用Java实现计算器，CE键为清除，C键为清除全部，M+，M-,MR,MC其中M+为讲当前显示的存储数值进行加法运算，Backspace为退格键，含有单目运算：+/1丶1/x丶sqrt丶%等。双目运算符有+丶-丶*丶/

以下是用 Java 实现的简单计算器，包含CE、C、M+、M-、MR、MC等功能。

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Calculator extends JFrame implements ActionListener {
    private JButton button0, button1, button2, button3, button4, button5, button6, button7, button8, button9;
    private JButton buttonCE, buttonC, buttonMPlus, buttonMMinus, buttonMR, buttonMC;
    private JButton buttonPlus, buttonMinus, buttonMultiply, buttonDivide, buttonEqual, buttonDot, buttonBackspace;
    private JButton buttonSquareRoot, buttonReciprocal, buttonNegate, buttonPercentage;

    private JTextField textField;

    private double memory = 0;
    private String operator = "";
    private boolean isOperatorClicked = false;
    private boolean isDotClicked = false;

    public Calculator() {
        setTitle("Calculator");
        setSize(280, 300);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        textField = new JTextField();
        textField.setEditable(false);
        textField.setHorizontalAlignment(JTextField.RIGHT);

        button0 = new JButton("0");
        button1 = new JButton("1");
        button2 = new JButton("2");
        button3 = new JButton("3");
        button4 = new JButton("4");
        button5 = new JButton("5");
        button6 = new JButton("6");
        button7 = new JButton("7");
        button8 = new JButton("8");
        button9 = new JButton("9");

        buttonCE = new JButton("CE");
        buttonC = new JButton("C");
        buttonMPlus = new JButton("M+");
        buttonMMinus = new JButton("M-");
        buttonMR = new JButton("MR");
        buttonMC = new JButton("MC");

        buttonPlus = new JButton("+");
        buttonMinus = new JButton("-");
        buttonMultiply = new JButton("*");
        buttonDivide = new JButton("/");
        buttonEqual = new JButton("=");
        buttonDot = new JButton(".");
        buttonBackspace = new JButton("<-");

        buttonSquareRoot = new JButton("sqrt");
        buttonReciprocal = new JButton("1/x");
        buttonNegate = new JButton("+/-");
        buttonPercentage = new JButton("%");

        button0.addActionListener(this);
        button1.addActionListener(this);
        button2.addActionListener(this);
        button3.addActionListener(this);
        button4.addActionListener(this);
        button5.addActionListener(this);
        button6.addActionListener(this);
        button7.addActionListener(this);
        button8.addActionListener(this);
        button9.addActionListener(this);

        buttonCE.addActionListener(this);
        buttonC.addActionListener(this);
        buttonMPlus.addActionListener(this);
        buttonMMinus.addActionListener(this);
        buttonMR.addActionListener(this);
        buttonMC.addActionListener(this);

        buttonPlus.addActionListener(this);
        buttonMinus.addActionListener(this);
        buttonMultiply.addActionListener(this);
        buttonDivide.addActionListener(this);
        buttonEqual.addActionListener(this);
        buttonDot.addActionListener(this);
        buttonBackspace.addActionListener(this);

        buttonSquareRoot.addActionListener(this);
        buttonReciprocal.addActionListener(this);
        buttonNegate.addActionListener(this);
        buttonPercentage.addActionListener(this);

        JPanel panel1 = new JPanel(new GridLayout(1, 1));
        panel1.add(textField);

        JPanel panel2 = new JPanel(new GridLayout(4, 5));
        panel2.add(buttonCE);
        panel2.add(buttonC);
        panel2.add(buttonMPlus);
        panel2.add(buttonMMinus);
        panel2.add(buttonMR);
        panel2.add(button7);
        panel2.add(button8);
        panel2.add(button9);
        panel2.add(buttonDivide);
        panel2.add(buttonSquareRoot);
        panel2.add(button4);
        panel2.add(button5);
        panel2.add(button6);
        panel2.add(buttonMultiply);
        panel2.add(buttonReciprocal);
        panel2.add(button1);
        panel2.add(button2);
        panel2.add(button3);
        panel2.add(buttonMinus);
        panel2.add(buttonPercentage);
        panel2.add(buttonNegate);
        panel2.add(button0);
        panel2.add(buttonDot);
        panel2.add(buttonBackspace);
        panel2.add(buttonPlus);
        panel2.add(buttonEqual);

        JPanel contentPane = new JPanel(new BorderLayout());
        contentPane.add(panel1, BorderLayout.NORTH);
        contentPane.add(panel2, BorderLayout.CENTER);

        setContentPane(contentPane);
        setVisible(true);
    }

    public void actionPerformed(ActionEvent e) {
        if (e.getSource() == button0) {
            textField.setText(textField.getText() + "0");
        } else if (e.getSource() == button1) {
            textField.setText(textField.getText() + "1");
        } else if (e.getSource() == button2) {
            textField.setText(textField.getText() + "2");
        } else if (e.getSource() == button3) {
            textField.setText(textField.getText() + "3");
        } else if (e.getSource() == button4) {
            textField.setText(textField.getText() + "4");
        } else if (e.getSource() == button5) {
            textField.setText(textField.getText() + "5");
        } else if (e.getSource() == button6) {
            textField.setText(textField.getText() + "6");
        } else if (e.getSource() == button7) {
            textField.setText(textField.getText() + "7");
        } else if (e.getSource() == button8) {
            textField.setText(textField.getText() + "8");
        } else if (e.getSource() == button9) {
            textField.setText(textField.getText() + "9");
        } else if (e.getSource() == buttonCE) {
            textField.setText("");
            isDotClicked = false;
        } else if (e.getSource() == buttonC) {
            textField.setText("");
            memory = 0;
            operator = "";
            isOperatorClicked = false;
            isDotClicked = false;
        } else if (e.getSource() == buttonMPlus) {
            memory = memory + Double.parseDouble(textField.getText());
            isDotClicked = false;
        } else if (e.getSource() == buttonMMinus) {
            memory = memory - Double.parseDouble(textField.getText());
            isDotClicked = false;
        } else if (e.getSource() == buttonMR) {
            textField.setText(Double.toString(memory));
            isDotClicked = false;
        } else if (e.getSource() == buttonMC) {
            memory = 0;
            isDotClicked = false;
        } else if (e.getSource() == buttonPlus) {
            if (!isOperatorClicked) {
                memory = Double.parseDouble(textField.getText());
                isDotClicked = false;
            } else {
                memory = calculate(memory, operator, Double.parseDouble(textField.getText()));
                textField.setText(Double.toString(memory));
                isDotClicked = false;
            }
            operator = "+";
            isOperatorClicked = true;
        } else if (e.getSource() == buttonMinus) {
            if (!isOperatorClicked) {
                memory = Double.parseDouble(textField.getText());
                isDotClicked = false;
            } else {
                memory = calculate(memory, operator, Double.parseDouble(textField.getText()));
                textField.setText(Double.toString(memory));
                isDotClicked = false;
            }
            operator = "-";
            isOperatorClicked = true;
        } else if (e.getSource() == buttonMultiply) {
            if (!isOperatorClicked) {
                memory = Double.parseDouble(textField.getText());
                isDotClicked = false;
            } else {
                memory = calculate(memory, operator, Double.parseDouble(textField.getText()));
                textField.setText(Double.toString(memory));
                isDotClicked = false;
            }
            operator = "*";
            isOperatorClicked = true;
        } else if (e.getSource() == buttonDivide) {
            if (!isOperatorClicked) {
                memory = Double.parseDouble(textField.getText());
                isDotClicked = false;
            } else {
                memory = calculate(memory, operator, Double.parseDouble(textField.getText()));
                textField.setText(Double.toString(memory));
                isDotClicked = false;
            }
            operator = "/";
            isOperatorClicked = true;
        } else if (e.getSource() == buttonEqual) {
            memory = calculate(memory, operator, Double.parseDouble(textField.getText()));
            textField.setText(Double.toString(memory));
            operator = "";
            isOperatorClicked = false;
            isDotClicked = false;
        } else if (e.getSource() == buttonDot) {
            if (!isDotClicked) {
                textField.setText(textField.getText() + ".");
                isDotClicked = true;
            }
        } else if (e.getSource() == buttonBackspace) {
            String text = textField.getText();
            if (text.length() > 0) {
                text = text.substring(0, text.length() - 1);
                textField.setText(text);
            }
            isDotClicked = text.contains(".");
        } else if (e.getSource() == buttonSquareRoot) {
            double value = Double.parseDouble(textField.getText());
            textField.setText(Double.toString(Math.sqrt(value)));
            isDotClicked = false;
        } else if (e.getSource() == buttonReciprocal) {
            double value = Double.parseDouble(textField.getText());
            textField.setText(Double.toString(1 / value));
            isDotClicked = false;
        } else if (e.getSource() == buttonNegate) {
            double value = Double.parseDouble(textField.getText());
            textField.setText(Double.toString(-value));
            isDotClicked = false;
        } else if (e.getSource() == buttonPercentage) {
            double value = Double.parseDouble(textField.getText());
            textField.setText(Double.toString(value / 100));
            isDotClicked = false;
        }
    }

    private double calculate(double operand1, String operator, double operand2) {
        if (operator.equals("+")) {
            return operand1 + operand2;
        } else if (operator.equals("-")) {
            return operand1 - operand2;
        } else if (operator.equals("*")) {
            return operand1 * operand2;
        } else if (operator.equals("/")) {
            return operand1 / operand2;
        }
        return operand2;
    }

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

运行效果如下：