Java中用Calendar类计算周和周的起始日期(转)

package com.tongyue.hot.web;

import java.util.Calendar;

import java.util.Date;

import java.util.GregorianCalendar;

public class Dateutil {

/**

* 取得当前日期是多少周

*

* @param date

* @return

*/

public static int getWeekOfYear(Date date) {

Calendar c = new GregorianCalendar();

c.setFirstDayOfWeek(Calendar.MONDAY);

c.setMinimalDaysInFirstWeek(7);

c.setTime (date);

return c.get(Calendar.WEEK_OF_YEAR);

}

/**

* 得到某一年周的总数

*

* @param year

* @return

*/

public static int getMaxWeekNumOfYear(int year) {

Calendar c = new GregorianCalendar();

c.set(year, Calendar.DECEMBER, 31, 23, 59, 59);

return getWeekOfYear(c.getTime());

}

/**

* 得到某年某周的第一天

*

* @param year

* @param week

* @return

*/

public static Date getFirstDayOfWeek(int year, int week) {

Calendar c = new GregorianCalendar();

c.set(Calendar.YEAR, year);

c.set (Calendar.MONTH, Calendar.JANUARY);

c.set(Calendar.DATE, 1);

Calendar cal = (GregorianCalendar) c.clone();

cal.add(Calendar.DATE, week * 7);

return getFirstDayOfWeek(cal.getTime ());

}

/**

* 得到某年某周的最后一天

*

* @param year

* @param week

* @return

*/

public static Date getLastDayOfWeek(int year, int week) {

Calendar c = new GregorianCalendar();

c.set(Calendar.YEAR, year);

c.set(Calendar.MONTH, Calendar.JANUARY);

c.set(Calendar.DATE, 1);

Calendar cal = (GregorianCalendar) c.clone();

cal.add(Calendar.DATE , week * 7);

return getLastDayOfWeek(cal.getTime());

}

/**

* 取得指定日期所在周的第一天

*

* @param date

* @return

*/

public static Date getFirstDayOfWeek(Date date) {

Calendar c = new GregorianCalendar();

c.setFirstDayOfWeek(Calendar.MONDAY);

c.setTime(date);

c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek()); // Monday

return c.getTime ();

}

/**

* 取得指定日期所在周的最后一天

*

* @param date

* @return

*/

public static Date getLastDayOfWeek(Date date) {

Calendar c = new GregorianCalendar();

c.setFirstDayOfWeek(Calendar.MONDAY);

c.setTime(date);

c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek() + 6); // Sunday

return c.getTime();

}

/**

* 取得当前日期所在周的第一天

*

* @param date

* @return

*/

public static Date getFirstDayOfWeek() {

Calendar c = new GregorianCalendar();

c.setFirstDayOfWeek(Calendar.MONDAY);

c.setTime(new Date());

c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek()); // Monday

return c.getTime ();

}

/**

* 取得当前日期所在周的最后一天

*

* @param date

* @return

*/

public static Date getLastDayOfWeek() {

Calendar c = new GregorianCalendar();

c.setFirstDayOfWeek(Calendar.MONDAY);

c.setTime(new Date());

c.set(Calendar.DAY_OF_WEEK, c.getFirstDayOfWeek() + 6); // Sunday

return c.getTime();

}

/*

*

public static void main(String[] args) {

int year = 2009;

int week = 1;

// 以2006-01-02位例

Calendar c = new GregorianCalendar();

c.set(2009, Calendar.DECEMBER, 7);

Date d = c.getTime();

System.out.println("current date = " + d);

System.out.println("getWeekOfYear = " + getWeekOfYear(d));

System.out.println("getMaxWeekNumOfYear = " + getMaxWeekNumOfYear(year));

System.out.println("getFirstDayOfWeek = " + getFirstDayOfWeek(year, week));

System.out.println("getLastDayOfWeek = " + getLastDayOfWeek(year, week));

System.out.println ("getFirstDayOfWeek = " + getFirstDayOfWeek(d));

System.out.println("getLastDayOfWeek = " + getLastDayOfWeek(d));

System.out.println ("getFirstDayOfWeek = " + getFirstDayOfWeek());

System.out.println("getLastDayOfWeek = " + getLastDayOfWeek());

}

*/

}