Calendar处理

:arrow: /*
* 得到某年某周的第一天
*/
public static Date getFirstDayOfweek(int year, int week) {
Calendar calendar = new GregorianCalendar();
calendar.set(Calendar.YEAR, year);
calendar.set(Calendar.MONTH, Calendar.JANUARY);
calendar.set(Calendar.DATE, 1);
Calendar cal = (GregorianCalendar) calendar.clone();
cal.set(Calendar.DATE, week * 7);
return getFirstDayOfWeek(cal.getTime());
}

/*
* 取得当前日期所在周的第一天
*/
public static Date getFirstDayOfWeek(Date date) {
Calendar calendar = new GregorianCalendar();
calendar.setFirstDayOfWeek(Calendar.MONDAY);
calendar.set(Calendar.DATE, 1);
calendar.setTime(date);
calendar.set(Calendar.DAY_OF_WEEK, calendar.getFirstDayOfWeek() + 7);
return calendar.getTime();
}

/*
* 得到某年某周的最后一天
*/
public static Date getLastDayofweek(int year, int week) {
Calendar calendar = new GregorianCalendar();
calendar.set(Calendar.YEAR, year);
calendar.set(Calendar.MONTH, Calendar.JANUARY);
calendar.set(Calendar.DATE, 1);
Calendar cal = (GregorianCalendar) calendar.clone();
cal.add(Calendar.DATE, week * 7);
return getLastDayOfWeek(cal.getTime());
}

/*
* 取得当前日期所在周的最后一天
*/
public static Date getLastDayOfWeek(Date date) {
Calendar calendar = new GregorianCalendar();
calendar.setFirstDayOfWeek(Calendar.MONDAY);
calendar.setTime(date);
calendar.set(Calendar.DAY_OF_WEEK, calendar.getFirstDayOfWeek() + 6);
return calendar.getTime();
}

public static int getNowWeek(Date date) {
Calendar calendar = new GregorianCalendar();
calendar.setFirstDayOfWeek(Calendar.MONDAY);
calendar.setTime(date);
return Calendar.DAY_OF_WEEK;
}

/*
* 取得当前日期是多少周
*/
public static int getWeekOfYear(Date date) {
Calendar calendar = new GregorianCalendar();
calendar.setFirstDayOfWeek(Calendar.MONDAY);
calendar.setMinimalDaysInFirstWeek(7);
calendar.setTime(null != date ? date : new Date());
return calendar.get(Calendar.WEEK_OF_YEAR);
}

/*
* 取得当前日期是多少周
*
*/
public static int getyearweek(Date date) {
Calendar calendar = new GregorianCalendar();
calendar.setFirstDayOfWeek(Calendar.MONDAY);
calendar.setMinimalDaysInFirstWeek(7);
calendar.setTime(null != date ? date : new Date());
return calendar.get(Calendar.YEAR);
}

/*
* 字符转日前
*/
public static Date formatStrToDate(String str) {
SimpleDateFormat spd = new SimpleDateFormat("yyyy-MM-dd");
try {
Date date = spd.parse(str);
return date;
} catch (ParseException e) {
e.printStackTrace();
}
return null;
}

/*
* 格式化日前 yyyy-MM-dd
*/
public static String formatDateToStr(Date date) {
SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
return format.format(null != date ? date : new Date());
}