怎么用Java写一个带有窗体的日历

要用Java写一个带有窗体的日历，可以使用Java的Swing库来创建窗体和组件。

下面是一个简单的示例代码，展示了如何使用Java编写一个带有窗体的日历：

import javax.swing.*; import java.awt.*; import java.awt.event.ActionEvent; import java.awt.event.ActionListener; import java.time.LocalDate; import java.time.YearMonth;  public class CalendarApp extends JFrame {     private YearMonth currentYearMonth;     private JLabel monthLabel;     private JButton prevButton;     private JButton nextButton;     private JTable calendarTable;      public CalendarApp() {         currentYearMonth = YearMonth.now();          setTitle("Calendar App");         setSize(400, 300);         setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);         setLocationRelativeTo(null);          monthLabel = new JLabel("", JLabel.CENTER);         calendarTable = new JTable(6, 7);          prevButton = new JButton("Prev");         prevButton.addActionListener(new ActionListener() {             @Override             public void actionPerformed(ActionEvent e) {                 currentYearMonth = currentYearMonth.minusMonths(1);                 updateCalendar();             }         });          nextButton = new JButton("Next");         nextButton.addActionListener(new ActionListener() {             @Override             public void actionPerformed(ActionEvent e) {                 currentYearMonth = currentYearMonth.plusMonths(1);                 updateCalendar();             }         });          updateCalendar();          setLayout(new BorderLayout());         add(monthLabel, BorderLayout.NORTH);         add(new JScrollPane(calendarTable), BorderLayout.CENTER);          JPanel buttonPanel = new JPanel();         buttonPanel.add(prevButton);         buttonPanel.add(nextButton);         add(buttonPanel, BorderLayout.SOUTH);     }      private void updateCalendar() {         monthLabel.setText(currentYearMonth.getYear() + "年" + currentYearMonth.getMonthValue() + "月");          LocalDate firstDayOfMonth = currentYearMonth.atDay(1);         int firstDayOfWeek = firstDayOfMonth.getDayOfWeek().getValue();          int daysInMonth = currentYearMonth.lengthOfMonth();         int numRows = (int) Math.ceil((firstDayOfWeek + daysInMonth) / 7.0);          String[] columnNames = {"周日", "周一", "周二", "周三", "周四", "周五", "周六"};         Object[][] data = new Object[numRows][7];          int day = 1 - firstDayOfWeek;         for (int i = 0; i < numRows; i++) {             for (int j = 0; j < 7; j++) {                 if (day > 0 && day <= daysInMonth) {                     data[i][j] = day;                 } else {                     data[i][j] = "";                 }                 day++;             }         }          calendarTable.setModel(new javax.swing.table.DefaultTableModel(data, columnNames));         calendarTable.setDefaultRenderer(calendarTable.getColumnClass(0), new CalendarCellRenderer());     }      private class CalendarCellRenderer extends DefaultTableCellRenderer {         @Override         public Component getTableCellRendererComponent(JTable table, Object value, boolean isSelected, boolean hasFocus, int row, int column) {             JLabel label = (JLabel) super.getTableCellRendererComponent(table, value, isSelected, hasFocus, row, column);             if (value != null) {                 int day = (int) value;                 if (day == LocalDate.now().getDayOfMonth() && currentYearMonth.equals(YearMonth.now())) {                     label.setForeground(Color.RED);                 } else {                     label.setForeground(table.getForeground());                 }             }             return label;         }     }      public static void main(String[] args) {         SwingUtilities.invokeLater(new Runnable() {             @Override             public void run() {                 new CalendarApp().setVisible(true);             }         });     } } 

这个示例代码创建了一个带有窗体的日历应用，可以通过Prev和Next按钮切换月份。日历表格中，当前日期会以红色显示。

在这个示例代码中，我们使用了Swing的JFrame、JLabel、JButton、JTable等组件来构建窗体和日历表格。updateCalendar()方法用于更新日历表格的内容。CalendarCellRenderer类用于自定义单元格的渲染，以便高亮显示当前日期。

通过运行main()方法，可以启动日历应用并显示窗体。