今天是2014-04-06（星期日）。
我使用以下代码得到的输出是：
Start Date = 2014-04-07
End Date = 2014-04-13
这是我想要的输出：
Start Date = 2014-03-31
End Date = 2014-04-06
我怎样才能做到这一点？
这是我到目前为止完成的代码：
// Get calendar set to current date and time
Calendar c = GregorianCalendar.getInstance();
System.out.println("Current week = " + Calendar.DAY_OF_WEEK);
// Set the calendar to monday of the current week
c.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);
System.out.println("Current week = " + Calendar.DAY_OF_WEEK);
// Print dates of the current week starting on Monday
DateFormat df = new SimpleDateFormat("yyyy-MM-dd", Locale.getDefault());
String startDate = "", endDate = "";
startDate = df.format(c.getTime());
c.add(Calendar.DATE, 6);
endDate = df.format(c.getTime());
System.out.println("Start Date = " + startDate);
System.out.println("End Date = " + endDate);
答案 0 :(得分：21)
使用 Java 8 并保持与之前相同的原则（一周的第一天取决于您的Locale），您应该考虑使用以下内容：
DayOfWeek Locale
final DayOfWeek firstDayOfWeek = WeekFields.of(locale).getFirstDayOfWeek();
final DayOfWeek lastDayOfWeek = DayOfWeek.of(((firstDayOfWeek.getValue() + 5) % DayOfWeek.values().length) + 1);
LocalDate.now(/* tz */).with(TemporalAdjusters.previousOrSame(firstDayOfWeek)); // first day
LocalDate.now(/* tz */).with(TemporalAdjusters.nextOrSame(lastDayOfWeek)); // last day
考虑以下class：
private static class ThisLocalizedWeek {
// Try and always specify the time zone you're working with
private final static ZoneId TZ = ZoneId.of("Pacific/Auckland");
private final Locale locale;
private final DayOfWeek firstDayOfWeek;
private final DayOfWeek lastDayOfWeek;
public ThisLocalizedWeek(final Locale locale) {
this.locale = locale;
this.firstDayOfWeek = WeekFields.of(locale).getFirstDayOfWeek();
this.lastDayOfWeek = DayOfWeek.of(((this.firstDayOfWeek.getValue() + 5) % DayOfWeek.values().length) + 1);
}
public LocalDate getFirstDay() {
return LocalDate.now(TZ).with(TemporalAdjusters.previousOrSame(this.firstDayOfWeek));
}
public LocalDate getLastDay() {
return LocalDate.now(TZ).with(TemporalAdjusters.nextOrSame(this.lastDayOfWeek));
}
@Override
public String toString() {
return String.format( "The %s week starts on %s and ends on %s",
this.locale.getDisplayName(),
this.firstDayOfWeek,
this.lastDayOfWeek);
}
}
我们可以证明其用法如下：
final ThisLocalizedWeek usWeek = new ThisLocalizedWeek(Locale.US);
System.out.println(usWeek);
// The English (United States) week starts on SUNDAY and ends on SATURDAY
System.out.println(usWeek.getFirstDay()); // 2018-01-14
System.out.println(usWeek.getLastDay()); // 2018-01-20
final ThisLocalizedWeek frenchWeek = new ThisLocalizedWeek(Locale.FRANCE);
System.out.println(frenchWeek);
// The French (France) week starts on MONDAY and ends on SUNDAY
System.out.println(frenchWeek.getFirstDay()); // 2018-01-15
System.out.println(frenchWeek.getLastDay()); // 2018-01-21
只需使用：
c.setFirstDayOfWeek(Calendar.MONDAY);
现在，您的一周的第一天设置在Calendar.SUNDAY上。这个设置取决于您的Locale。
因此，更好替代方案是初始化Calendar，指定您感兴趣的Locale。
例如：
Calendar c = GregorianCalendar.getInstance(Locale.US);
...会为您提供当前输出，同时：
Calendar c = GregorianCalendar.getInstance(Locale.FRANCE);
...会为您提供预期的输出。
答案 1 :(得分：13)
好吧，看起来你得到了答案。这是一个加载项，在Java 8及更高版本中使用java.time。 （见Tutorial）
import java.time.DayOfWeek;
import java.time.LocalDate;
public class MondaySunday
{
public static void main(String[] args)
{
LocalDate today = LocalDate.now();
// Go backward to get Monday
LocalDate monday = today;
while (monday.getDayOfWeek() != DayOfWeek.MONDAY)
{
monday = monday.minusDays(1);
}
// Go forward to get Sunday
LocalDate sunday = today;
while (sunday.getDayOfWeek() != DayOfWeek.SUNDAY)
{
sunday = sunday.plusDays(1);
}
System.out.println("Today: " + today);
System.out.println("Monday of the Week: " + monday);
System.out.println("Sunday of the Week: " + sunday);
}
}
另一种方法，使用temporal adjusters。
import java.time.LocalDate;
import static java.time.DayOfWeek.MONDAY;
import static java.time.DayOfWeek.SUNDAY;
import static java.time.temporal.TemporalAdjusters.nextOrSame;
import static java.time.temporal.TemporalAdjusters.previousOrSame;
public class MondaySunday
{
public static void main(String[] args)
{
LocalDate today = LocalDate.now();
LocalDate monday = today.with(previousOrSame(MONDAY));
LocalDate sunday = today.with(nextOrSame(SUNDAY));
System.out.println("Today: " + today);
System.out.println("Monday of the Week: " + monday);
System.out.println("Sunday of the Week: " + sunday);
}
}
答案 2 :(得分：2)
这是我为获取本周的开始和结束日期所做的工作。
public static Date getWeekStartDate() {
Calendar calendar = Calendar.getInstance();
while (calendar.get(Calendar.DAY_OF_WEEK) != Calendar.MONDAY) {
calendar.add(Calendar.DATE, -1);
}
return calendar.getTime();
}
public static Date getWeekEndDate() {
Calendar calendar = Calendar.getInstance();
while (calendar.get(Calendar.DAY_OF_WEEK) != Calendar.MONDAY) {
calendar.add(Calendar.DATE, 1);
}
calendar.add(Calendar.DATE, -1);
return calendar.getTime();
}
答案 3 :(得分：0)
我使用以下方法检查给定日期是否属于当前周
public boolean isDateInCurrentWeek(Date date)
{
Date currentWeekStart, currentWeekEnd;
Calendar currentCalendar = Calendar.getInstance();
currentCalendar.setFirstDayOfWeek(Calendar.MONDAY);
while(currentCalendar.get(Calendar.DAY_OF_WEEK) != Calendar.MONDAY)
{
currentCalendar.add(Calendar.DATE,-1);//go one day before
}
currentWeekStart = currentCalendar.getTime();
currentCalendar.add(Calendar.DATE, 6); //add 6 days after Monday
currentWeekEnd = currentCalendar.getTime();
Calendar targetCalendar = Calendar.getInstance();
targetCalendar.setFirstDayOfWeek(Calendar.MONDAY);
targetCalendar.setTime(date);
Calendar tempCal = Calendar.getInstance();
tempCal.setTime(currentWeekStart);
boolean result = false;
while(!(tempCal.getTime().after(currentWeekEnd)))
{
if(tempCal.get(Calendar.DAY_OF_YEAR)==targetCalendar.get(Calendar.DAY_OF_YEAR))
{
result=true;
break;
}
tempCal.add(Calendar.DATE,1);//advance date by 1
}
return result;
}
答案 4 :(得分：0)
Calendar privCalendar = Calendar.getInstance();
Date fdow, ldow;
int dayofWeek = privCalendar.get ( Calendar.DAY_OF_WEEK );
Date fdow, ldow;
if( dayofWeek == Calendar.SUNDAY ) {
privCalendar.add ( Calendar.DATE, -1 * (dayofWeek -
Calendar.MONDAY ) - 7 );
fdow = privCalendar.getTime();
privCalendar.add( Calendar.DATE, 6 );
ldow = privCalendar.getTime();
} else {
privCalendar.add ( Calendar.DATE, -1 * (dayofWeek -
Calendar.MONDAY ) );
fdow = privCalendar.getTime();
privCalendar.add( Calendar.DATE, 6 );
ldow = privCalendar.getTime();
}
答案 5 :(得分：0)
/**
* Get the date of the first day in the week of the provided date
* @param date A date in the interested week
* @return The date of the first week day
*/
public static Date getWeekStartDate(Date date){
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.set(Calendar.DAY_OF_WEEK, getFirstWeekDay());
return cal.getTime();
}
/**
* Get the date of the last day in the week of the provided date
* @param date A date in the interested week
* @return The date of the last week day
*/
public static Date getWeekEndDate(Date date){
Calendar cal = Calendar.getInstance();
cal.setTime(date);
cal.add(Calendar.DATE, 6);// last day of week
return cal.getTime();
}
Date now = new Date(); // any date
Date weekStartDate = getWeekStartDate(now);
Date weekEndDate = getWeekEndDate(now);
// if you don't want the end date to be in the future
if(weekEndDate.after(now))
weekEndDate = now;
答案 6 :(得分：0)
使用 ThreeTen-Extra 库中方便的YearWeek类表示一整周。然后要求它确定该周中任一星期几的日期。
org.threeten.extra.YearWeek // Handy class representing a standard ISO 8601 week. Class found in the *ThreeTen-Extra* project, led by the same man as led JSR 310 and the *java.time* implementation.
.now( // Get the current week as seen in the wall-clock time used by the people of a certain region (a time zone).
ZoneId.of( "America/Chicago" )
) // Returns a `YearWeek` object.
.atDay( // Determine the date for a certain day within that week.
DayOfWeek.MONDAY // Use the `java.time.DayOfWeek` enum to specify which day-of-week.
) // Returns a `LocalDate` object.
LocalDate LocalDate类表示没有日期，没有time zone或offset-from-UTC的仅日期值。
时区对于确定日期至关重要。在任何给定时刻，日期都会在全球范围内变化。例如，Paris France午夜之后的几分钟是新的一天，而Montréal Québec仍然是“昨天”。
如果未指定时区，则JVM隐式应用其当前的默认时区。该默认值可能在运行时（！）期间change at any moment，因此您的结果可能会有所不同。最好将您的期望/期望时区明确指定为参数。如果紧急，请与您的用户确认区域。
以Continent/Region的格式指定proper time zone name，例如America/Montreal，Africa/Casablanca或Pacific/Auckland。切勿使用2-4个字母的缩写，例如EST或IST，因为它们不是真正的时区，不是标准化的，甚至不是唯一的（！）。
ZoneId z = ZoneId.of( "America/Montreal" ) ;
LocalDate today = LocalDate.now( z ) ;
如果要使用JVM的当前默认时区，请提出要求并作为参数传递。如果省略，代码将变得难以理解，因为我们不确定您是否打算使用默认值，还是像许多程序员一样不知道该问题。
ZoneId z = ZoneId.systemDefault() ; // Get JVM’s current default time zone.
或指定日期。您可以用数字设置月份，一月至十二月的理智编号为1-12。
LocalDate ld = LocalDate.of( 1986 , 2 , 23 ) ; // Years use sane direct numbering (1986 means year 1986). Months use sane numbering, 1-12 for January-December.
或者更好的是，使用预定义的Month枚举对象，每年的每个月使用一个。提示：在整个代码库中使用这些Month对象，而不是仅使用整数，可以使您的代码更具自记录性，确保有效值并提供type-safety。 Year和YearMonth的同上。
LocalDate ld = LocalDate.of( 2014 , Month.APRIL , 6 ) ;
YearWeek 您对从星期一到星期日的一周的定义与ISO 8601标准的定义匹配。
将ThreeTen-Extra库添加到您的项目中，以访问代表标准周的YearWeek类。
YearWeek week = YearWeek.from( ld ) ; // Determine the week of a certain date.
或者获得今天的星期。
YearWeek week = YearWeek.now( z ) ;
获取星期几的日期。通过使用DayOfWeek枚举来指定哪一天。
LocalDate firstOfWeek = week.atDay( DayOfWeek.MONDAY ) ;
LocalDate lastOfWeek = week.atDay( DayOfWeek.SUNDAY ) ;