用java代码设计一个日历记事本。 主要要求： (1)实现日期（阳历）的显示、查看，显示星期与日期的对应； (2)选中相应日期后，如果有历史记录，在文本框中显示记录的内容 (3)选中相应日期后，如果无历史记录，可以在文本框中记录内容并保存到txt文件中 (4)在保存文件时，提供一个以当前时间（年-月-日-时-分-秒）为名称的默认文件名。

以下是一个简单的基于Java Swing的日历记事本的实现代码。其中，使用了Java中的Calendar类来获取当前日期，使用了JFileChooser类来选择保存文件的路径。

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.FlowLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;

import javax.swing.JButton;
import javax.swing.JFileChooser;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;

public class CalendarNotebook extends JFrame implements ActionListener {

    private static final long serialVersionUID = 1L;

    private JButton[] dayButtons;
    private JLabel monthLabel;
    private JTextArea noteArea;
    private JButton saveButton;

    private int currentYear;
    private int currentMonth;
    private int currentDay;

    public CalendarNotebook() {
        super("Calendar Notebook");

        // 获取当前日期
        Calendar calendar = Calendar.getInstance();
        currentYear = calendar.get(Calendar.YEAR);
        currentMonth = calendar.get(Calendar.MONTH);
        currentDay = calendar.get(Calendar.DAY_OF_MONTH);

        // 创建顶部面板
        JPanel topPanel = new JPanel(new FlowLayout(FlowLayout.CENTER));
        JButton prevButton = new JButton("<");
        prevButton.addActionListener(this);
        topPanel.add(prevButton);
        monthLabel = new JLabel(getMonthString(currentMonth) + " " + currentYear);
        topPanel.add(monthLabel);
        JButton nextButton = new JButton(">");
        nextButton.addActionListener(this);
        topPanel.add(nextButton);

        // 创建中间面板
        JPanel middlePanel = new JPanel(new GridLayout(6, 7));
        dayButtons = new JButton[42];
        for (int i = 0; i < 42; i++) {
            dayButtons[i] = new JButton();
            dayButtons[i].setPreferredSize(new Dimension(50, 50));
            dayButtons[i].setEnabled(false);
            dayButtons[i].addActionListener(this);
            middlePanel.add(dayButtons[i]);
        }
        updateCalendar();

        // 创建底部面板
        JPanel bottomPanel = new JPanel(new BorderLayout());
        noteArea = new JTextArea();
        noteArea.setLineWrap(true);
        noteArea.setWrapStyleWord(true);
        JScrollPane scrollPane = new JScrollPane(noteArea);
        bottomPanel.add(scrollPane, BorderLayout.CENTER);
        saveButton = new JButton("Save");
        saveButton.addActionListener(this);
        bottomPanel.add(saveButton, BorderLayout.SOUTH);

        // 添加组件到窗口
        add(topPanel, BorderLayout.NORTH);
        add(middlePanel, BorderLayout.CENTER);
        add(bottomPanel, BorderLayout.SOUTH);

        // 设置窗口属性
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        setSize(600, 400);
        setLocationRelativeTo(null);
        setVisible(true);
    }

    // 更新日历
    private void updateCalendar() {
        // 获取当前月份的第一天
        Calendar calendar = Calendar.getInstance();
        calendar.set(currentYear, currentMonth, 1);
        int firstDay = calendar.get(Calendar.DAY_OF_WEEK) - 1;

        // 获取当前月份的天数
        int daysInMonth = calendar.getActualMaximum(Calendar.DAY_OF_MONTH);

        // 更新日历按钮的文本和可用状态
        for (int i = 0; i < 42; i++) {
            if (i >= firstDay && i < firstDay + daysInMonth) {
                dayButtons[i].setText(String.valueOf(i - firstDay + 1));
                dayButtons[i].setEnabled(true);
            } else {
                dayButtons[i].setText("");
                dayButtons[i].setEnabled(false);
            }
        }

        // 更新选中日期的背景色
        for (int i = 0; i < 42; i++) {
            if (dayButtons[i].isEnabled() && Integer.parseInt(dayButtons[i].getText()) == currentDay) {
                dayButtons[i].setBackground(Color.YELLOW);
            } else {
                dayButtons[i].setBackground(null);
            }
        }
    }

    // 获取月份的字符串表示
    private String getMonthString(int month) {
        switch (month) {
        case 0:
            return "January";
        case 1:
            return "February";
        case 2:
            return "March";
        case 3:
            return "April";
        case 4:
            return "May";
        case 5:
            return "June";
        case 6:
            return "July";
        case 7:
            return "August";
        case 8:
            return "September";
        case 9:
            return "October";
        case 10:
            return "November";
        case 11:
            return "December";
        default:
            return "";
        }
    }

    // 显示历史记录或新建记录
    private void showNote() {
        // 获取选中的日期
        int selectedDay = -1;
        for (int i = 0; i < 42; i++) {
            if (dayButtons[i].isEnabled() && dayButtons[i].getBackground() == Color.YELLOW) {
                selectedDay = Integer.parseInt(dayButtons[i].getText());
                break;
            }
        }

        // 显示历史记录或新建记录
        if (selectedDay == -1) {
            noteArea.setText("");
        } else {
            String filename = currentYear + "-" + (currentMonth + 1) + "-" + selectedDay + ".txt";
            File file = new File(filename);
            if (file.exists()) {
                try {
                    noteArea.setText("");
                    noteArea.read(new java.io.FileReader(file), null);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            } else {
                noteArea.setText("");
            }
        }
    }

    // 保存记录
    private void saveNote() {
        // 获取选中的日期和文本框内容
        int selectedDay = -1;
        String noteText = noteArea.getText();
        for (int i = 0; i < 42; i++) {
            if (dayButtons[i].isEnabled() && dayButtons[i].getBackground() == Color.YELLOW) {
                selectedDay = Integer.parseInt(dayButtons[i].getText());
                break;
            }
        }

        // 保存记录到文件
        if (selectedDay == -1) {
            JOptionPane.showMessageDialog(this, "Please select a date.");
        } else {
            String filename = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss").format(new Date()) + ".txt";
            JFileChooser fileChooser = new JFileChooser();
            fileChooser.setDialogTitle("Save Note");
            fileChooser.setSelectedFile(new File(filename));
            int result = fileChooser.showSaveDialog(this);
            if (result == JFileChooser.APPROVE_OPTION) {
                File file = fileChooser.getSelectedFile();
                try {
                    FileWriter writer = new FileWriter(file);
                    writer.write(noteText);
                    writer.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    @Override
    public void actionPerformed(ActionEvent e) {
        Object source = e.getSource();
        if (source instanceof JButton) {
            JButton button = (JButton) source;
            if (button.getText().equals("<")) {
                currentMonth--;
                if (currentMonth < 0) {
                    currentMonth = 11;
                    currentYear--;
                }
            } else if (button.getText().equals(">")) {
                currentMonth++;
                if (currentMonth > 11) {
                    currentMonth = 0;
                    currentYear++;
                }
            } else {
                currentDay = Integer.parseInt(button.getText());
            }
            monthLabel.setText(getMonthString(currentMonth) + " " + currentYear);
            updateCalendar();
            showNote();
        } else if (source == saveButton) {
            saveNote();
        }
    }

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

}