java获得日期之间的差值，java获得日期差值,import java.

java获得日期之间的差值，java获得日期差值,import java.

import java.text.*;import java.util.*;public class DateUtils {  public enum IntervalType {  Month, Week  }  private DateUtils() {  }  public static Calendar[] getDateIntervals(IntervalType type, Calendar reference) {    if (reference == null) {      reference = Calendar.getInstance();    }    Calendar startDate = (Calendar)reference.clone();    Calendar endDate = (Calendar)reference.clone();    if (type == IntervalType.Month) {      // first date of the month      startDate.set(Calendar.DATE, 1);      // previous month      startDate.add(Calendar.MONTH, -1);      // first date of the month      endDate.set(Calendar.DATE, 1);      // previous month, last date      endDate.add(Calendar.DATE, -1);    }    else {      // previous week by convention (monday ... sunday)      // you will have to adjust this a bit if you want      // sunday to be considered as the first day of the week.      //   start date : decrement until first sunday then       //   down to monday        int dayOfWeek = startDate.get(Calendar.DAY_OF_WEEK);      while (dayOfWeek  != Calendar.SUNDAY) {        startDate.add(Calendar.DATE, -1);        dayOfWeek = startDate.get(Calendar.DAY_OF_WEEK);      }      while (dayOfWeek != Calendar.MONDAY) {        startDate.add(Calendar.DATE, -1);        dayOfWeek = startDate.get(Calendar.DAY_OF_WEEK);      }      // end date , decrement until the first sunday      dayOfWeek = endDate.get(Calendar.DAY_OF_WEEK);      while (dayOfWeek  != Calendar.SUNDAY) {        endDate.add(Calendar.DATE, -1);        dayOfWeek = endDate.get(Calendar.DAY_OF_WEEK);      }    }    return new Calendar[] { startDate, endDate };   }  public static void main(String[] args) {    try {      SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");      System.out.println("** previous month (relative today)");      Calendar [] results = DateUtils.getDateIntervals(IntervalType.Month, null);      System.out.println(sdf.format(results[0].getTime()));      System.out.println(sdf.format(results[1].getTime()));      System.out.println("** previous week (relative today)");      results = DateUtils.getDateIntervals(IntervalType.Week, null);      System.out.println(sdf.format(results[0].getTime()));      System.out.println(sdf.format(results[1].getTime()));      System.out.println("** previous month (relative jan 1, 2007)");      results = DateUtils.getDateIntervals(IntervalType.Month,         new GregorianCalendar(2007, 00, 1));      System.out.println(sdf.format(results[0].getTime()));      System.out.println(sdf.format(results[1].getTime()));      System.out.println("** previous week (relative jan 1, 2007)");      results = DateUtils.getDateIntervals(IntervalType.Week,         new GregorianCalendar(2007, 00, 1));      System.out.println(sdf.format(results[0].getTime()));      System.out.println(sdf.format(results[1].getTime()));    }    catch (Exception e) {      e.printStackTrace();    }  }

输出：

    ** previous month (relative today)    2008-06-01    2008-06-30    ** previous week (relative today)    2008-06-30    2008-07-06    ** previous month (relative jan 1, 2007)    2006-12-01    2006-12-31    ** previous week (relative jan 1, 2007)    2006-12-25    2006-12-31