计算器

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class JCalculator extends JFrame implements ActionListener {

private static final long serialVersionUID = -169068472193786457L;

private class WindowCloser extends WindowAdapter {

public void windowClosing(WindowEvent we) {

System.exit(0);

}

}

int i;

// Strings for Digit & Operator buttons.

private final String[] str = { "7", "8", "9", "/", "4", "5", "6", "*","1",

"2", "3", "-", ".", "0", "=", "+" };

// Build buttons.

JButton[] buttons = new JButton[str.length];

// For cancel or reset.

JButton reset = new JButton("CE");

// Build the text field to show the result.

JTextField display = new JTextField("0");

public JCalculator() {

super("Calculator");

// Add a panel.

JPanel panel1 = new JPanel(new GridLayout(4, 4));

// panel1.setLayout(new GridLayout(4,4));

for (i = 0; i < str.length; i++) {

buttons[i] = new JButton(str[i]);

panel1.add(buttons[i]);

}

JPanel panel2 = new JPanel(new BorderLayout());

// panel2.setLayout(new BorderLayout());

panel2.add("Center", display);

panel2.add("East", reset);

// JPanel panel3 = new Panel();

getContentPane().setLayout(new BorderLayout());

getContentPane().add("North", panel2);

getContentPane().add("Center", panel1);

// Add action listener for each digit & operator button.

for (i = 0; i < str.length; i++)

buttons[i].addActionListener(this);

// Add listener for "reset" button.

reset.addActionListener(this);

// Add listener for "display" button.

display.addActionListener(this);

// The "close" button "X".

addWindowListener(new WindowCloser());

// Initialize the window size.

setSize(800, 800);

// Show the window.

// show(); Using show() while JDK version is below 1.5.

setVisible(true);

// Fit the certain size.

pack();

}

public void actionPerformed(ActionEvent e) {

Object target = e.getSource();

String label = e.getActionCommand();

if (target == reset)

handleReset();

else if ("0123456789.".indexOf(label) > 0)

handleNumber(label);

else

handleOperator(label);

}

// Is the first digit pressed?

boolean isFirstDigit = true;

public void handleNumber(String key) {

if (isFirstDigit)

display.setText(key);

else if ((key.equals(".")) && (display.getText().indexOf(".") < 0))

display.setText(display.getText() + ".");

else if (!key.equals("."))

display.setText(display.getText() + key);

isFirstDigit = false;

}

public void handleReset() {

display.setText("0");

isFirstDigit = true;

operator = "=";

}

double number = 0.0;

String operator = "=";

public void handleOperator(String key) {

if (operator.equals("+"))

number += Double.valueOf(display.getText());

else if (operator.equals("-"))

number -= Double.valueOf(display.getText());

else if (operator.equals("*"))

number *= Double.valueOf(display.getText());

else if (operator.equals("/"))

number /= Double.valueOf(display.getText());

else if (operator.equals("="))

number = Double.valueOf(display.getText());

display.setText(String.valueOf(number));

operator = key;

isFirstDigit = true;

}

public static void main(String[] args) {

new JCalculator();

}

}