Java编写计算器的的常见做法
addButton("5", 1, 3, 1, 1, );
addButton("6", 2, 3, 1, 1, );
addButton("*", 3, 3, 1, 1, command);
addButton("1", 0, 4, 1, 1, );
addButton("2", 1, 4, 1, 1, );
addButton("3", 2, 4, 1, 1, );
addButton("-", 3, 4, 1, 1, command);
addButton("0", 0, 5, 1, 1, );
// addButton("+/-", 1, 5, 1, 1, );// 只显示"-"号,"+"没有实用价值
addButton(".", 2, 5, 1, 1, );
addButton("+", 3, 5, 1, 1, command);
addButton("=", 0, 6, 4, 1, command);
this.setResizable(false);
setSize(180, 200);
setVisible(true);
}
private void addButton(String label, int row, int column, int with,
int height, ActionListener listener) {
JButton button = new JButton(label);
constraints.gridx = row;
constraints.gridy = column;
constraints.gridwidth = with;
constraints.gridheight = height;
constraints.fill = GridBagConstraints.BOTH;
button.addActionListener(listener);
layout.setConstraints(button, constraints);
container.add(button);
}
private class InsertAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String input = event.getActionCommand();
if (start) {
displayField.setText("");
start = false;
if (input.equals("+/-"))
displayField.setText(displayField.getText() + "-");
}
if (!input.equals("+/-")) {
if (input.equals("Backspace")) {
String str = displayField.getText();
if (str.length() > 0)
displayField.setText(str.substring(0, str.length() - 1));
} else if (input.equals("CE") || input.equals("C")) {
displayField.setText("0");
start = true;
} else
displayField.setText(displayField.getText() + input);
}
}
}
private class CommandAction implements ActionListener {
public void actionPerformed(ActionEvent evt) {
String command = evt.getActionCommand();
if (start) {
lastCommand = command;
} else {
calculate(Double.parseDouble(displayField.getText()));
lastCommand = command;
start = true;
}
}
}
public void calculate(double x) {
if (lastCommand.equals("+"))
result += x;
else if (lastCommand.equals("-"))
result -= x;
else if (lastCommand.equals("*"))
result *= x;
else if (lastCommand.equals("/"))
result /= x;
else if (lastCommand.equals("="))
result = x;
displayField.setText("" + result);
}
public static void main(String[] args) {
Calculator calculator = new Calculator();
calculator.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
第四种写法：
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package wanwa;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
public class Calculator extends JFrame {
private Container container;
private GridBagLayout layout;
private GridBagConstraints constraints;
private JTextField displayField;// 计算结果显示区
private String lastCommand;// 保存+,-,*,/,=命令
private double result;// 保存计算结果
private boolean start;// 判断是否为数字的开始
public Calculator() {
super("Calculator");
container = getContentPane();
layout = new GridBagLayout();
container.setLayout(layout);
constraints = new GridBagConstraints();
start = true;
result = 0;
lastCommand = "=";
displayField = new JTextField(20);
displayField.setHorizontalAlignment(JTextField.RIGHT);
constraints.gridx = 0;
constraints.gridy = 0;
constraints.gridwidth = 4;
constraints.gridheight = 1;
constraints.fill = GridBagConstraints.BOTH;
constraints.weightx = 100;
constraints.weighty = 100;
layout.setConstraints(displayField, constraints);
container.add(displayField);
ActionListener = new InsertAction();
ActionListener command = new CommandAction();
// addButton("Backspace", 0, 1, 2, 1, );
// addButton("CE", 2, 1, 1, 1, );
// addButton("C", 3, 1, 1, 1, );
addButton("7", 0, 2, 1, 1, );
addButton("8", 1, 2, 1, 1, );
addButton("9", 2, 2, 1, 1, );
addButton("/", 3, 2, 1, 1, command);
addButton("4", 0, 3, 1, 1, );
addButton("5", 1, 3, 1, 1, );
addButton("6", 2, 3, 1, 1, );
addButton("*", 3, 3, 1, 1, command);
addButton("1", 0, 4, 1, 1, );
addButton("2", 1, 4, 1, 1, );
addButton("3", 2, 4, 1, 1, );
addButton("-", 3, 4, 1, 1, command);
addButton("0", 0, 5, 1, 1, );
// addButton("+/-", 1, 5, 1, 1, );// 只显示"-"号,"+"没有实用价值
addButton(".", 2, 5, 1, 1, );
addButton("+", 3, 5, 1, 1, command);
addButton("=", 0, 6, 4, 1, command);
this.setResizable(false);
setSize(180, 200);
setVisible(true);
}
private void addButton(String label, int row, int column, int with,
int height, ActionListener listener) {
JButton button = new JButton(label);
constraints.gridx = row;
constraints.gridy = column;
constraints.gridwidth = with;
constraints.gridheight = height;
constraints.fill = GridBagConstraints.BOTH;
button.addActionListener(listener);
layout.setConstraints(button, constraints);
container.add(button);
}
private class InsertAction implements ActionListener {
public void actionPerformed(ActionEvent event) {
String input = event.getActionCommand();
if (start) {
displayField.setText("");
start = false;
if (input.equals("+/-"))
displayField.setText(displayField.getText() + "-");
}
if (!input.equals("+/-")) {
if (input.equals("Backspace")) {
String str = displayField.getText();
if (str.length() > 0)
displayField.setText(str.substring(0, str.length() - 1));
} else if (input.equals("CE") || input.equals("C")) {
displayField.setText("0");
start = true;
} else
displayField.setText(displayField.getText() + input);
}
}
}
private class CommandAction implements ActionListener {
public void actionPerformed(ActionEvent evt) {
String command = evt.getActionCommand();
if (start) {
lastCommand = command;
} else {
calculate(Double.parseDouble(displayField.getText()));
lastCommand = command;
start = true;
}
}
}
public void calculate(double x) {
if (lastCommand.equals("+"))
result += x;
else if (lastCommand.equals("-"))
result -= x;
else if (lastCommand.equals("*"))
result *= x;
else if (lastCommand.equals("/"))
result /= x;
else if (lastCommand.equals("="))
result = x;
displayField.setText("" + result);
}
public static void main(String[] args) {
Calculator calculator = new Calculator();
calculator.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
}
}
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