> tareas = servicioTarea.tareas();
				DefaultTableModel defaultTableModel = (DefaultTableModel) table
						.getModel();
				defaultTableModel.setRowCount(0);
				for (Tarea tarea : tareas) {
					defaultTableModel.addRow(new Object[] { tarea.getId(),
							tarea.getNombre(), tarea.getDate() });
				}
			}
		});
	}
 
}
 

import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
 
public class RepositorioTarea {
	private HashMap<Integer, Tarea> hashMap = new HashMap<>();
 
	public void agregar(Tarea tarea) {
		int size = hashMap.size();
		hashMap.put(size + 1,
				new Tarea(size + 1, tarea.getNombre(), tarea.getDate()));
	}
 
	public List<Tarea> listar() {
		ArrayList<Tarea> respuesta = new ArrayList<>();
		Collection<Tarea> values = hashMap.values();
		for (Tarea tarea : values) {
			respuesta.add(new Tarea(tarea.getId(), tarea.getNombre(), tarea
					.getDate()));
		}
		return respuesta;
	}
 
}
 

import java.util.Date;
import java.util.List;
 
public class ServicioTarea {
 
	private final RepositorioTarea repositorioTarea;
 
	public ServicioTarea(RepositorioTarea repositorioTarea) {
		this.repositorioTarea = repositorioTarea;
	}
 
	public void agregar(Tarea tarea) {
		tarea.setDate(new Date());
		repositorioTarea.agregar(tarea);
	}
 
	public List<Tarea> tareas() {
		return repositorioTarea.listar();
	}
}
 

import java.util.Date;
 
public class Tarea {
	private Integer id;
	private String nombre;
	private Date date;
 
	public Tarea(Integer id, String nombre, Date date) {
		this.id = id;
		this.nombre = nombre;
		this.date = date;
	}
 
	public Integer getId() {
		return id;
	}
 
	public void setId(Integer id) {
		this.id = id;
	}
 
	public String getNombre() {
		return nombre;
	}
 
	public void setNombre(String nombre) {
		this.nombre = nombre;
	}
 
	public Date getDate() {
		return date;
	}
 
	public void setDate(Date date) {
		this.date = date;
	}
 
}