Java 时间戳-如何创建日期为23/09/2007的时间戳？

如何创建日期为23/09/2007的时间戳？

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最佳答案

By Timestamp, I presume you mean java.sql.Timestamp. You will notice that this class has a constructor that accepts a long argument. You can parse this using the DateFormat class:

DateFormat dateFormat = new SimpleDateFormat("dd/MM/yyyy");
Date date = dateFormat.parse("23/09/2007");
long time = date.getTime();
new Timestamp(time);
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According to the API the constructor which would accept year, month, and so on is deprecated. Instead you should use the Constructor which accepts a long. You could use a Calendar implementation to construct the date you want and access the time-representation as a long, for example with the getTimeInMillis method.

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What do you mean timestamp? If you mean milliseconds since the Unix epoch:

GregorianCalendar cal = new GregorianCalendar(2007, 9 - 1, 23);
long millis = cal.getTimeInMillis();

If you want an actual java.sql.Timestamp object:

Timestamp ts = new Timestamp(millis);
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What about this?

java.sql.Timestamp timestamp = java.sql.Timestamp.valueOf("2007-09-23 10:10:10.0");
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You could also do the following:

// untested
Calendar cal = GregorianCalendar.getInstance();
cal.set(Calendar.DAY_OF_MONTH, 23);// I might have the wrong Calendar constant...
cal.set(Calendar.MONTH, 8);// -1 as month is zero-based
cal.set(Calendar.YEAR, 2009);
Timestamp tstamp = new Timestamp(cal.getTimeInMillis());
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A more general answer would be to import java.util.Date, then when you need to set a timestamp equal to the current date, simply set it equal to new Date().

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For completeness sake, also a solution with Joda-Time version 2.5 and its DateTime class:

new Timestamp(new DateTime(2007, 9, 23, 0, 0, DateTimeZone.forID( "America/Montreal" )).getMillis())
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tl;dr

java.sql.Timestamp.from (
LocalDate.of ( 2007 , 9 , 23 )
.atStartOfDay( ZoneId.of ( "America/Montreal" ) )
.toInstant()
)

java.time

Let’s update this page by showing code using the java.time framework built into Java 8 and later.

These new classes are inspired by Joda-Time, defined by JSR 310, and extended by the ThreeTen-Extra project. They supplant the notoriously troublesome old date-time classes bundled with early versions of Java.

In java.time, an Instant is a moment on the timeline in UTC. A ZonedDateTime is an Instant adjusted into a time zone (ZoneId).

Time zone is crucial here. A date of September 23, 2007 cannot be translated to a moment on the timeline without applying a time zone. Consider that a new day dawns earlier in Paris than in Montréal where it is still “yesterday”.

Also, a java.sql.Timestamp represents both a date and time-of-day. So we must inject a time-of-day to go along with the date. We assume you want the first moment of the day as the time-of-day. Note that this is not always the time 00:00:00.0 because of Daylight Saving Time and possibly other anomalies.

Note that unlike the old java.util.Date class, and unlike Joda-Time, the java.time types have a resolution of nanoseconds rather than milliseconds. This matches the resolution of java.sql.Timestamp.

Note that the java.sql.Timestamp has a nasty habit of implicitly applying your JVM’s current default time zone to its date-time value when generating a string representation via its toString method. Here you see my America/Los_Angeles time zone applied. In contrast, the java.time classes are more sane, using standard ISO 8601 formats.

LocalDate d = LocalDate.of ( 2007 , 9 , 23 ) ;
ZoneId z = ZoneId.of ( "America/Montreal" ) ;
ZonedDateTime zdt = d.atStartOfDay( z ) ;
Instant instant = zdt.toInstant() ;
java.sql.Timestamp ts = java.sql.Timestamp.from ( instant ) ;

Dump to console.

System.out.println ( "d: " + d + " = zdt: " + zdt + " = instant: " + instant + " = ts: " + ts );

When run.

d: 2007-09-23 = zdt: 2007-09-23T00:00-04:00[America/Montreal] = instant: 2007-09-23T04:00:00Z = ts: 2007-09-22 21:00:00.0

By the way, as of JDBC 4.2, you can use the java.time types directly. No need for java.sql.Timestamp.

  • PreparedStatement.setObject
  • ResultSet.getObject

About java.time

The java.time framework is built into Java 8 and later. These classes supplant the troublesome old legacy date-time classes such as java.util.Date, Calendar, & SimpleDateFormat.

The Joda-Time project, now in maintenance mode, advises migration to the java.time classes.

To learn more, see the Oracle Tutorial. And search Stack Overflow for many examples and explanations. Specification is JSR 310.

You may exchange java.time objects directly with your database. Use a JDBC driver compliant with JDBC 4.2 or later. No need for strings, no need for java.sql.* classes.

Where to obtain the java.time classes?

The ThreeTen-Extra project extends java.time with additional classes. This project is a proving ground for possible future additions to java.time. You may find some useful classes here such as Interval, YearWeek, YearQuarter, and more.


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