java 如何找到一个月中的第几周
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How to find week of the month
提问by user1686408
I like to know which week of the month a particular day falls. For example 20-Sep-2012 falls on 4th week of September but the below code displays it as 3 which is not correct. The system is dividing the days by 7 and returning the output and which is not I require. I have searched in Joda API's but not able to find the solution. Please let me know is there any way to figure out the week of a month, a day falls
我想知道某个特定日期是一个月的哪一周。例如 20-Sep-2012 落在 9 月的第 4 周，但下面的代码将其显示为 3，这是不正确的。系统将天数除以 7 并返回输出，这不是我需要的。我在 Joda API 中搜索过，但找不到解决方案。请让我知道有什么方法可以算出一个月中的一周，一天下降
Calendar ca1 = Calendar.getInstance();
ca1.set(2012,9,20);
int wk=ca1.get(Calendar.WEEK_OF_MONTH);
System.out.println("Week of Month :"+wk);
回答by Keppil
This is due to two reasons:
这是由于两个原因：
The first one is this (from the API):
第一个是这个（来自API）：
The first week of a month or year is defined as the earliest seven day period beginning on getFirstDayOfWeek() and containing at least getMinimalDaysInFirstWeek() days
一个月或一年的第一周定义为从 getFirstDayOfWeek() 开始并至少包含 getMinimalDaysInFirstWeek() 天的最早 7 天时间段
The default value for this varies (mine was 4), but you can set this to your preferred value with
这个默认值会有所不同（我的是 4），但您可以将其设置为您的首选值
Calendar.setMinimalDaysInFirstWeek()
Calendar.setMinimalDaysInFirstWeek()
The second reason is the one @Timmy brought up in his answer. You need to perform both changes for your code to work. Complete working example:
第二个原因是@Timmy 在他的回答中提到的。您需要执行这两项更改才能使代码正常工作。完整的工作示例：
public static void main(String[] args) {
Calendar ca1 = Calendar.getInstance();
ca1.set(2012, Calendar.SEPTEMBER, 20);
ca1.setMinimalDaysInFirstWeek(1);
int wk = ca1.get(Calendar.WEEK_OF_MONTH);
System.out.println("Week of Month :" + wk);
}
This prints
这打印
Week of Month :4
回答by Timmy
Month is zero-based. So ca1.set(2012,9,20) is actually setting the calendar to October.
月份是从零开始的。所以 ca1.set(2012,9,20) 实际上是将日历设置为十月。
回答by AnarchoEnte
To get sure the right month is set try using the month-constants provided by the Calendar-Class.
要确保设置了正确的月份，请尝试使用 Calendar-Class 提供的月份常量。
回答by Jason K.
For those working with Joda time, this is what I am using:
对于那些使用 Joda 时间的人，这就是我正在使用的：
/**
* For a week starting from Sunday, get the week of the month assuming a
* valid week is any week containing at least one day.
*
* 0=Last,1=First,2=Second...5=Fifth
*/
private int getWeekOfMonth( MutableDateTime calendar )
{
long time = calendar.getMillis();
int dayOfMonth = calendar.getDayOfMonth();
int firstWeekday;
int lastDateOfMonth;
int week;
int weeksInMonth;
calendar.setDayOfMonth( 1 );
firstWeekday = calendar.getDayOfWeek();
if (firstWeekday == 7)
{
firstWeekday = 0;
}
calendar.setHourOfDay( 0 );
calendar.addMonths( 1 );
calendar.addDays( -1 );
lastDateOfMonth = calendar.getDayOfMonth();
weeksInMonth = (int)Math.ceil( 1.0*(lastDateOfMonth + firstWeekday)/7 );
week = (byte)(1 + (dayOfMonth + firstWeekday - 1)/7);
week = (week == weeksInMonth)?0:week;
calendar.setMillis( time );
return week;
}
回答by kondra p
class test {
public static void main(String[] args){
Calendar cal = Calendar.getInstance();
cal.set(2016, Calendar.AUGUST, 01);
printDayOFWeek(cal, Calendar.MONDAY, 5);//prints monday on 5th week
}
}
private static void printDayOFWeek(Calendar cal, int day, int whatweek) {
cal.set(Calendar.DAY_OF_WEEK, day);//day = Mon, tue, wed,..etc
cal.set(Calendar.DAY_OF_WEEK_IN_MONTH, -1); //-1 return last week
Date last = cal.getTime();
cal.set(Calendar.DAY_OF_WEEK_IN_MONTH, whatweek);
Date one = cal.getTime();
if(one.before(last) || one.compareTo(last) ==0)
{
System.out.println(whatweek +"WEEK" + cal.getTime());
}
}
