Calendar GregorianCalendar

      GregorianCalendar is a concrete subclass of Calendar and provides the standard calendar system used by most of the world.

      public abstract class Calendar 说明calendar类是一个抽象类，从javadoc中可看出来，GregorianCalendar应该是Calendar类的唯一实现类了。

      Date类中，多数的方法都已经成为Deprecated，所以，我们在使用的时候，可以用Calendar类来设置好我们需要的时间之后，用Calendar类的gettime方法来取得这个Date对象。

import java.util.Calendar;import java.util.Date;import java.util.GregorianCalendar;public class WeekUtil {/** * 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();p(c.getTime());cal.add(Calendar.DATE, week * 7);return getFirstDayOfWeek(cal.getTime());}public static void p(Object o) {System.out.println(o);}/** * 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());}/** * 取得当前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()); // Mondayreturn c.getTime();}/** * 取得当前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); // Sundayreturn c.getTime();}}