JAVA中用CALENDAR类计算周和周的起始日期

推荐安卓开发神器（里面有各种UI特效和android代码库实例）

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()); 
  }
 */ 
}