Java:如何获得下一次匹配模式的时间
有没有一种简单/直接的方法可以使用DateTimeFormatter模式来获取与该模式匹配的下一个LocalDateTime时间 我想用它来轻松获得下一次事件发生的时间(可以是每天、每周、每月等)。例如,如果某个事件发生在“周一12:00 AM”,我希望获得下周一12:00 AM的LocalDateTimeJava:如何获得下一次匹配模式的时间,java,datetime,datetimeformatter,Java,Datetime,Datetimeformatter,有没有一种简单/直接的方法可以使用DateTimeFormatter模式来获取与该模式匹配的下一个LocalDateTime时间 我想用它来轻松获得下一次事件发生的时间(可以是每天、每周、每月等)。例如,如果某个事件发生在“周一12:00 AM”,我希望获得下周一12:00 AM的LocalDateTime /**Get next LocalDateTime that matches this input * * @param input a String for
/**Get next LocalDateTime that matches this input
*
* @param input a String for time matching the pattern: [dayOfWeek ][dayOfMonth ][month ][year ]<timeOfDay> <AM/PM>
* @return LocalDateTime representing the next time that matches the input*/
public LocalDateTime getNextTime(String input) {
LocalDateTime currentTime = LocalDateTime.now();
DateTimeFormatter format = DateTimeFormatter.ofPattern("[eeee ][d ][MMMM ][u ]h:m a");
TemporalAccessor accessor = format.parse(input);
// TODO somehow get the next time (that's after currentTime) that matches this pattern
// LocalDateTime time = ???
return time;
}
如果您的输入格式正确且始终为英语,您可以在第一个空格处拆分输入并按如下方式使用:
import java.time.DayOfWeek;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.format.DateTimeFormatter;
import java.time.temporal.TemporalAdjusters;
import java.util.Locale;
public class Example {
public static void main(String[] args) {
LocalDateTime desiredDay = getNextDayTime("Friday 12:00 AM");
DateTimeFormatter dtf = DateTimeFormatter.ofPattern("dd.MM.yyyy hh:mm a");
System.out.println(dtf.format(desiredDay));
}
public static LocalDateTime getNextDayTime(String input){
String[] splited = input.split(" ", 2);
LocalTime localTime = LocalTime.parse(splited[1], DateTimeFormatter.ofPattern("hh:mm a", Locale.US));
LocalDateTime dateTime = LocalDateTime.now().with(localTime);
LocalDateTime desiredDay = dateTime.with(TemporalAdjusters.next(DayOfWeek.valueOf(splited[0].toUpperCase())));
return desiredDay;
}
}
不,没有一种简单或直接的方法可以满足你的要求。它需要相当多的编码。你基本上有16个病例,因为每年、每个月、每个月的每一天和每个星期的每一天都可能存在,也可能不存在。你或多或少得分别处理每一个案子 下一次也可能没有这样的机会。如果这一年是2019年,那就没有了。如果字符串为2021年1月12日星期五凌晨2:00,则不会出现,因为1月12日是星期二,而不是星期五
private static DateTimeFormatter format = DateTimeFormatter
.ofPattern("[eeee ][uuuu ][d ][MMMM ][uuuu ]h:m a", Locale.ENGLISH);
// input = [dayOfWeek] [dayOfMonth] [month] [year] <timeOfDay> <AM/PM>
public static LocalDateTime next(String text) {
TemporalAccessor accessor;
try {
accessor = format.parse(text);
} catch (DateTimeParseException dtpe) {
return null;
}
LocalDateTime now = LocalDateTime.now(ZoneId.systemDefault());
LocalTime parsedTime = LocalTime.from(accessor);
LocalDate earliest = now.toLocalDate();
if (parsedTime.isBefore(now.toLocalTime())) {
earliest = earliest.plusDays(1);
}
return resolveYearMonthDomDow(earliest, accessor).atTime(parsedTime);
}
private static LocalDate resolveYearMonthDomDow(LocalDate earliest, TemporalAccessor accessor) {
if (accessor.isSupported(ChronoField.YEAR)) {
Year parsedYear = Year.from(accessor);
if (parsedYear.isBefore(Year.from(earliest))) {
return null;
}
return resolveMonthDomDow(parsedYear, earliest, accessor);
} else {
Year candidateYear = Year.from(earliest);
while (true) {
LocalDate resolved = resolveMonthDomDow(candidateYear, earliest, accessor);
if (resolved != null) {
return resolved;
}
candidateYear = candidateYear.plusYears(1);
}
}
}
private static LocalDate resolveMonthDomDow(Year year, LocalDate earliest, TemporalAccessor accessor) {
if (accessor.isSupported(ChronoField.MONTH_OF_YEAR)) {
YearMonth knownYm = year.atMonth(accessor.get(ChronoField.MONTH_OF_YEAR));
if (knownYm.isBefore(YearMonth.from(earliest))) {
return null;
}
return resolveDomDow(knownYm, earliest, accessor);
} else {
YearMonth candidateYearMonth = YearMonth.from(earliest);
if (candidateYearMonth.getYear() < year.getValue()) {
candidateYearMonth = year.atMonth(Month.JANUARY);
}
while (candidateYearMonth.getYear() == year.getValue()) {
LocalDate resolved = resolveDomDow(candidateYearMonth, earliest, accessor);
if (resolved != null) {
return resolved;
}
candidateYearMonth = candidateYearMonth.plusMonths(1);
}
return null;
}
}
private static LocalDate resolveDomDow(YearMonth ym, LocalDate earliest, TemporalAccessor accessor) {
if (accessor.isSupported(ChronoField.DAY_OF_MONTH)) {
int dayOfMonth = accessor.get(ChronoField.DAY_OF_MONTH);
if (dayOfMonth > ym.lengthOfMonth()) {
return null;
}
LocalDate resolved = ym.atDay(dayOfMonth);
if (resolved.isBefore(earliest)) {
return null;
} else {
return resolveDow(resolved, accessor);
}
} else {
LocalDate candidateDate = earliest;
if (YearMonth.from(earliest).isBefore(ym)) {
candidateDate = ym.atDay(1);
}
while (YearMonth.from(candidateDate).equals(ym)) {
LocalDate resolved = resolveDow(candidateDate, accessor);
if (resolved != null) {
return resolved;
}
candidateDate = candidateDate.plusDays(1);
}
return null;
}
}
private static LocalDate resolveDow(LocalDate date, TemporalAccessor accessor) {
if (accessor.isSupported(ChronoField.DAY_OF_WEEK)) {
if (date.getDayOfWeek().getValue() == accessor.get(ChronoField.DAY_OF_WEEK)) {
return date;
} else {
return null;
}
} else {
return date;
}
}
我刚才跑步时的输出(2021年1月11日星期一晚上):
2021-01-18T00:00
所以下周一。看起来不错
举一个不同的例子,说明闰年得到尊重:
String input = "Wednesday 29 February 12:00 AM";
2040-02-29T00:00
我的代码中很可能有bug,但基本思想是可行的
一天中的时间没有问题。挑战在于日期。我用一天中的时间来确定今天的日期是否是最早的候选日期。如果现在的时间已经超过字符串中的时间,则最早的日期是明天。对于您的示例字符串,周一12:00am
,实际情况总是这样:总是在午夜12点之后
你在
星期一25:00 AM
中有一个模棱两可的地方,因为25可能是一年(几千年前)或一个月中的一天。我坚持用四位数的年份来解决这个问题。因此,如果一周中某一天的开头或后面的数字有四位数字,则表示一年,否则表示一个月中的某一天。我使用的格式化程序看起来很有趣,一年两次。我需要它来强制解析在尝试月日之前尝试年,或者有时需要一个四位数的数字作为月日。这反过来意味着格式化程序接受的格式太多了。我想这在实践中不会是一个问题。所以周一和周一比赛,但周五和周一比赛,而不是周五,我很困惑,我想你需要定义一下“比赛”的含义。你想要下一个工作日的同一时间吗?这对我来说很有意义-有点像Cron-给我下周一12:00的时间,所以现在的答案(至少对我在英国)是2021-01-18T00:00:00如果我不打算睡觉,我会考虑一个答案,但正如前面提到的,我在英国,对我这个年龄的人来说已经晚了。希望不久你会有一个答案。如果输入总是天和时间,我想你可以根据天数做一个简单的加法,但你希望输入是灵活的guess@OneCricketeer[]
可选部分应包含字符:这仅适用于输入匹配EEE h:m a
。我希望这适用于与模式匹配的任何字符串[eeee][d][MMMM][u]h:ma
String input = "Monday 12:00 AM";
// get the next time that matches this pattern
LocalDateTime time = next(input);
System.out.println(time);
String input = "Wednesday 29 February 12:00 AM";