一、Calender:

二、Date：

2.1）String to Date:

  1. public static Date stringToDate(String dateStr, String pattern) throws ParseException {
  2.     SimpleDateFormat format = new SimpleDateFormat(pattern);
  3.     return format.parse(dateStr);
  4. }
  6. //Test:
  7. System.out.println(stringToDate("20220101", "yyyyMMdd"));
  8. System.out.println(stringToDate("2022-01-01", "yyyy-MM-dd"));

2.2）Date to String:

  1. public static String dateToString(Date dateStr, String pattern) throws ParseException {
  2.     SimpleDateFormat format = new SimpleDateFormat(pattern);
  3.     return format.format(dateStr);
  4. }
  6. //Test:
  7. System.out.println(dateToString(new Date(), "yyyyMMdd"));
  8. System.out.println(dateToString(new Date(), "yyyy-MM-dd"));

2.3）加、减

  1. public static Date addDays(Date date, int n) {
  2.     Calendar cal = Calendar.getInstance();
  3.     //设置起时间
  4.     cal.setTime(date);
  5.     //增加天n天
  6.     cal.add(Calendar.DATE, n);
  7.     return cal.getTime();
  8. }
  10. //Test:
  11. System.out.println(addDays(new Date(), -1));
  12. System.out.println(addDays(new Date(), 1));

2.4）日期差

  1. public static int dateDifference(Date start, Date end) {
  2.     Calendar cal = Calendar.getInstance();
  3.     //设置起时间
  4.     cal.setTime(start);
  5.     int n = 0;
  6.     for (;;) {
  7.         //增加天1天
  8.         cal.add(Calendar.DATE, 1);
  9.         n = n + 1;
  10.         if (cal.getTime().compareTo(end) == 0) {
  11.             break;
  12.         }
  13.     }
  14.     return n;
  15. }
  17. //Test:
  18. System.out.println(dateDifference(stringToDate("20220101", "yyyyMMdd"), stringToDate("20220102", "yyyyMMdd")));

2.5）获取两个日期中间的所有日期（包含起始日期）

  2. public static List<Date> getBetweenDate(Date start, Date end) {
  3.     Set<Date> dateSet = new HashSet<>();
  4.     Calendar cal = Calendar.getInstance();
  5.     //设置起时间
  6.     cal.setTime(start);
  7.     int n = 0;
  8.     for (;;) {
  9.         dateSet.add(start);
  10.         //增加天1天
  11.         cal.add(Calendar.DATE, 1);
  12.         n = n + 1;
  13.         if (cal.getTime().compareTo(end) == 0) {
  14.             break;
  15.         }
  16.         dateSet.add(cal.getTime());
  17.     }
  18.     dateSet.add(end);
  19.     List<Date> dateList = new ArrayList<Date>(dateSet);
  20.     Collections.sort(dateList);
  21.     return dateList;
  22. }
  24. //Test:
  25. System.out.println(getBetweenDate(stringToDate("20220101", "yyyyMMdd"), stringToDate("20220102", "yyyyMMdd")));

2.6）获取一周的第一天、最后一天

2.7）获取一月的第一天、最后一天

2.8）获取一年的第一天、最后一天

2.8）大小比较

三、DateTime:

3.1）String to DateTime:

3.2）DateTime to String:

四、LocalDate:

4.1）String to LocalDate:

4.2）LocalDate to String:

五、LocalDateTime:

5.1）String to LocalDate:

5.2）LocalDate to String: