JAVA实现日历中遇到的一些问题

Question

class Calendar implements ItemListener{
	private static final int s_year = 1970;
	private static final int e_year = 2050;
	private final JComboBox cboYear;
	private final JComboBox cboMonth;
	private final JComboBox cboDay;
	public Calendar(JComboBox cboYear, JComboBox cboMonth, JComboBox cboDay) {
		this.cboYear = cboYear;
		this.cboMonth = cboMonth;
		this.cboDay = cboDay;
	}
	/**
	 * 初始化年月日下来列表框
	 */
	public void AddInfo() {
		//年下拉选择框
		for (int i = s_year; i < e_year; i++) {
			cboYear.addItem("" + i);
		}
		//月下拉选择框
		for (int i = 0; i < 12; i++) {
			cboMonth.addItem("" + (i + 1));
		}
		//日下拉选择框
		for (int j = 0; j < 31; j++) {
			cboDay.addItem("" + (j + 1));
		}
	}
	@Override
	public void itemStateChanged(ItemEvent e) {
		Object obj = cboMonth.getSelectedItem();// 取得选中月份
		if (obj != null) {
			cboDay.removeAllItems();// 清空日的下拉列表框
			int month = Integer.parseInt(obj.toString());
			int days = 31;
			if (month == 4 || month == 6 || month == 9 || month == 11) {
				days = 30;
			}
			else if (month == 2) {
				//取得选中年份
				int year = Integer.parseInt(Objects.requireNonNull(cboYear.getSelectedItem()).toString());
				if (year % 400 == 0 || (year % 4 == 0 && year % 100 != 0)) {// 是闰年
					days = 29;
				}
				else {// 不是闰年
					days = 28;
				}
			}
			for (int j = 0; j < days; j++) {
				cboDay.addItem("" + (j + 1));
			}
		}
	}
}

这是日历类。

		cb_year.setSize(100, 50);
		cb_month.setSize(100, 50);
		cb_day.setSize(100, 50);
		cb_year.addItem(null);
		cb_month.addItem(null);
		cb_day.addItem(null);
		calendar.AddInfo();
		container.add(cb_year);
		container.add(cb_month);
		container.add(cb_day);

我在主界面中只会这样实现，我不知道如何调用类中的ItemListener函数来让日期中的日随月份的变化而变化，求解答！

Answer 1

要定义相应的触发事件，来控制月变化时，对应的日也随之变化