Joda Time：计算一个月内下一个完整间隔的时间

Question

我正在实现一个应用程序，用户可以在其中创建具有截止日期的任务并重复它们，例如每 x 天、每 x 周、每 x 个月重复一次。

当任务到期时，我想根据定义的时间间隔计算下一个（重复的）到期日期。我的实施几周有效，但几个月无效，因为我无法将几个月转换为分钟。

AlarmHelper.java

// Works
static LocalDateTime getNextWeeklyIntervalDate(LocalDateTime creationTime, LocalDateTime dueTime, int intervalInWeeks) {
    int intervalInMinutes = Weeks.weeks(intervalInWeeks).toStandardMinutes().getMinutes();
    int timePassed = Minutes.minutesBetween(creationTime, dueTime).getMinutes();
    int rest = timePassed % intervalInMinutes;
    int minutesToNextFullInterval = intervalInMinutes - rest;
    return dueTime.plusMinutes(minutesToNextFullInterval );
}

// How to implement this analogous to weekly, but for monthly intervals? toStandardMinutes() does not exist for months  
static LocalDateTime getNextMonthlyIntervalDate(LocalDateTime creationTime, LocalDateTime dueTime, int intervalInMonth) {
    int intervalInMinutes = Months.months(intervalInMonth).toStandardMinutes().getMinutes(); // toStandardMinutes() does not exist
}

AlarmHelperTest.java

// User created the task on 01.01.2021 (January 1st, 2021) and want to repeat it weekly.
// So the intervals are 08.01.2021, 15.01.2021 etc.
// In the test the task is due on 12.01.2021, which means the next weekly interval is fulfilled on 15.01.2021.

//The test passes
 @Test
 public void TestGetNextWeeklyIntervalDate() {
    LocalDateTime creation = createLocalDateTime("01.01.2021 06:30:00");
    LocalDateTime due = createLocalDateTime("12.01.2021 05:30:00");
    LocalDateTime expected = createLocalDateTime("15.01.2021 06:30:00");
    LocalDateTime result = AlarmHelper.getNextWeeklyIntervalDate(creation, due, 1);
    assertEquals(expected, result);
}

Answer 1

注意：在Home Page of Joda-Time查看以下通知

Joda-Time 是 Java 的事实上的标准日期和时间库 在 Java SE 8 之前。现在要求用户迁移到 java.time (JSR-310)。

因此，我建议您使用java.time API 使用以下方法：

1. LocalDateTime#isBefore
2. LocalDateTime#plusWeeks
3. LocalDateTime#plusMonths

使用java.time API：

import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Locale;

public class Main {
    public static void main(String[] args) {
        LocalDateTime creation = createLocalDateTime("01.01.2021 06:30:00");
        LocalDateTime due = createLocalDateTime("12.01.2021 05:30:00");
        System.out.println(getNextWeeklyIntervalDate(creation, due, 1));
        System.out.println(getNextMonthlyIntervalDate(creation, due, 1));
    }

    static LocalDateTime getNextWeeklyIntervalDate(LocalDateTime creationTime, LocalDateTime dueTime,
            int intervalInWeeks) {
        LocalDateTime ldt = creationTime;
        while (ldt.isBefore(dueTime)) {
            ldt = ldt.plusWeeks(intervalInWeeks);
        }
        return ldt;
    }

    static LocalDateTime getNextMonthlyIntervalDate(LocalDateTime creationTime, LocalDateTime dueTime,
            int intervalInMonth) {
        LocalDateTime ldt = creationTime;
        while (ldt.isBefore(dueTime)) {
            ldt = ldt.plusMonths(intervalInMonth);
        }
        return ldt;
    }

    static LocalDateTime createLocalDateTime(String dateTimeStr) {
        return LocalDateTime.parse(dateTimeStr, DateTimeFormatter.ofPattern("dd.MM.yyyy HH:mm:ss", Locale.ENGLISH));
    }
}

输出：

2021-01-15T06:30
2021-02-01T06:30

这些方法在 Joda-time API 中也可用，即您只需要更改日期时间字符串的解析方式和获取LocalDateTime 的方式。

使用 Joda-time API：

import org.joda.time.LocalDateTime;
import org.joda.time.format.DateTimeFormat;
import org.joda.time.format.DateTimeFormatter;

public class Main {
    public static void main(String[] args) {
        LocalDateTime creation = createLocalDateTime("01.01.2021 06:30:00");
        LocalDateTime due = createLocalDateTime("12.01.2021 05:30:00");
        System.out.println(getNextWeeklyIntervalDate(creation, due, 1));
        System.out.println(getNextMonthlyIntervalDate(creation, due, 1));
    }

    static LocalDateTime getNextWeeklyIntervalDate(LocalDateTime creationTime, LocalDateTime dueTime,
            int intervalInWeeks) {
        LocalDateTime ldt = creationTime;
        while (ldt.isBefore(dueTime)) {
            ldt = ldt.plusWeeks(intervalInWeeks);
        }
        return ldt;
    }

    static LocalDateTime getNextMonthlyIntervalDate(LocalDateTime creationTime, LocalDateTime dueTime,
            int intervalInMonth) {
        LocalDateTime ldt = creationTime;
        while (ldt.isBefore(dueTime)) {
            ldt = ldt.plusMonths(intervalInMonth);
        }
        return ldt;
    }

    static LocalDateTime createLocalDateTime(String dateTimeStr) {
        DateTimeFormatter dtf = DateTimeFormat.forPattern("dd.MM.yyyy HH:mm:ss");
        LocalDateTime ldt = dtf.parseDateTime(dateTimeStr).toLocalDateTime();
        return ldt;
    }
}

输出：

2021-01-15T06:30:00.000
2021-02-01T06:30:00.000

如您所见，除了createLocalDateTime 中的代码外，java.time 和 Joda-time API 的所有内容都是相同的。