Calendar

Calendar类是一个抽象类，不可以使用new关键字直接创建实例。
Calendar可以为在某一特定时刻和一组之间的转换的方法 calendar fields（日历域） 如YEAR ， MONTH ， DAY_OF_MONTH ， HOUR 等等，以及用于操纵该日历字段，如获取的日期下个星期。

  1. import java.util.Calendar;
  3. /**
  4. * 使用默认时区和区域设置获取日历
  5. */
  6. public class TestCalendar {
  7.     public static void main(String[] args) {
  8.         Calendar ca = Calendar.getInstance();
  9.         // get：返回给定日历字段的值。
  10.         // YEAR：年份
  11.         int year = ca.get(Calendar.YEAR);
  12.         System.out.println(year);
  13.         // MONTH：月份
  14.         System.out.println(ca.get(Calendar.MONTH)+1);
  15.         // DATE：本月的日期
  16.         System.out.println(ca.get(Calendar.DATE));
  17.         // DAY_OF_MONTH：一周中的日期
  18.         System.out.println(ca.get(Calendar.DAY_OF_MONTH));
  19.         // 一个月的第几周
  20.         System.out.println(ca.get(Calendar.DAY_OF_WEEK_IN_MONTH));
  21.         // 一个月的第几天
  22.         System.out.println(ca.get(Calendar.DAY_OF_MONTH));
  23.         // HOUR_OF_DAY：当天的小时数
  24.         System.out.println(ca.get(Calendar.HOUR_OF_DAY));
  25.         // MINUTE：分
  26.         System.out.println(ca.get(Calendar.MINUTE));
  27.         // SECOND：秒
  28.         System.out.println(ca.get(Calendar.SECOND));
  30.         // 注意：静态成员和静态方法不要使用名称来调用，必须使用名称来调用。
  31.         System.out.println(ca.get(ca.SECOND));
  32.         // set：设置日历字段的值
  33.         // set(int field, nt value);
  34.         // field -> 给定的日历字段
  35.         // value -> 要为给定日历字段设置的值
  36.         ca.set(Calendar.YEAR, 2020);
  37.         Date time = ca.getTime();
  38.         System.out.println(time);
  39.         // set(int year, int month, int date, int hourOfDay, int minute, int second);
  40.         // year -> 用于设置 YEAR日历字段的值。
  41.         // month -> 用于设置MONTH日历字段的值。 月值为0。 例如，1月份为0。
  42.         // date -> 用于设置 DAY_OF_MONTH日历字段的值。
  43.         // hourOfDay -> 用于设置 HOUR_OF_DAY日历字段的值。
  44.         // minute -> 用于设置 MINUTE日历字段的值。
  45.         // second -> 用于设置 SECOND日历字段的值。
  46.     }
  47. }

1.获取当月时间范围

  1. public static String getMonth(){
  2.     SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd");
  3.     Calendar c = Calendar.getInstance();
  4.     c.add(Calendar.MONTH, 0);
  5.     c.set(Calendar.DAY_OF_MONTH,1);
  6.     String first = format.format(c.getTime());
  7.     Calendar ca = Calendar.getInstance();
  8.     ca.set(Calendar.DAY_OF_MONTH, ca.getActualMaximum(Calendar.DAY_OF_MONTH));
  9.     String last = format.format(ca.getTime());
  10.     return first+" and "+last;
  11. }

输出:

  1. public static void main(String[] args) {
  2.     System.out.println(getMonth()); // 2019-01-01 and 2019-01-31
  3. }

2.获取去年当月时间范围

  1. public static String getMonthLastYear(){
  2.     SimpleDateFormat format=new SimpleDateFormat("yyyyMMdd");
  3.     Calendar lastYearStart = Calendar.getInstance();
  4.     lastYearStart.add(Calendar.YEAR, -1);
  5.     lastYearStart.add(Calendar.MONTH, 0);
  6.     lastYearStart.set(Calendar.DAY_OF_MONTH,1);
  7.     String firstDayLastYear = format.format(lastYearStart.getTime());
  8.     Calendar lastYearEnd = Calendar.getInstance();
  9.     lastYearEnd.add(Calendar.YEAR, -1);
  10.     lastYearEnd.add(Calendar.MONTH, 0);
  11.     lastYearEnd.set(Calendar.DAY_OF_MONTH, lastYearEnd.getActualMaximum(Calendar.DAY_OF_MONTH));
  12.     String endDayLastYear = format.format(lastYearEnd.getTime());
  13.     return firstDayLastYear+" and "+endDayLastYear;
  14. }

输出:

  1. public static void main(String[] args) {
  2.     System.out.println(getMonthLastYear());// 20180101 and 20180131
  3. }

3. 获取某年某月时间范围

  1. public static String getMonthAround(String date){
  2.     SimpleDateFormat format=new SimpleDateFormat("yyyy-MM");
  3.     SimpleDateFormat format2=new SimpleDateFormat("yyyy-MM-dd");
  4.     Date monthDate = null;
  5.     try {
  6.         monthDate = format.parse(date);
  7.     } catch (ParseException e) {
  8.         e.printStackTrace();
  9.     }
  10.     Calendar lastYearStart = Calendar.getInstance();
  11.     lastYearStart.setTime(monthDate);
  12.     lastYearStart.set(Calendar.DAY_OF_MONTH,1);
  13.     String firstDayLastYear = format2.format(lastYearStart.getTime());
  14.     Calendar lastYearEnd = Calendar.getInstance();
  15.     lastYearEnd.setTime(monthDate);
  16.     lastYearEnd.set(Calendar.DAY_OF_MONTH, lastYearEnd.getActualMaximum(Calendar.DAY_OF_MONTH));
  17.     String endDayLastYear = format2.format(lastYearEnd.getTime());
  18.     return firstDayLastYear+" and "+endDayLastYear;
  19. }

输出:

  1. public static void main(String[] args) {
  2.     System.out.println(getMonthAround("2019-06"));// 2019-06-01 and 2019-06-30
  3. }

4.获取某日去年的时间,如果是闰年二月29号,前一年自动变成28号

  1. public static String getDateDayLastYear(String dateStr){
  2.     SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
  3.     Date date = null;
  4.     try {
  5.         date = format.parse(dateStr);
  6.     } catch (ParseException e) {
  7.         e.printStackTrace();
  8.     }
  9.     Calendar cal = Calendar.getInstance();
  10.     cal.setTime(date);
  11.     cal.add(Calendar.YEAR, -1);
  12.     cal.add(Calendar.MONTH, 0);
  13.     String lastDay = format.format(cal.getTime());
  14.     return lastDay;
  15. }

输出:

  1. public static void main(String[] args) {
  2.     System.out.println(getDateDayLastYear("2019-2-28"));// 2018-02-28
  3. }

5.计算两个日期之间所包含的天数

  1. public static int differentDays(String startDate,String endDate){
  2.     SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd");
  3.     Date date2 = null;
  4.     Date date1 = null;
  5.     try {
  6.         date1 = format.parse(startDate);
  7.         date2 = format.parse(endDate);
  8.     } catch (ParseException e) {
  9.         e.printStackTrace();
  10.     }
  11.     Calendar cal1 = Calendar.getInstance();
  12.     cal1.setTime(date1);
  13.     Calendar cal2 = Calendar.getInstance();
  14.     cal2.setTime(date2);
  15.     int day1= cal1.get(Calendar.DAY_OF_YEAR);
  16.     int day2 = cal2.get(Calendar.DAY_OF_YEAR);
  17.     int year1 = cal1.get(Calendar.YEAR);
  18.     int year2 = cal2.get(Calendar.YEAR);
  19.     if(year1 != year2) {
  20.         int timeDistance = 0 ;
  21.         for(int i = year1 ; i < year2 ; i ++) {
  22.             //闰年
  23.             if(i%4==0 && i%100!=0 || i%400==0){
  24.                 timeDistance += 366;
  25.             } else{    //不是闰年
  26.                 timeDistance += 365;
  27.             }
  28.         }
  29.         return timeDistance + (day2-day1)+1 ;
  30.     } else{    //同年
  31.         return day2-day1+1;
  32.     }
  33. }

输出:

  1. public static void main(String[] args) {
  2.     System.out.println(differentDays("2019-2-26","2019-2-28"));// 3
  3. }

6.获取上个月的第一天和最后一天

  1. public static String getLastMonth(){
  2.     SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd");
  3.     Calendar calendar=Calendar.getInstance();
  4.     calendar.add(Calendar.MONTH, -1);
  5.     calendar.set(Calendar.DAY_OF_MONTH, 1);
  6.     Calendar calendar1=Calendar.getInstance();
  7.     int month=calendar1.get(Calendar.MONTH);
  8.     calendar1.set(Calendar.MONTH, month-1);
  9.     calendar1.set(Calendar.DAY_OF_MONTH,
  10.     calendar1.getActualMaximum(Calendar.DAY_OF_MONTH));
  11.     String firstDay = format.format(calendar.getTime());
  12.     String lastDay = format.format(calendar1.getTime());
  13.     return  firstDay+" and "+lastDay;
  14. }

输出:

  1. public static void main(String[] args) {
  2.     System.out.println(getLastMonth());// 2018-12-01 and 2018-12-31
  3. }

7.获取某个时间的当周时间范围

  1. public static String getWeek(String date){
  2.     SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
  3.     Date time = null;
  4.     try {
  5.          time = sdf.parse(date);
  6.     } catch (ParseException e) {
  7.         e.printStackTrace();
  8.     }
  9.     Calendar cal = Calendar.getInstance();
  10.     cal.setTime(time);
  11.     int dayWeek = cal.get(Calendar.DAY_OF_WEEK);
  12.     if (1 == dayWeek) {
  13.         cal.add(Calendar.DAY_OF_MONTH, -1);
  14.     }
  15.     cal.setFirstDayOfWeek(Calendar.MONDAY);
  16.     int day = cal.get(Calendar.DAY_OF_WEEK);
  17.     cal.add(Calendar.DATE, cal.getFirstDayOfWeek() - day);
  18.     String imptimeBegin = sdf.format(cal.getTime());
  19.     cal.add(Calendar.DATE, 6);
  20.     String imptimeEnd = sdf.format(cal.getTime());
  21.     return imptimeBegin + " and " + imptimeEnd;
  22. }

输出:

  1. public static void main(String[] args) {
  2.     System.out.println(getWeek("2019-01-23"));// 2019-01-21 and 2019-01-27
  3. }

8.指定日期加上天数后的日期

  1. // @param num 为增加的天数
  2. // @param newDate 创建时间
  3. public static String plusDay(int num, String newDate) {
  4.     SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
  5.     Date dt = null;
  6.     try {
  7.         dt = sdf.parse(newDate);
  8.     } catch (ParseException e) {
  9.         e.printStackTrace();
  10.     }
  11.     Calendar rightNow = Calendar.getInstance();
  12.     rightNow.setTime(dt);
  13.     rightNow.add(Calendar.DAY_OF_YEAR, num);
  14.     Date dt1 = rightNow.getTime();
  15.     String reStr = sdf.format(dt1);
  16.     return reStr;
  17. }

输出:

  1. public static void main(String[] args) {
  2.     System.out.println(plusDay(2,"2019-01-23"));//2019-01-25
  3. }

9.指定日期加上月数后的日期

  1. public static String plusMonth(int num, String newDate) {
  2.     SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
  3.     Date dt = null;
  4.     try {
  5.         dt = sdf.parse(newDate);
  6.     } catch (ParseException e) {
  7.         e.printStackTrace();
  8.     }
  9.     Calendar rightNow = Calendar.getInstance();
  10.     rightNow.setTime(dt);
  11.     rightNow.add(Calendar.MONTH,num);//日期加3个月
  12.     Date dt1 = rightNow.getTime();
  13.     String reStr = sdf.format(dt1);
  14.     return reStr;
  15. }

输出:

  1. public static void main(String[] args) {
  2.     System.out.println(plusMonth(12,"2004-02-29"));//2005-02-28
  3. }

10.获取上个月的今天

  1. public static String getFirstDate() {
  2.     SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
  3.     Calendar cl = Calendar.getInstance();
  4.     cl.add(Calendar.MONTH, -1);
  5.     Date dateFrom = cl.getTime();
  6.     return sdf.format(dateFrom);
  7. }

输出:

  1. public static void main(String[] args) {
  2.     System.out.println(getFirstDate());//2018-12-23
  3. }

11.获取某天的下一天

  1. public static String getNextDate(String newDate) {
  2.     SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
  3.     Date dt = null;
  4.     try {
  5.         dt = sdf.parse(newDate);
  6.     } catch (ParseException e) {
  7.         e.printStackTrace();
  8.     }
  9.     Calendar rightNow = Calendar.getInstance();
  10.     rightNow.setTime(dt);
  11.     rightNow.add(Calendar.DATE,1);//日期加1天
  12.     Date dt1 = rightNow.getTime();
  13.     String reStr = sdf.format(dt1);
  14.     return reStr;
  15. }

输出:

  1. public static void main(String[] args) {
  2.     System.out.println(getNextDate("2019-02-20"));//2019-02-21
  3. }