Java中对日期的常用处理（转）

import java.text.SimpleDateFormat;   
import java.util.Calendar;   
import java.util.Date;   
import java.util.GregorianCalendar;   
  
/** *//**  
 *   
 * @author zzk  
 *  
 */  
public class DateUtil {   
  
    /** *//**  
     * 取得某天相加(减)後的那一天  
     *   
     * @param date  
     * @param num(可正可负)  
     * @return  
     */  
    public static Date getAnotherDate(Date date, int num) {   
        Calendar c = Calendar.getInstance();   
        c.setTime(date);   
        c.add(Calendar.DAY_OF_YEAR, num);   
        return c.getTime();   
    }   
  
    /** *//**  
     * 取得某月的的最后一天  
     *   
     * @param year  
     * @param month  
     * @return  
     */  
    public static Date getLastDayOfMonth(int year, int month) {   
        Calendar cal = Calendar.getInstance();   
        cal.set(Calendar.YEAR, year);// 年   
        cal.set(Calendar.MONTH, month - 1);// 月，因为Calendar里的月是从0开始，所以要减1   
        //设置该月实际的最后一天   
        cal.set(Calendar.DATE,cal.getActualMaximum(Calendar.DATE));   
        return cal.getTime();// 获得月末是几号    
    }   
    
     /** *//**  
      * 取得某天是一年中的多少周  
     *   
     * @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);   
    }   
  
    /** *//**  
     * 取得某天所在周的第一天  
     *   
     * @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());   
        return c.getTime();   
    }   
  
    /** *//**  
     * 取得某天所在周的最后一天  
     *   
     * @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);   
        return c.getTime();   
    }   
  
    /** *//**  
     * 取得某一年共有多少周  
     *   
     * @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());   
    }   
       
    /** *//**  
     * 取得某年某周的第一天  
     * 对于交叉:2008-12-29到2009-01-04属于2008年的最后一周,2009-01-05为2009年第一周的第一天  
     * @param year  
     * @param week  
     * @return  
     */  
    public static Date getFirstDayOfWeek(int year, int week) {   
        Calendar calFirst = Calendar.getInstance();   
        calFirst.set(year, 0, 7);   
        Date firstDate = getFirstDayOfWeek(calFirst.getTime());   
  
        Calendar firstDateCal = Calendar.getInstance();   
        firstDateCal.setTime(firstDate);   
  
        Calendar c = new GregorianCalendar();   
        c.set(Calendar.YEAR, year);   
        c.set(Calendar.MONTH, Calendar.JANUARY);   
        c.set(Calendar.DATE, firstDateCal.get(Calendar.DATE));   
  
        Calendar cal = (GregorianCalendar) c.clone();   
        cal.add(Calendar.DATE, (week - 1) * 7);   
        firstDate = getFirstDayOfWeek(cal.getTime());   
  
        return firstDate;   
    }   
  
    /** *//**  
     * 取得某年某周的最后一天  
     * 对于交叉:2008-12-29到2009-01-04属于2008年的最后一周,2009-01-04为2008年最后一周的最后一天  
     * @param year  
     * @param week  
     * @return  
     */  
    public static Date getLastDayOfWeek(int year, int week) {   
        Calendar calLast = Calendar.getInstance();   
        calLast.set(year, 0, 7);   
        Date firstDate = getLastDayOfWeek(calLast.getTime());   
  
        Calendar firstDateCal = Calendar.getInstance();   
       firstDateCal.setTime(firstDate);   
  
        Calendar c = new GregorianCalendar();   
        c.set(Calendar.YEAR, year);   
        c.set(Calendar.MONTH, Calendar.JANUARY);   
        c.set(Calendar.DATE, firstDateCal.get(Calendar.DATE));   
  
        Calendar cal = (GregorianCalendar) c.clone();   
        cal.add(Calendar.DATE, (week - 1) * 7);   
        Date lastDate = getLastDayOfWeek(cal.getTime());   
           
        return lastDate;   
    }   
}