Java取一年有多少周、某周的第一天和最后一天

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import java.text.SimpleDateFormat;  

import java.util.Calendar;  

import java.util.Date;  

import java.util.GregorianCalendar;  

public class WeekUtils {  

  

 // 获取当前时间所在年的周数  

 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);  

 }  

  

 // 获取当前时间所在年的最大周数  

 public static int getMaxWeekNumOfYear(int year) {  

  Calendar c = new GregorianCalendar();  

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

  

  return getWeekOfYear(c.getTime());  

 }  

  

 // 获取某年的第几周的开始日期  

 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());  

 }  

  

 // 获取某年的第几周的结束日期  

 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());  

 }  

  

 // 获取当前时间所在周的开始日期  

 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();  

 }  

  

 // 获取当前时间所在周的结束日期  

 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();  

 }  

  

 public static void main(String[] args) {  

  int year = 2011;  

  int week = 1;  

  

  SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");  

  Date today = new Date();  

  Calendar c = new GregorianCalendar();  

  c.setTime(today);  

  

  System.out.println("current date = " + sdf.format(today));  

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

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

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

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

  System.out.println("getFirstDayOfWeek = " + sdf.format(getFirstDayOfWeek(today)));  

  System.out.println("getLastDayOfWeek = " + sdf.format(getLastDayOfWeek(today)));  

 }  

}  
转自:http://blog.csdn.net/dragon1984456/article/details/7094473