Java 8 日期新特性

转载：https://www.cnblogs.com/binghe001/p/13028868.html

日期格式的互相转换

转载：https://www.cnblogs.com/puke/p/11314431.html

  1. DateTimeFormatter dateTimeFormatter1 = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
  2. DateTimeFormatter dateTimeFormatter2 = DateTimeFormatter.ofPattern("yyyy-MM-dd");
  4. LocalDateTime localDateTime = LocalDateTime.parse("2019-07-31 00:00:00",dateTimeFormatter1);
  5. LocalDate localDate = LocalDate.parse("2019-07-31",dateTimeFormatter2);
  6. Date date = Date.from(LocalDateTime.parse("2019-07-31 00:00:00",dateTimeFormatter1).atZone(ZoneId.systemDefault()).toInstant());
  9. String strDateTime = "2019-07-31 00:00:00";
  10. String strDate = "2019-07-31";
  11. Long timestamp=1564502400000l;
  13. /** LocalDateTime 转 LocalDate */
  14. System.out.println("LocalDateTime 转 LocalDate: "+localDateTime.toLocalDate());
  15. /** LocalDateTime 转 Long */
  16. System.out.println("LocalDateTime 转 Long: "+localDateTime.atZone(ZoneId.systemDefault()).toInstant().toEpochMilli());
  17. /** LocalDateTime 转 Date */
  18. System.out.println("LocalDateTime 转 Date: "+Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant()));
  19. /** LocalDateTime 转 String */
  20. System.out.println("LocalDateTime 转 String: "+localDateTime.format(dateTimeFormatter1));
  22. System.out.println("-------------------------------");
  24. /** LocalDate 转 LocalDateTime */
  25. System.out.println("LocalDate 转 LocalDateTime: "+LocalDateTime.of(localDate,LocalTime.parse("00:00:00")));
  26. /** LocalDate 转 Long */
  27. System.out.println("LocalDate 转 Long: "+localDate.atStartOfDay(ZoneId.systemDefault()).toInstant().toEpochMilli());
  28. /** LocalDate 转 Date */
  29. System.out.println("LocalDate 转 Date: "+Date.from(localDate.atStartOfDay().atZone(ZoneId.systemDefault()).toInstant()));
  30. /** LocalDate 转 String */
  31. System.out.println("LocalDateTime 转 String: "+localDateTime.format(dateTimeFormatter2));
  33. System.out.println("-------------------------------");
  35. /** Date 转 LocalDateTime */
  36. System.out.println("Date 转 LocalDateTime: "+LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault()));
  37. /** Date 转 Long */
  38. System.out.println("Date 转 Long: "+date.getTime());
  39. /** Date 转 LocalDate */
  40. System.out.println("Date 转 LocalDate: "+LocalDateTime.ofInstant(date.toInstant(), ZoneId.systemDefault()).toLocalDate());
  41. /** Date 转 String */
  42. SimpleDateFormat sdf =new SimpleDateFormat("yyyy-MM-dd HH:mm:ss SSS" );
  43. System.out.println("Date 转 String: "+sdf.format(date));
  45. System.out.println("-------------------------------");
  47. /** String 转 LocalDateTime */
  48. System.out.println("String 转 LocalDateTime: "+LocalDateTime.parse(strDateTime,dateTimeFormatter1));
  49. /** String 转 LocalDate */
  50. System.out.println("String 转 LocalDate: "+LocalDateTime.parse(strDateTime,dateTimeFormatter1).toLocalDate());
  51. System.out.println("String 转 LocalDate: "+LocalDate.parse(strDate,dateTimeFormatter2));
  52. /** String 转 Date */
  53. System.out.println("String 转 Date: "+Date.from(LocalDateTime.parse(strDateTime,dateTimeFormatter1).atZone(ZoneId.systemDefault()).toInstant()));
  55. System.out.println("-------------------------------");
  57. /** Long 转 LocalDateTime */
  58. System.out.println("Long 转 LocalDateTime:"+LocalDateTime.ofInstant(Instant.ofEpochMilli(timestamp), ZoneId.systemDefault()));
  59. /** Long 转 LocalDate */
  60. System.out.println("Long 转 LocalDate:"+LocalDateTime.ofInstant(Instant.ofEpochMilli(timestamp), ZoneId.systemDefault()).toLocalDate());
  62.  LocalDateTime now = LocalDateTime.now();//2020-09-11T09:41:01.547
  63.         LocalDateTime DiscountStartTime = now.minusDays(3);//减法 2020-09-08T09:41:01.547
  64.         LocalDateTime DiscountEndTime = now.plusDays(3);//加法 2020-09-14T09:41:01.547
  66. //        now>DiscountStartTime && DiscountEndTime>now
  67. //        DiscountEndTime>now>DiscountStartTime
  68.         if(now.isAfter(DiscountStartTime) && DiscountEndTime.isAfter(now)){
  69.             true;//输出true
  70.         }

日期处理

  1.     @Test
  2.     public void contextLoads() {
  3.         LocalDate today = LocalDate.now();  // 当前日期 年 月 日
  4.         LocalTime minTime = LocalTime.MIN;  // 最小时间 00:00:00
  6.         LocalDate twoDaysLaterDate = today.plusDays(2); // 两天之后的日期 年 月 日
  7.         LocalTime maxTime = LocalTime.MAX;  // 最大时间 23:59:59
  9.         // 将日期和时间组合起来，并转换成想要的格式
  10.         String beginDate = LocalDateTime.of(today, minTime).format(DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss"));
  11.         String endDate = LocalDateTime.of(twoDaysLaterDate, maxTime).format(DateTimeFormatter
  12.                 .ofPattern("yyyy-MM-dd HH:mm:ss"));
  14.         System.out.println("开始时间：" + beginDate);
  15.         System.out.println("结束时间：" + endDate);
  16.     }

获得一个月最大天数的方法（备忘）

转载：https://www.cnblogs.com/relucent/p/4566582.html

获取某段时间内的周几的日期

  1.     /**
  2.      * 获取某段时间内的周几的日期
  3.      *
  4.      * @param dataBegin 开始日期
  5.      * @param dataEnd   结束日期
  6.      * @param weekDays  获取周几，1－6代表周一到周六。0代表周日
  7.      * @return 返回日期List
  8.      */
  9.     public static List<String> getDayOfWeekWithinDateInterval(String dataBegin, String dataEnd, int weekDays) {
  10.         SimpleDateFormat sd = new SimpleDateFormat("yyyy-MM-dd");
  11.         List<String> dateResult = new ArrayList<>();
  12.         Calendar cal = Calendar.getInstance();
  13.         String[] dateInterval = {dataBegin, dataEnd};
  14.         Date[] dates = new Date[dateInterval.length];
  15.         for (int i = 0; i < dateInterval.length; i++) {
  16.             String[] ymd = dateInterval[i].split("[^\\d]+");
  17.             cal.set(Integer.parseInt(ymd[0]), Integer.parseInt(ymd[1]) - 1, Integer.parseInt(ymd[2]));
  18.             dates[i] = cal.getTime();
  19.         }
  20.         for (Date date = dates[0]; date.compareTo(dates[1]) <= 0; ) {
  21.             cal.setTime(date);
  22.             if (cal.get(Calendar.DAY_OF_WEEK) - 1 == weekDays) {
  23.                 String format = sd.format(date);
  24.                 dateResult.add(format);
  25.             }
  26.             cal.add(Calendar.DATE, 1);
  27.             date = cal.getTime();
  28.         }
  29.         return dateResult;
  30.     }

获取两个指定日期之间的所有月份

转载：https://www.cnblogs.com/beanbag/p/9719907.html

  1. public void getAmongstMonth() {
  2.         String y1 = "2022-03";// 开始时间
  3.         String y2 = "2022-05";// 结束时间
  5.         try {
  6.             Date startDate = new SimpleDateFormat("yyyy-MM").parse(y1);
  7.             Date endDate = new SimpleDateFormat("yyyy-MM").parse(y2);
  9.             Calendar calendar = Calendar.getInstance();
  10.             calendar.setTime(startDate);
  11.             // 获取开始年份和开始月份
  12.             int startYear = calendar.get(Calendar.YEAR);
  13.             int startMonth = calendar.get(Calendar.MONTH);
  14.             // 获取结束年份和结束月份
  15.             calendar.setTime(endDate);
  16.             int endYear = calendar.get(Calendar.YEAR);
  17.             int endMonth = calendar.get(Calendar.MONTH);
  18.             //
  19.             List<String> list = new ArrayList<String>();
  20.             for (int i = startYear; i <= endYear; i++) {
  21.                 String date = "";
  22.                 if (startYear == endYear) {
  23.                     for (int j = startMonth; j <= endMonth; j++) {
  24.                         if (j < 9) {
  25.                             date = i + "-0" + (j + 1);
  26.                         } else {
  27.                             date = i + "-" + (j + 1);
  28.                         }
  29.                         list.add(date);
  30.                     }
  32.                 } else {
  33.                     if (i == startYear) {
  34.                         for (int j = startMonth; j < 12; j++) {
  35.                             if (j < 9) {
  36.                                 date = i + "-0" + (j + 1);
  37.                             } else {
  38.                                 date = i + "-" + (j + 1);
  39.                             }
  40.                             list.add(date);
  41.                         }
  42.                     } else if (i == endYear) {
  43.                         for (int j = 0; j <= endMonth; j++) {
  44.                             if (j < 9) {
  45.                                 date = i + "-0" + (j + 1);
  46.                             } else {
  47.                                 date = i + "-" + (j + 1);
  48.                             }
  49.                             list.add(date);
  50.                         }
  51.                     } else {
  52.                         for (int j = 0; j < 12; j++) {
  53.                             if (j < 9) {
  54.                                 date = i + "-0" + (j + 1);
  55.                             } else {
  56.                                 date = i + "-" + (j + 1);
  57.                             }
  58.                             list.add(date);
  59.                         }
  60.                     }
  62.                 }
  64.             }
  66.             // 所有的月份已经准备好
  67.             //System.out.println(list);
  68.             for (int i = 0; i < list.size(); i++) {
  69.                 System.out.println(list.get(i));
  70.             }
  71.             System.out.println("里面有" + list.size() + "个月份");
  73.         } catch (Exception e) {
  74.             e.printStackTrace();
  75.         }
  76.     }

对当前时间进行加减

  1.     // 将分钟转换为毫秒
  2.     int fiveMinutes = 5 * 60 * 1000;
  4.     Date now = new Date();
  6.     // 5分钟之后
  7.     Date fiveMinutesAgo = new Date(now.getTime() + fiveMinutes);
  9.     // 5分钟之前
  10.     Date fiveMinutesAgo = new Date(now.getTime() - fiveMinutes);

两个日期中间有多少天

  1.     /**
  2.      * 两个日期中间有多少天
  3.      *
  4.      * @param startDate
  5.      * @param endDate
  6.      * @return
  7.      */
  8.     public static Long getAmongstDays(Date startDate, Date endDate) {
  9.         long intervalMills = endDate.getTime() - startDate.getTime();
  10.         return intervalMills / (1000 * 60 * 60 * 24);
  11.     }