科特林的日期和时间

Question

我是科特林新手。我遇到了一个问题。

我有这个代码：

val sdf = SimpleDateFormat("dd.MM.yyyy")
val currentDate = sdf.format(Date())
println(currentDate)

val stringDate = "12.03.2015"
val dateFormatter = DateTimeFormatter.ofPattern("dd.MM.yyyy", Locale.ENGLISH)
val millisecondsSinceEpoch = LocalDate.parse(stringDate, dateFormatter)
    .atStartOfDay(ZoneOffset.UTC)
    .toInstant()
    .toEpochMilli()
println(millisecondsSinceEpoch)

val time = currentDate - millisecondsSinceEpoch
val Datee = sdf.format(time)
println(Datee)

但上线了：

val time = currentDate - millisecondsSinceEpoch
val Datee = sdf.format(time)
println(Datee)

我收到错误：

java.lang.IllegalArgumentException: Cannot format given Object as a Date

请帮助我如何解决这个问题。我需要从字符串中的日期中减去当前日期。

更新：

如何正确地从一个日期减去另一个日期并得到天数差异？

Answer 1

我建议您从过时的java.util日期/时间 API 切换到现代的日期/时间 API。下面给出的是满足您需求的 Java 代码，我希望您能够将其转换为 Kotlin。但是，如果您遇到任何问题，我可以为您将其转换为 Kotlin 代码。

import java.time.Duration;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.Period;
import java.time.ZoneId;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Locale;

public class Main {
    public static void main(String[] args) {
        // Define format
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd.MM.yyyy", Locale.ENGLISH);

        // Given date-time
        ZonedDateTime givenDateTime = LocalDateTime.of(LocalDate.parse("12.03.2015", formatter), LocalTime.of(0, 0))
                .atZone(ZoneId.of("Etc/UTC"));

        // Now
        ZonedDateTime zdtNow = ZonedDateTime.now(ZoneId.of("Etc/UTC"));

        // Period between the two dates
        Period period = Period.between(givenDateTime.toLocalDate(), zdtNow.toLocalDate());

        // Given date-time with current year, month and day
        ZonedDateTime adjusted = givenDateTime.with(LocalDate.now(ZoneId.of("Etc/UTC")));

        // Duration between the two times
        Duration duration = Duration.between(adjusted, zdtNow);

        // Display each part of the period and duration
        System.out.printf("%d years %d month %d days %d hours %d minutes %d seconds %d nanoseconds", period.getYears(),
                period.getMonths(), period.getDays(), duration.toHoursPart(), duration.toMinutesPart(),
                duration.toSecondsPart(), duration.toNanosPart());
    }
}

输出：

5 years 4 month 7 days 19 hours 30 minutes 37 seconds 507058000 nanoseconds

使用OffsetDateTime：

import java.time.Duration;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.OffsetDateTime;
import java.time.Period;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;
import java.util.Locale;

public class Main {
    public static void main(String[] args) {
        // Define format
        DateTimeFormatter formatter = DateTimeFormatter.ofPattern("dd.MM.yyyy", Locale.ENGLISH);

        // Given date-time
        OffsetDateTime givenDateTime = LocalDateTime.of(LocalDate.parse("12.03.2015", formatter), LocalTime.of(0, 0))
                .atOffset(ZoneOffset.UTC);

        // Now
        OffsetDateTime odtNow = OffsetDateTime.now(ZoneOffset.UTC);

        // Period between the two dates
        Period period = Period.between(givenDateTime.toLocalDate(), odtNow.toLocalDate());

        // Given date-time with current year, month and day
        OffsetDateTime adjusted = givenDateTime.with(LocalDate.now(ZoneOffset.UTC));

        // Duration between the two times
        Duration duration = Duration.between(adjusted, odtNow);

        // Display each part of the period and duration
        System.out.printf("%d years %d month %d days %d hours %d minutes %d seconds %d nanoseconds", period.getYears(),
                period.getMonths(), period.getDays(), duration.toHoursPart(), duration.toMinutesPart(),
                duration.toSecondsPart(), duration.toNanosPart());
    }
}