简单计算器实现

基本思路:边输入边计算，最后显示

import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javafx.scene.layout.Border;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;

public class Calculator extends JFrame {
private boolean start, flag;
private String lastCommand;
private double result1, result2;
private int count=1;
JButton display;
JPanel panel;

public Calculator() {
    setLayout(new BorderLayout());
    result1 = 0;
    result2 = 0;
    start = true;
    flag = false;
    lastCommand = "=";

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

    ActionListener insert = new InsertAction();
    ActionListener command = new CommandListener();
    panel = new JPanel(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);

    pack();
    setTitle("Calculator");
    setResizable(false);
    setSize(300, 200);
    setLocation(400, 400);
    setVisible(true);
    setDefaultCloseOperation(this.EXIT_ON_CLOSE);
}

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

private class InsertAction implements ActionListener {// 监听数字按钮

    public void actionPerformed(ActionEvent e) {

        String input = e.getActionCommand();
        display.setText(display.getText() + input);
    }
}

private class CommandListener implements ActionListener {// 监听命令按钮

    public void actionPerformed(ActionEvent e) {

        String command = e.getActionCommand();
        if (flag) {
            String[] s;
            s = display.getText().split("\\" + lastCommand);
            result2 = Double.parseDouble(s[s.length-1]);
            System.out.println(result2);
            calculator();
            if (command.equals("="))
                display.setText("" + result1);
            else
                display.setText(display.getText() + command);

            lastCommand = command;
            //flag = false;
        } else {
            result1 = Double.parseDouble(display.getText());
            display.setText(display.getText() + command);
            lastCommand = command;
            flag = true;
        }
    }
}

public void calculator() {// 进行计算的函数

    if (lastCommand.equals("+")) {
        result1 += result2;
    } else if (lastCommand.equals("-")) {
        result1 -= result2;
    } else if (lastCommand.equals("*")) {
        result1 *= result2;
    } else if (lastCommand.equals("/")) {
        result1 /= result2;
    } else if (lastCommand.equals("=")) {
        result1 = result2;
    }
}

public static void main(String[] args) {
    new Calculator();
}

}