如何在Java中将日期和SQL时间组合成单个日期时间？

huangapple
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英文:

how can you combine date and sql time into a single date time in java?

问题

使用Java Calendar，您可以如何将开始日期、天数和开始时间组合在一起？

例如：

如果开始日期是9/8/2020，天数是2，开始时间是8:00 AM，那么我们如何获得一个Java日期，即9/9/2020 8:00 AM？以下是我的尝试：

  1. import java.util.Calendar;
  2. import java.util.Date;
  4. public Date startDateTime(Date startDate, int day, java.sql.Time startTime) {    
  6.     Calendar date = Calendar.getInstance();
  7.     date.setTime(startDate);
  9.     // 添加天数。由于第1天是第一天，我们需要添加day - 1
  10.     date.add(Calendar.DATE, day - 1);
  11.     
  12.     // 设置时间为startTime的时间
  13.     Calendar time = Calendar.getInstance();
  14.     time.setTimeInMillis(startTime.getTime());
  15.     
  16.     date.set(Calendar.HOUR_OF_DAY, time.get(Calendar.HOUR_OF_DAY));
  17.     date.set(Calendar.MINUTE, time.get(Calendar.MINUTE));
  18.     date.set(Calendar.SECOND, time.get(Calendar.SECOND));
  20.     return date.getTime();
  21. }

谢谢您的帮助。

英文:

Using java Calendar how can you combine the start date, day and starttime?

For example:

If the start date is 9/8/2020. The day is 2 and the start time is 8:00 AM then how can we obtain a java date that is 9/9/2020 8:00 AM. Here is my unsuccessful attempt.

  1. def startDateTime(Date startDate, int day, java.sql.Time startTime){    
  3. 		def date
  4. 		date = Calendar.getInstance()
  5. 		date.setTime(startDate)
  7.         //adding day. since day 1 is the first day we need to add day - 1
  8. 		date.add(Calendar.DATE, day - 1)   
  9.         // setting the time from startTime
  10. 		date.setTimeInMillis(startTime.getTime())
  11.     
  12. 		return date.getTime()
  14. 	}

Thanks for the help.

答案1

得分: 1

你正在调用date.setTime(startDate)和date.setTimeInMillis(startTime.getTime())。第二个方法会覆盖第一个方法设置的时间。你应该创建两个单独的Calendar实例。

以下是如何实现这一点：

  1. 为startDay和startTime创建单独的Calendar实例。
  2. 根据需要从在步骤1中创建的单独的Calendar对象构造一个新的Calendar对象，并添加day。

以下是完整的代码：

  1. import java.sql.Time;
  2. import java.time.LocalDateTime;
  3. import java.time.ZoneId;
  4. import java.util.Calendar;
  5. import java.util.Date;
  7. public class ProofOfConcept {
  9.     public static void main(String[] args) {
  10.         int day = 2;
  12.         Time startTime = new Time(1, 1, 1);
  13.         Calendar timeCalendar = Calendar.getInstance();
  14.         timeCalendar.setTime(startTime);
  16.         Date startDate = new Date();
  17.         Calendar startDateCalendar = Calendar.getInstance();
  18.         startDateCalendar.setTime(startDate);
  20.         Calendar result = Calendar.getInstance();
  21.         result.set(startDateCalendar.get(Calendar.YEAR), startDateCalendar.get(Calendar.MONTH), startDateCalendar.get(Calendar.DAY_OF_MONTH) + 2,
  22.                 timeCalendar.get(Calendar.HOUR), timeCalendar.get(Calendar.MINUTE), timeCalendar.get(Calendar.SECOND));
  24.         Date date = result.getTime();
  25.         System.out.println("date : " + date);
  26.     }
  27. }

输出：

date : Tue Sep 08 01:01:01 IST 2020

注意：我建议在java.util.*之上使用java.time.*包。为什么？请查看这里。但这仅适用于Java 8及以上。（尽管在8以下版本中可以使用joda time）。

编辑：将Ole V.V.的评论移到答案中。

对于Java 7，我建议通过后移ThreeTen Backport来使用现代Java日期和时间API，即java.time。

  1. static LocalDateTime startDateTime(Date startDate, int day, java.sql.Time startTime) {
  2.     LocalTime startLocalTime = DateTimeUtils.toLocalTime(startTime);
  3.     return DateTimeUtils.toInstant(startDate)
  4.             .atZone(ZoneId.systemDefault())
  5.             .toLocalDate()
  6.             .plusDays(day - 1)
  7.             .atTime(startLocalTime);
  8. }
英文:

You are calling date.setTime(startDate) and date.setTimeInMillis(startTime.getTime()). 2nd method is overriding the time set in 1st method. You should create 2 separate instances of Calendar.

Here is how you can achieve this

  1. Create separate Calendar instances for startDay and startTime
  2. Construct a new Calendar object from separate Calendar objects created in #1 & add day as per requirement

Here is the complete code:

  1. import java.sql.Time;
  2. import java.time.LocalDateTime;
  3. import java.time.ZoneId;
  4. import java.util.Calendar;
  5. import java.util.Date;
  7. public class ProofOfConcept {
  9.     public static void main(String[] args) {
  10.         int day = 2;
  12.         Time startTime = new Time(1, 1, 1);
  13.         Calendar timeCalendar = Calendar.getInstance();
  14.         timeCalendar.setTime(startTime);
  16.         Date startDate = new Date();
  17.         Calendar startDateCalendar = Calendar.getInstance();
  18.         startDateCalendar.setTime(startDate);
  20.         /* Only java 8 and above
  21.         LocalDateTime localDateTime = LocalDateTime.of(startDateCalendar.get(Calendar.YEAR), startDateCalendar.get(Calendar.MONTH) + 1, startDateCalendar.get(Calendar.DAY_OF_MONTH),
  22.                 timeCalendar.get(Calendar.HOUR), timeCalendar.get(Calendar.MINUTE), timeCalendar.get(Calendar.SECOND));
  23.         localDateTime = localDateTime.plusDays(day);
  24.         System.out.println("localDateTime : " + localDateTime);
  25.         Date dateFromLocalDateTime = Date.from(localDateTime.atZone(ZoneId.systemDefault()).toInstant());
  26.         System.out.println("dateFromLocalDateTime : " + dateFromLocalDateTime);*/
  28.         Calendar result = Calendar.getInstance();
  29.         result.set(startDateCalendar.get(Calendar.YEAR), startDateCalendar.get(Calendar.MONTH), startDateCalendar.get(Calendar.DAY_OF_MONTH) + 2,
  30.                 timeCalendar.get(Calendar.HOUR), timeCalendar.get(Calendar.MINUTE), timeCalendar.get(Calendar.SECOND));
  32.         Date date = result.getTime();
  33.         System.out.println("date : " + date);
  34.     }
  36. }

Output:
> date : Tue Sep 08 01:01:01 IST 2020

Note : I suggest using java.time.* packages over java.util.*. Why? Check this. But this is only available in java 8. (Though, you can use joda time in versions below 8).

Edit : Moving Ole V.V. 's comment to answer.

For Java 7, I suggest using java.time, the modern Java date and time API, through the backport, ThreeTen Backport.

  1. static LocalDateTime startDateTime(Date startDate, int day, java.sql.Time startTime) {
  2. 	LocalTime startLocalTime = DateTimeUtils.toLocalTime(startTime);
  3. 	return DateTimeUtils.toInstant(startDate)
  4. 			.atZone(ZoneId.systemDefault())
  5. 			.toLocalDate()
  6. 			.plusDays(day - 1)
  7. 			.atTime(startLocalTime);
  8. }

huangapple
  • 本文由 发表于 2020年9月6日 13:08:29
  • 转载请务必保留本文链接：https://go.coder-hub.com/63760901.html
  • java
  • java-7
  • java-calendar
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