java 获取周、月、年的第一天以及最后一天的详细代码

public class MyCalendar {

public static Date getDate(Calendar c) {

return new Date(c.getTimeInMillis());

}

/**

* 得到本周第一天

* @return

*/

public static Calendar getFirstDayOfWeek() {

Calendar monday = Calendar.getInstance();

return getADayOfWeek(monday, Calendar.MONDAY);

}

/**

* 得到本周第一天

* @param day

* @return

*/

public static Calendar getFirstDayOfWeek(Calendar day) {

Calendar monday = (Calendar) day.clone();

return getADayOfWeek(monday, Calendar.MONDAY);

}

/**

* 得到本周最后一天

* @return

*/

public static Calendar getLastDayOfWeek() {

Calendar sunday = Calendar.getInstance();

return getADayOfWeek(sunday, Calendar.SUNDAY);

}

/**

* 得到本周最后一天

* @param day

* @return

*/

public static Calendar getLastDayOfWeek(Calendar day) {

Calendar sunday = (Calendar) day.clone();

return getADayOfWeek(sunday, Calendar.SUNDAY);

}

private static Calendar getADayOfWeek(Calendar day, int dayOfWeek) {

int week = day.get(Calendar.DAY_OF_WEEK);

if (week == dayOfWeek)

return day;

int diffDay = dayOfWeek - week;

if (week == Calendar.SUNDAY) {

diffDay -= 7;

} else if (dayOfWeek == Calendar.SUNDAY) {

diffDay += 7;

}

day.add(Calendar.DATE, diffDay);

return day;

}

/**

* 得到本月的第一天

* @return

*/

public static Calendar getMonthFirstDay() {

Calendar calendar = Calendar.getInstance();

calendar.set(Calendar.DAY_OF_MONTH, calendar

.getActualMinimum(Calendar.DAY_OF_MONTH));

return calendar;

}

/**

* 得到本月的最后一天

*

* @return

*/

public static Calendar getMonthLastDay() {

Calendar calendar = Calendar.getInstance();

calendar.set(Calendar.DAY_OF_MONTH, calendar

.getActualMaximum(Calendar.DAY_OF_MONTH));

return calendar;

}

/**

* 得到本年度第一天

* @return

*/

public static Calendar getYearFristDay(){

Calendar calendar =Calendar.getInstance();

int year=calendar.get(Calendar.YEAR);

calendar.clear();

calendar.set(Calendar.YEAR, year);

return calendar;

}

/**

* 得到本年度最后一天

* @return

*/

public static Calendar getYearLastDay(){

Calendar calendar =Calendar.getInstance();

int year=calendar.get(Calendar.YEAR);

calendar.clear();

calendar.set(Calendar.YEAR, year);

calendar.roll(Calendar.DAY_OF_YEAR, -1);

return calendar;

}

public static void main(String[] args){

Calendar day=Calendar.getInstance();

int month=day.get(Calendar.DAY_OF_MONTH);

System.out.println("month:"+month);

SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd 00:00:00");

String dates=format.format(MyCalendar.getDate(MyCalendar.getFirstDayOfWeek()));

String datee=format.format(MyCalendar.getDate(MyCalendar.getLastDayOfWeek()));

String months=format.format(MyCalendar.getDate(MyCalendar.getMonthFirstDay()));

String monthe=format.format(MyCalendar.getDate(MyCalendar.getMonthLastDay()));

String years=format.format(MyCalendar.getDate(MyCalendar.getYearFristDay()));

String yeare=format.format(MyCalendar.getDate(MyCalendar.getYearLastDay()));

System.out.println("weekday :"+dates+"=========== end:"+datee);

System.out.println("months :"+months+"=========== end:"+monthe);

System.out.println("years :"+years+"=========== end:"+yeare);

}

}