英文:
How to change just the time of the Date object in Java leaving the date information intact
问题
public static Date adjustTimeOfDay(Date deliveryDate, String timeOfDay) {// 将交付日期的时间部分进行调整，基于给定的时间字符串 timeOfDay// 在调整时保持偏移量和时区不变return adjustedDeliveryDate; // 返回调整后的交付日期}
英文:
I have a Date variable lets say deliveryDate. It's saved in MonngoDB in this format.
ISODate("2020-10-07T03:10:00Z")
Now I want to change the time property of delivery Date. But it has to be done based on some String which tells what time to be set. for eg String time = "7:20 AM" [ this time is based of Kuala Lumpur, Malaysia ]. Then the result should be something like :
deliveryDate = ISODate("2020-10-07T11:20:00Z")
Some general note : 7:20 AM Monday, in Kuala Lumpur, Federal Territory of Kuala Lumpur, Malaysia is 11:20 PM Sunday, Coordinated Universal Time (UTC).
Now given the String time and Date delivery Date. How can I obtain the results above for all cases ?
The thing that I am expecting is :
public static Date adjustTimeOfDay(Date deliveryDate, String timeOfDay) {// Adjust the time of the day of deliveryDate on the basis of timeOfDay// Keep the offset and zone same while adjustingreturn deliveryDate}
答案1
得分: 2
你可以使用兼容性方法 java.util.Date.toInstant()，操作该 Instant 的时间部分，从而创建一个不同的 Instant，然后通过 Date.from(Instant instant) 转换回一个 Date。
下面是一个用于操作的示例方法：
public static Instant adjustTimeOfDay(Instant instant, String timeOfDay) {// 将 instant 转换为带有偏移的日期时间对象OffsetDateTime deliveryOdt = OffsetDateTime.ofInstant(instant, ZoneOffset.UTC);/** 提供一个解析时间字符串的格式化器。* 请注意，这个格式化器不是非常宽松的，* 字符串必须符合 "hh:mm a" 模式。*/DateTimeFormatter dtf = new DateTimeFormatterBuilder().appendPattern("hh").appendLiteral(':').appendPattern("mm").appendLiteral(' ').appendPattern("a").parseCaseInsensitive().toFormatter();// 将该字符串解析为 LocalTimeLocalTime localTime = LocalTime.parse(timeOfDay, dtf);/** 创建一个新的 OffsetDateTime，* 将新的 LocalTime 添加到旧的 UTC 日期上*/OffsetDateTime adjustedOdt = OffsetDateTime.of(deliveryOdt.toLocalDate(),localTime,ZoneOffset.UTC);return adjustedOdt.toInstant();}
我在类似以下的 main 方法中使用了它：
public static void main(String[] args) {/** 不是创建 Date，* 我直接在这里使用 Instant 并解析了你的示例字符串，* 所以只需使用你的 deliveryDate.toInstant()*/String input = "2020-10-07T03:10:00Z";Instant instant = Instant.parse(input);// 然后取一个要设置的时间String timeOfDayUpdate = "07:20 AM";Instant adjusted = adjustTimeOfDay(instant, timeOfDayUpdate);System.out.println(input + " ==> " + OffsetDateTime.ofInstant(adjusted, ZoneOffset.UTC).format(DateTimeFormatter.ISO_INSTANT));}
它产生了以下输出：
2020-10-07T03:10:00Z ==> 2020-10-07T07:20:00Z
EDIT
你可以将该方法重写为：
public static Date adjustTimeOfDay(Date date, String timeOfDay) {// 将日期转换为 instant，然后将 instant 转换为带有偏移的日期时间对象OffsetDateTime deliveryOdt = OffsetDateTime.ofInstant(date.toInstant(), ZoneOffset.UTC);// 提供一个解析时间字符串的格式化器DateTimeFormatter dtf = new DateTimeFormatterBuilder().appendPattern("hh").appendLiteral(':').appendPattern("mm").appendLiteral(' ').appendPattern("a").parseCaseInsensitive().toFormatter();// 将该字符串解析为 LocalTimeLocalTime localTime = LocalTime.parse(timeOfDay, dtf);/** 创建一个新的 OffsetDateTime，* 将新的 LocalTime 添加到旧的 UTC 日期上*/OffsetDateTime adjustedOdt = OffsetDateTime.of(deliveryOdt.toLocalDate(),localTime,ZoneOffset.UTC);// 从 OffsetDateTime 获取的 Instant 返回一个 Datereturn Date.from(adjustedOdt.toInstant());}
传入一个 Date，并返回一个日期。
英文:
You can use the compatibility method java.util.Date.toInstant(), manipulate the time of day of that Instant which creates a different Instant and then convert back to a Date by Date.from(Instant instant).
Here's an example method for the manipulation:
public static Instant adjustTimeOfDay(Instant instant, String timeOfDay) {// convert the instant to an offset-aware datetime objectOffsetDateTime deliveryOdt = OffsetDateTime.ofInstant(instant, ZoneOffset.UTC);/** provide a formatter that parses a time-of-day String.* PLEASE NOT that this formatter is not very lenient,* the String must be of the pattern "hh:mm a"*/DateTimeFormatter dtf = new DateTimeFormatterBuilder().appendPattern("hh").appendLiteral(':').appendPattern("mm").appendLiteral(' ').appendPattern("a").parseCaseInsensitive().toFormatter();// parse that String to a LocalTimeLocalTime localTime = LocalTime.parse(timeOfDay, dtf);/** create a new OffsetDateTime* adding the new LocalTime to the old LocalDate at UTC*/OffsetDateTime adjustedOdt = OffsetDateTime.of(deliveryOdt.toLocalDate(),localTime,ZoneOffset.UTC);return adjustedOdt.toInstant();}
I used in a main like this:
public static void main(String[] args) {/** instead of creating a Date,* I directly use Instant here and parse your example String,* so just use your deliveryDate.toInstant()*/String input = "2020-10-07T03:10:00Z";Instant instant = Instant.parse(input);// then take a time of day to be setString timeOfDayUpdate = "07:20 AM";Instant adjusted = adjustTimeOfDay(instant, timeOfDayUpdate);System.out.println(input + " ==> " + OffsetDateTime.ofInstant(adjusted, ZoneOffset.UTC).format(DateTimeFormatter.ISO_INSTANT));}
which created the following output:
2020-10-07T03:10:00Z ==> 2020-10-07T07:20:00Z
EDIT
You can rewrite that method to
public static Date adjustTimeOfDay(Date date, String timeOfDay) {// convert the date to an instant and the instant to an offset-aware datetime objectOffsetDateTime deliveryOdt = OffsetDateTime.ofInstant(date.toInstant(), ZoneOffset.UTC);// provide a formatter that parses a time-of-day StringDateTimeFormatter dtf = new DateTimeFormatterBuilder().appendPattern("hh").appendLiteral(':').appendPattern("mm").appendLiteral(' ').appendPattern("a").parseCaseInsensitive().toFormatter();// parse that String to a LocalTimeLocalTime localTime = LocalTime.parse(timeOfDay, dtf);/** create a new OffsetDateTime* adding the new LocalTime to the old LocalDate at UTC*/OffsetDateTime adjustedOdt = OffsetDateTime.of(deliveryOdt.toLocalDate(),localTime,ZoneOffset.UTC);// return a Date from the Instant you get out of the OffsetDateTimereturn Date.from(adjustedOdt.toInstant());}
passing a Date and getting one returned.
答案2
得分: 2
如果我正确理解您的要求，您正在寻找类似以下的内容：import java.time.LocalTime;import java.time.ZoneId;import java.time.ZoneOffset;import java.time.ZonedDateTime;import java.time.format.DateTimeFormatter;import java.time.format.DateTimeFormatterBuilder;import java.util.Locale;public class Main {public static void main(String[] args) {// 测试System.out.println(adjustTimeOfDay("2020-10-07T03:10:00Z", "7:20 AM"));}public static String adjustTimeOfDay(String deliveryDate, String timeOfDay) {// 定义解析时间为 7:20 AM 的格式化器DateTimeFormatter timeFormatter = new DateTimeFormatterBuilder().parseCaseInsensitive().appendPattern("h:m a").toFormatter(Locale.ENGLISH);return ZonedDateTime.parse(deliveryDate).toLocalDate().atTime(LocalTime.parse(timeOfDay, timeFormatter)).atZone(ZoneId.of("Asia/Kuala_Lumpur")).withZoneSameInstant(ZoneOffset.UTC).format(DateTimeFormatter.ofPattern("uuuu-MM-dd'T'HH:mm:ss")) + 'Z';}}**输出:**2020-10-06T23:20:00Z我建议您在24小时制中使用`HH`。然而，如果您想要忽略`AM/PM`并获得时间字符串，您可以在上述模式中使用`hh`，然后您将获得`2020-10-06T11:20:00Z`（但我不建议这样做，因为这会令人困惑）。
英文:
If I understood your requirement correctly, you are looking for something like:
import java.time.LocalTime;import java.time.ZoneId;import java.time.ZoneOffset;import java.time.ZonedDateTime;import java.time.format.DateTimeFormatter;import java.time.format.DateTimeFormatterBuilder;import java.util.Locale;public class Main {public static void main(String[] args) {// TestSystem.out.println(adjustTimeOfDay("2020-10-07T03:10:00Z", "7:20 AM"));}public static String adjustTimeOfDay(String deliveryDate, String timeOfDay) {// Define the formatter to parse time like 7:20 AMDateTimeFormatter timeFormatter = new DateTimeFormatterBuilder().parseCaseInsensitive().appendPattern("h:m a").toFormatter(Locale.ENGLISH);return ZonedDateTime.parse(deliveryDate).toLocalDate().atTime(LocalTime.parse(timeOfDay, timeFormatter)).atZone(ZoneId.of("Asia/Kuala_Lumpur")).withZoneSameInstant(ZoneOffset.UTC).format(DateTimeFormatter.ofPattern("uuuu-MM-dd'T'HH:mm:ss")) + 'Z';}}
Output:
2020-10-06T23:20:00Z
I recommend you use use HH for a time in 24-hour format. However, if you want to get a time string by ignoring AM/PM, you can use hh in the pattern given above and then you will get 2020-10-06T11:20:00Z (but I do not recommend it as it will be confusing for anyone).
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