Java获取当前年份、月份和日期是通过Calendar类的实例对象来获取的。
首先创建一个Calendar类的实例对象，Calendar类属于java.util包。
Calendar calendar = Calendar.getInstance();
获取当前年份、月份和日期等。
// 获取当前年int year = calendar.get(Calendar.YEAR); // 获取当前月int month = calendar.get(Calendar.MONTH) + 1; // 获取当前日int day = calenedar.get(Calendar.DATE); // 获取当前小时int hour = calendar.get(Calendar.HOUR_OF_DAY); // 获取当前分钟int minute = calendar.get(Calendar.MINUTE); // 获取当前秒int second = calendar.get(Calendar.SECOND); // 获取当前是本周第几天int dayOfWeek = calendar.get(Calendar.DAY_OF_WEEK); // 获取当前是本月第几天int dayOfMonth = calendar.get(Calendar.DAY_OF_MONTH); // 获取当前是本年第几天int dayOfYear = calendar.get(Calendar.DAY_OF_YEAR);
获取当月的第一天和最后一天的字符串。
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd"); // 获取当月第一天calendar = Calendar.getInstance();calendar.add(Calendar.MONTH, 0);calendar.set(Calendar.DAY_OF_MONTH, 1); String firstday = format.format(calendar.getTime()); // 获取当月最后一天calendar = Calendar.getInstance(); calendar.add(Calendar.MONTH, 1); calendar.set(Calendar.DAY_OF_MONTH, 0); String lastday = format.format(calendar.getTime()); // 打印结果字符串System.out.println("本月第一天和最后一天分别是：" + firstday + " 和 " + lastday + "。");
另外也可以使用Date类的实例对象配合SimpleDateFormat类的实例对象来获取当前日期字符串。
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss");Date date = new Date(); System.out.println("当前日期字符串：" + format.format(date) + "。");
获取上个星期第一天的某个小时的时间戳
public static Long getPreviousWeekday(int hour) {int week = -1;int mondayPlus = getMondayPlus();GregorianCalendar currentDate = new GregorianCalendar();currentDate.add(Calendar.DATE, mondayPlus + 7 * week);Date monday = currentDate.getTime();TimeZone curTimeZone = TimeZone.getTimeZone("GMT+8");Calendar c = Calendar.getInstance(curTimeZone);c.setTime(monday);c.set(Calendar.HOUR_OF_DAY, hour);c.set(Calendar.MINUTE, 0);c.set(Calendar.SECOND, 0);// Date z = c.getTime();// SimpleDateFormat sdf = new SimpleDateFormat(yyyy_MM_dd);// System.out.println(sdf.format(z));return c.getTime().getTime();}public static int getMondayPlus() {Calendar cd = Calendar.getInstance();int dayOfWeek = cd.get(Calendar.DAY_OF_WEEK) - 1;if (dayOfWeek == 1) {return 0;}return (1 - dayOfWeek);}
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