Java – 如何计算每周的第一天和最后一天
我正在尝试创建一个如下所示的每周日历： http ： //dhtmlx.com/docs/products/dhtmlxScheduler/sample_basic.html
我怎样才能计算每周的日期？ 例如，本周是：
星期一星期天
6月7日，6月8日，6月9日，6月10日，6月11日，6月12日，6月13日
我想这可以做你想要的：
// Get calendar set to current date and time Calendar c = Calendar.getInstance(); // Set the calendar to monday of the current week c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY); // Print dates of the current week starting on Monday DateFormat df = new SimpleDateFormat("EEE dd/MM/yyyy"); for (int i = 0; i < 7; i++) { System.out.println(df.format(c.getTime())); c.add(Calendar.DATE, 1); } 本周的第一天。
Calendar c = Calendar.getInstance(); while (c.get(Calendar.DAY_OF_WEEK) != Calendar.MONDAY) { c.add(Calendar.DATE, -1); }
简单地设置星期几似乎不可靠。 请考虑以下简单代码：
Calendar calendar = Calendar.getInstance(Locale.GERMANY); calendar.set(2011, Calendar.SEPTEMBER, 18); System.out.printf("Starting day: %tF%n", calendar); calendar.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY); System.out.printf("Last monday: %tF%n", calendar); System.out.printf("First day of week: %d%n", calendar.getFirstDayOfWeek());
运行此程序的结果是：
Starting day: 2011-09-18 Last monday: 2011-09-19 First day of week: 2
换句话说，它及时向前迈进了一步。 对于德语区域设置，这实际上不是预期的答案。 请注意，日历正确地使用星期一作为一周的第一天（可能仅用于计算一年中的一周）。
使用Java 8中的新日期和时间API，您可以：
LocalDate now = LocalDate.now(); // determine country (Locale) specific first day of current week DayOfWeek firstDayOfWeek = WeekFields.of(Locale.getDefault()).getFirstDayOfWeek(); LocalDate startOfCurrentWeek = now.with(TemporalAdjusters.previousOrSame(firstDayOfWeek)); // determine last day of current week DayOfWeek lastDayOfWeek = firstDayOfWeek.plus(6); // or minus(1) LocalDate endOfWeek = now.with(TemporalAdjusters.nextOrSame(lastDayOfWeek)); // Print the dates of the current week LocalDate printDate = startOfCurrentWeek; DateTimeFormatter formatter = DateTimeFormatter.ofPattern("EEE dd/MM/yyyy"); for (int i=0; i < 7; i++) { System.out.println(printDate.format(formatter)); printDate = printDate.plusDays(1); }
Java.time
使用Java 8中内置的java.time库：
import java.time.DayOfWeek; import java.time.LocalDate; import static java.time.temporal.TemporalAdjusters.previousOrSame; import static java.time.temporal.TemporalAdjusters.nextOrSame; LocalDate now = LocalDate.now(); # 2015-11-23 LocalDate first = now.with(previousOrSame(DayOfWeek.MONDAY)); # 2015-11-23 LocalDate last = now.with(nextOrSame(DayOfWeek.SUNDAY)); # 2015-11-29
您可以迭代DayOfWeek.values()以获取当前所有工作日
DayOfWeek.values(); # Array(MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY, SUNDAY) for (DayOfWeek day: DayOfWeek.values()) { System.out.print(first.with(nextOrSame(day))); } # 2015-11-23, 2015-11-24, 2015-11-25, 2015-11-26, 2015-11-27, 2015-11-28, 2015-11-29
您可以在此基础上进行构建：以下代码打印了从现在起15周内每周的第一个和最后一个日期。
Calendar c = Calendar.getInstance(); c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY); for(int i=0; i<15; i++) { System.out.print("Start Date : " + c.getTime() + ", "); c.add(Calendar.DAY_OF_WEEK, 6); System.out.println("End Date : " + c.getTime()); c.add(Calendar.DAY_OF_WEEK, 1); }
如果您知道（星期五）的哪一天和当前日期（6月11日），您可以计算本周的其他天数。
我建议你使用Joda Time库。 Gregorian Calendar类有weekOfWeekyear和dayOfWeek方法。
Calendar startCal = Calendar.getInstance(); startCal.setTimeInMillis(startDate); Calendar endCal = Calendar.getInstance(); endCal.setTimeInMillis(endDate); SimpleDateFormat sdf = new SimpleDateFormat("dd-MMMM-yyyy"); while (startCal.before(endCal)) { int weekNumber = startCal.get(Calendar.WEEK_OF_YEAR); Calendar cal = Calendar.getInstance(); cal.set(Calendar.DAY_OF_WEEK, Calendar.SUNDAY); cal.set(Calendar.WEEK_OF_YEAR, weekNumber); Date sunday = cal.getTime(); Log.d("sunday", "" + sdf.format(sunday)); cal.set(Calendar.DAY_OF_WEEK, Calendar.SATURDAY); cal.set(Calendar.WEEK_OF_YEAR, weekNumber); Date saturday = cal.getTime(); Log.d("saturday", "" + sdf.format(saturday)); weekNumber = weekNumber + 1; startCal.set(Calendar.WEEK_OF_YEAR, weekNumber); }
是。 使用Joda时间
您正在寻找的算法（计算任何给定日期的星期几）是“Zeller’s Congruence”。 这是一个Java实现：
http://technojeeves.com/joomla/index.php/free/57-zellers-congruence