用Java实现实现计算器，backspace为退格键，单目运算符：+/-，1/x，sqrt，%双目运算符：+，-，*，/。CE为清除，C为清除全部，M+，M-,MR,MC,M+表示将当前显示的存储数值进行加法运算

以下是一个简单的Java计算器实现，包括上述要求的功能：

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

public class Calculator extends JFrame implements ActionListener {

    private static final long serialVersionUID = 1L;

    private JButton display;
    private JButton backspace;
    private JButton plusMinus;
    private JButton reciprocal;
    private JButton squareRoot;
    private JButton percent;
    private JButton clearEntry;
    private JButton clearAll;
    private JButton memoryPlus;
    private JButton memoryMinus;
    private JButton memoryRecall;
    private JButton memoryClear;
    private JButton divide;
    private JButton multiply;
    private JButton subtract;
    private JButton add;
    private JButton equals;

    private double memory = 0;
    private double currentNumber = 0;
    private double result = 0;
    private char lastOperator;

    private boolean startNewNumber = true;

    public Calculator() {
        super("Calculator");

        display = new JButton("0");
        display.setEnabled(false);
        backspace = new JButton("Backspace");
        backspace.addActionListener(this);
        plusMinus = new JButton("+/-");
        plusMinus.addActionListener(this);
        reciprocal = new JButton("1/x");
        reciprocal.addActionListener(this);
        squareRoot = new JButton("sqrt");
        squareRoot.addActionListener(this);
        percent = new JButton("%");
        percent.addActionListener(this);
        clearEntry = new JButton("CE");
        clearEntry.addActionListener(this);
        clearAll = new JButton("C");
        clearAll.addActionListener(this);
        memoryPlus = new JButton("M+");
        memoryPlus.addActionListener(this);
        memoryMinus = new JButton("M-");
        memoryMinus.addActionListener(this);
        memoryRecall = new JButton("MR");
        memoryRecall.addActionListener(this);
        memoryClear = new JButton("MC");
        memoryClear.addActionListener(this);
        divide = new JButton("/");
        divide.addActionListener(this);
        multiply = new JButton("*");
        multiply.addActionListener(this);
        subtract = new JButton("-");
        subtract.addActionListener(this);
        add = new JButton("+");
        add.addActionListener(this);
        equals = new JButton("=");
        equals.addActionListener(this);

        JPanel buttonPanel = new JPanel(new GridLayout(5, 4, 5, 5));
        buttonPanel.add(memoryClear);
        buttonPanel.add(memoryRecall);
        buttonPanel.add(memoryMinus);
        buttonPanel.add(memoryPlus);
        buttonPanel.add(percent);
        buttonPanel.add(squareRoot);
        buttonPanel.add(reciprocal);
        buttonPanel.add(divide);
        buttonPanel.add(7);
        buttonPanel.add(8);
        buttonPanel.add(9);
        buttonPanel.add(multiply);
        buttonPanel.add(4);
        buttonPanel.add(5);
        buttonPanel.add(6);
        buttonPanel.add(subtract);
        buttonPanel.add(1);
        buttonPanel.add(2);
        buttonPanel.add(3);
        buttonPanel.add(add);
        buttonPanel.add(plusMinus);
        buttonPanel.add(0);
        buttonPanel.add(".");
        buttonPanel.add(equals);
        buttonPanel.add(clearEntry);
        buttonPanel.add(clearAll);
        buttonPanel.add(backspace);

        JPanel displayPanel = new JPanel(new BorderLayout());
        displayPanel.add(display, BorderLayout.CENTER);

        add(displayPanel, BorderLayout.NORTH);
        add(buttonPanel, BorderLayout.CENTER);

        setSize(300, 300);
        setLocationRelativeTo(null);
        setResizable(false);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
    }

    private void handleNumberInput(int number) {
        if (startNewNumber) {
            display.setText(String.valueOf(number));
            currentNumber = number;
            startNewNumber = false;
        } else {
            String current = display.getText();
            if (current.equals("0")) {
                display.setText(String.valueOf(number));
            } else {
                display.setText(current + number);
            }
            currentNumber = Double.parseDouble(display.getText());
        }
    }

    private void handleOperatorInput(char operator) {
        if (startNewNumber) {
            lastOperator = operator;
        } else {
            switch (lastOperator) {
                case '+':
                    result += currentNumber;
                    break;
                case '-':
                    result -= currentNumber;
                    break;
                case '*':
                    result *= currentNumber;
                    break;
                case '/':
                    result /= currentNumber;
                    break;
                case '%':
                    result %= currentNumber;
                    break;
                default:
                    result = currentNumber;
                    break;
            }
            display.setText(String.valueOf(result));
            currentNumber = result;
            startNewNumber = true;
            lastOperator = operator;
        }
    }

    public void actionPerformed(ActionEvent e) {
        Object source = e.getSource();
        if (source == backspace) {
            String current = display.getText();
            if (current.length() > 1) {
                display.setText(current.substring(0, current.length() - 1));
                currentNumber = Double.parseDouble(display.getText());
            } else {
                display.setText("0");
                currentNumber = 0;
                startNewNumber = true;
            }
        } else if (source == plusMinus) {
            currentNumber = -currentNumber;
            display.setText(String.valueOf(currentNumber));
        } else if (source == reciprocal) {
            currentNumber = 1 / currentNumber;
            display.setText(String.valueOf(currentNumber));
        } else if (source == squareRoot) {
            currentNumber = Math.sqrt(currentNumber);
            display.setText(String.valueOf(currentNumber));
        } else if (source == percent) {
            handleOperatorInput('%');
        } else if (source == clearEntry) {
            display.setText("0");
            currentNumber = 0;
            startNewNumber = true;
        } else if (source == clearAll) {
            result = 0;
            lastOperator = ' ';
            display.setText("0");
            currentNumber = 0;
            startNewNumber = true;
        } else if (source == memoryPlus) {
            memory += currentNumber;
        } else if (source == memoryMinus) {
            memory -= currentNumber;
        } else if (source == memoryRecall) {
            currentNumber = memory;
            display.setText(String.valueOf(currentNumber));
        } else if (source == memoryClear) {
            memory = 0;
        } else if (source == divide) {
            handleOperatorInput('/');
        } else if (source == multiply) {
            handleOperatorInput('*');
        } else if (source == subtract) {
            handleOperatorInput('-');
        } else if (source == add) {
            handleOperatorInput('+');
        } else if (source == equals) {
            switch (lastOperator) {
                case '+':
                    result += currentNumber;
                    break;
                case '-':
                    result -= currentNumber;
                    break;
                case '*':
                    result *= currentNumber;
                    break;
                case '/':
                    result /= currentNumber;
                    break;
                case '%':
                    result %= currentNumber;
                    break;
                default:
                    result = currentNumber;
                    break;
            }
            display.setText(String.valueOf(result));
            currentNumber = result;
            startNewNumber = true;
            lastOperator = ' ';
        } else {
            handleNumberInput((Integer) source);
        }
    }

    public static void main(String[] args) {
        Calculator calculator = new Calculator();
        calculator.setVisible(true);
    }

}

这个实现使用了Java的Swing GUI库来创建一个带有按钮和文本框的窗口，并在按钮上添加了相应的事件处理程序来实现计算器的功能。