java 计算器

简介

java 计算器

code

/*
 * @Author: your name
 * @Date: 2020-10-31 14:47:11
 * @LastEditTime: 2020-10-31 17:05:14
 * @LastEditors: Please set LastEditors
 * @Description: In User Settings Edit
 * @FilePath: /java/calcu/calculatePanel.java
 */
package calcu;

import java.awt.*;
import java.awt.event.*;

import javax.swing.*;

public class CalculatePanel extends JPanel {
    private JButton display;
    private JPanel panel;
    private double result;
    private String lastCommand;
    private boolean start;

    public static void main(String[] args) {
        EventQueue.invokeLater(() -> {
            JFrame m = new JFrame("第一个Java窗口");
            m.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            m.getContentPane().add(new CalculatePanel());
            m.pack();
            m.setVisible(true);
        });
    }

    public CalculatePanel() {
        setLayout(new BorderLayout());

        result = 0;
        lastCommand = "=";
        start = true;

        // add the display
        display = new JButton("0");
        display.setEnabled(false);
        add(display, BorderLayout.NORTH);

        ActionListener insert = new InsertAction();
        ActionListener command = new CommandAction();
        // add the buttons in a 4 * 4 grid

        panel = new JPanel();
        panel.setLayout(new GridLayout(4, 4));

        addButton("7", insert);
        addButton("8", insert);
        addButton("9", insert);
        addButton("/", command);

        addButton("4", insert);
        addButton("5", insert);
        addButton("6", insert);
        addButton("*", command);

        addButton("1", insert);
        addButton("2", insert);
        addButton("3", insert);
        addButton("-", command);

        addButton("0", insert);
        addButton(".", insert);
        addButton("=", command);
        addButton("+", command);

        add(panel, BorderLayout.CENTER);
    }

    private void addButton(String label, ActionListener listener) {
        JButton button = new JButton(label);
        button.addActionListener(listener);
        panel.add(button);
    }

    private class InsertAction implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            String input = event.getActionCommand();
            if (start) {
                display.setText("");
                start = false;
            }
            display.setText(display.getText() + input);
        }
    }

    private class CommandAction implements ActionListener {
        public void actionPerformed(ActionEvent event) {
            String command = event.getActionCommand();

            if (start) {
                if (command.equals("-")) {
                    display.setText(command);
                    start = false;
                } else {
                    lastCommand = command;
                }
            } else {
                calculate(Double.parseDouble(display.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;
        display.setText("" + result);
    }
}