CalcPanel.java

package com.devious.calculator;

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

import java.util.*;

public class CalcPanel

extends JPanel

implements ActionListener, Observer

{

private CalcModel model;

private JLabel display = new JLabel("0");

public CalcPanel(CalcModel model)

{

super();

this.model = model;

model.addObserver(this);

}

protected JButton addButton(String label)

{

JButton b = new JButton(label);

b.addActionListener(this);

return b;

}

protected JPanel createButtonPanel()

{

JPanel panel = new JPanel();

panel.setLayout(new GridLayout(0, 4));

panel.add(addButton("1"));

panel.add(addButton("2"));

panel.add(addButton("3"));

panel.add(addButton("+"));

panel.add(addButton("4"));

panel.add(addButton("5"));

panel.add(addButton("6"));

panel.add(addButton("-"));

panel.add(addButton("7"));

panel.add(addButton("8"));

panel.add(addButton("9"));

panel.add(addButton("*"));

panel.add(addButton("C"));

panel.add(addButton("0"));

panel.add(addButton("="));

panel.add(addButton("/"));

return panel;

}

public void init()

{

this.setLayout(new BorderLayout());

display.setVerticalTextPosition(JLabel.CENTER);

display.setHorizontalTextPosition(JLabel.RIGHT);

display.setVerticalAlignment(JLabel.TOP);

display.setHorizontalAlignment(JLabel.TRAILING);

display.setBorder(BorderFactory.createLineBorder(Color.black));

this.add(display, BorderLayout.NORTH);

this.add(createButtonPanel(), BorderLayout.CENTER);

}

public void actionPerformed(ActionEvent evt)

{

System.out.println(evt.paramString());

try {

switch (evt.getActionCommand().charAt(0)) {

case '+':

model.setOperation(CalcModel.OP_ADD);

break;

case '-':

model.setOperation(CalcModel.OP_SUB);

break;

case '*':

model.setOperation(CalcModel.OP_MUL);

break;

case '/':

model.setOperation(CalcModel.OP_DIV);

break;

case '=':

model.calculate();

break;

case 'C':

model.clear();

break;

default:

model.addDigit(evt.getActionCommand());

break;

}

} catch (NumberFormatException ex) {}

}

public void update(Observable o, Object arg)

{

display.setText(model.getValue());

}

}

Далее создаем файл