java 日历工具类（计算周的开始日期和结束日期，以及包好的日期）

package com.zxy.product.training.web.util;

import java.text.ParseException;

import java.text.SimpleDateFormat;

import java.util.ArrayList;

import java.util.Calendar;

import java.util.List;

public class WeekUtil {
/** 

     * 获取指定年份日历

     * @param year 

     * @return 

     */  

    private static Calendar getCalendarFormYear(int year){  

        Calendar cal = Calendar.getInstance();  

        cal.set(Calendar.DAY_OF_WEEK, Calendar.MONDAY);        

        cal.set(Calendar.YEAR, year);  

        return cal;  

    }  
/** 

     * 获取指定年指定周的开始日期

     * @param year 

     * @param weekNo 

     * @return 

     */  

    public static String getStartDayOfWeekNo(int year,int weekNo){  

        Calendar cal = getCalendarFormYear(year);  

        cal.set(Calendar.WEEK_OF_YEAR, weekNo);

        int month = cal.get(Calendar.MONTH) + 1;

        int day = cal.get(Calendar.DAY_OF_MONTH);

        String monthStr = null;

        String dayStr = null;

        StringBuilder monthBuilder = new StringBuilder();

        StringBuilder dayBuilder = new StringBuilder();

        if(month < 10){

        monthStr = monthBuilder.append("0").append(month).toString();

        } else {

        monthStr = monthBuilder.append(month).toString();

        }

        if(day < 10) {

        dayStr = dayBuilder.append("0").append(day).toString();

        } else {

        dayStr = dayBuilder.append(day).toString();

        }

        return cal.get(Calendar.YEAR) + "-" + monthStr + "-" + dayStr;     

          

    }  

      

    /** 

     * 获取指定年指定周的结束日期

     * @param year 

     * @param weekNo 

     * @return 

     */  

    public static String getEndDayOfWeekNo(int year,int weekNo){  

        Calendar cal = getCalendarFormYear(year);  

        cal.set(Calendar.WEEK_OF_YEAR, weekNo);  

        cal.add(Calendar.DAY_OF_WEEK, 6); 

        int month = cal.get(Calendar.MONTH) + 1;

        int day = cal.get(Calendar.DAY_OF_MONTH);

        String monthStr = null;

        String dayStr = null;

        StringBuilder monthBuilder = new StringBuilder();

        StringBuilder dayBuilder = new StringBuilder();

        if(month < 10){

        monthStr = monthBuilder.append("0").append(month).toString();

        } else {

        monthStr = monthBuilder.append(month).toString();

        }

        if(day < 10) {

        dayStr = dayBuilder.append("0").append(day).toString();

        } else {

        dayStr = dayBuilder.append(day).toString();

        }

        return cal.get(Calendar.YEAR) + "-" + monthStr + "-" +  dayStr;      

    }  

    //获取 某日是某年的第几周

    public static int getWeekByDay(String day) throws ParseException {

         SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");

         Calendar calendar = Calendar.getInstance();

         calendar.setFirstDayOfWeek(Calendar.SUNDAY);

         calendar.setTime(format.parse(day));

        return calendar.get(Calendar.WEEK_OF_YEAR);

  }

    

    //获取 指定开始日期和结束日期，包含日期列表。

   public static List<String> getDays(String beginDate, String endDate) throws ParseException {
  List<String> result = new ArrayList<String>();
  SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");  

       Calendar calendar = Calendar.getInstance();  

       calendar.setTime(format.parse(beginDate));  

 

       for (long  time= calendar.getTimeInMillis(); time <= format.parse(endDate).getTime(); time = getNextDay(calendar)) {  

      result.add(format.format(time));  

       }  
  return result;

   }

   

   public static long getNextDay(Calendar calendar) {  
  calendar.set(Calendar.DAY_OF_MONTH, calendar.get(Calendar.DAY_OF_MONTH) + 1);  

       return calendar.getTimeInMillis();  

   } 

    

  /**

 * @param args

 * @throws ParseException

 */

public static void main(String[] args) throws ParseException{
 String day = "2016-12-31";
int week = WeekUtil.getWeekByDay(day);

System.out.println("第"+week+"周");
System.out.println("第"+week+"周开始日期："+WeekUtil.getStartDayOfWeekNo(2016, week));
System.out.println("第"+week+"周结束日期："+WeekUtil.getEndDayOfWeekNo(2016, week));

String beginDate = WeekUtil.getStartDayOfWeekNo(2016, week);
String endDate = WeekUtil.getEndDayOfWeekNo(2016, week);

WeekUtil.getDays(beginDate,endDate).stream().forEach(item -> System.out.println("日期:"+item));

  }

}