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How to convert TimeStamp to Date in Java?

由 喜欢而已 提交于 2020-01-08 15:39:54

问题


How do I convert 'timeStamp' to date after I get the count in java?

My current code is as follows:

public class GetCurrentDateTime {

    public int data() {
        int count = 0;
        java.sql.Timestamp timeStamp = new Timestamp(System.currentTimeMillis());
        java.sql.Date date = new java.sql.Date(timeStamp.getTime()); 
        System.out.println(date);
        //count++;

        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/pro", "root", "");

            PreparedStatement statement = con.prepareStatement("select * from orders where status='Q' AND date=CURDATE()");
            ResultSet result = statement.executeQuery();
            while (result.next()) {
                // Do something with the row returned.
                count++; //if the first col is a count.
            }
        } catch (Exception exc) {
            System.out.println(exc.getMessage());
        }

        return count;
    }
}

This is my database:

Here the output I got was 2012-08-07 0, but the equivalent query returns 3. Why do I get 0?


回答1:


Just make a new Date object with the stamp's getTime() value as a parameter.

Here's an example (I use an example timestamp of the current time):

Timestamp stamp = new Timestamp(System.currentTimeMillis());
Date date = new Date(stamp.getTime());
System.out.println(date);



回答2:


// timestamp to Date
long timestamp = 5607059900000; //Example -> in ms
Date d = new Date(timestamp );

// Date to timestamp
long timestamp = d.getTime();

//If you want the current timestamp :
Calendar c = Calendar.getInstance();
long timestamp = c.getTimeInMillis();



回答3:


Just:

Timestamp timestamp = new Timestamp(long);
Date date = new Date(timestamp.getTime());



回答4:


tl;dr

LocalDate.now( ZoneId.of( "Africa/Tunis" ) )
    .atStartOfDay( ZoneId.of( "Africa/Tunis" ) )
    .toEpochSecond()

…

LocalDate.now( ZoneId.of( "Africa/Tunis" ) )
    .plusDays( 1 )
    .atStartOfDay( ZoneId.of( "Africa/Tunis" ) )
    .toEpochSecond()

…

"SELECT * FROM orders WHERE placed >= ? AND placed < ? ; "

…

myPreparedStatement.setObject( 1 , start )
myPreparedStatement.setObject( 2 , stop )

java.time

You are using troublesome old date-time classes that are now legacy, supplanted by the modern java.time classes.

Apparently you are storing a moment in your database in a column of some integer type. That is unfortunate. You should instead be using a column of a type such as the SQL-standard TIMESTAMP WITH TIME ZONE. But, for this Answer, we will work with what we have.

If your records represent moments with a resolution of milliseconds, and you want all the records for an entire day, then we need a time range. We must have a start moment and a stop moment. Your query has only a single date-time criterion where it should have had a pair.

The LocalDate class represents a date-only value without time-of-day and without time zone.

A time zone is crucial in determining a date. For any given moment, the date varies around the globe by zone. For example, a few minutes after midnight in Paris France is a new day while still “yesterday” in Montréal Québec.

If no time zone is specified, the JVM implicitly applies its current default time zone. That default may change at any moment, so your results may vary. Better to specify your desired/expected time zone explicitly as an argument.

Specify a proper time zone name in the format of continent/region, such as America/Montreal, Africa/Casablanca, or Pacific/Auckland. Never use the 3-4 letter abbreviation such as EST or IST as they are not true time zones, not standardized, and not even unique(!). 

ZoneId z = ZoneId.of( "America/Montreal" ) ;  
LocalDate today = LocalDate.now( z ) ;

If you want to use the JVM’s current default time zone, ask for it and pass as an argument. If omitted, the JVM’s current default is applied implicitly. Better to be explicit, as the default may be changed at any moment during runtime by any code in any thread of any app within the JVM.

ZoneId z = ZoneId.systemDefault() ;  // Get JVM’s current default time zone.

Or specify a date. You may set the month by a number, with sane numbering 1-12 for January-December. 

LocalDate ld = LocalDate.of( 1986 , 2 , 23 ) ;  // Years use sane direct numbering (1986 means year 1986). Months use sane numbering, 1-12 for January-December.

Or, better, use the Month enum objects pre-defined, one for each month of the year. Tip: Use these Month objects throughout your codebase rather than a mere integer number to make your code more self-documenting, ensure valid values, and provide type-safety.

LocalDate ld = LocalDate.of( 1986 , Month.FEBRUARY , 23 ) ;

With a LocalDate in hand, we next need to transform that into a pair of moment, the start and stop of the day. Do not assume the day starts at 00:00:00 time-of-day. Because of anomalies such as Daylight Saving Time (DST), the day may start at another time such as 01:00:00. So let java.time determine the first moment of the day. We pass a ZoneId argument to LocalDate::atStartOfDay to look up any such anomalies. The result is a ZonedDateTime.

ZonedDateTime zdtStart = ld.atStartOfDay( z ) ;

Generally the best approach to defining a span of time is the Half-Open approach where the beginning is inclusive while the ending is exclusive. So a day starts with its first moment and runs up to, but not including, the first moment of the next day.

ZonedDateTime zdtStop = ld.plusDays( 1 ).atStartOfDay( z ) ;  // Determine the following date, and ask for the first moment of that day.

Our query for an entire day cannot make use of SQL command BETWEEN. That command is Fully-Closed ([]) (both beginning and ending are inclusive) where as we want Half-Open ([)). We use a pair of criteria >= and <.

Your column is poorly named. Avoid any of the thousand words reserved by various databases. Let’s use placed in this example.

Your code should have used ? placeholders in which to specify our moments.

String sql = "SELECT * FROM orders WHERE placed >= ? AND placed < ? ; " ;

But we have ZonedDateTime objects in hand, while your database apparently is storing integers as discussed above. If you had defined your column properly we could simply pass the ZonedDateTime objects with any JDBC driver supporting JDBC 4.2 or later.

But instead we need to get a count-from-epoch in whole seconds. I will assume your epoch reference date is the first moment of 1970 in UTC. Beware of possible data loss, as the ZonedDateTime class is capable of nanosecond resolution. Any fractional second will be truncated in the following lines.

long start = zdtStart().toEpochSecond() ;  // Transform to a count of whole seconds since 1970-01-01T00:00:00Z.
long stop = zdtStop().toEpochSecond() ;

Now we are ready to pass those integers to our SQL code defined above.

PreparedStatement ps = con.prepareStatement( sql );
ps.setObject( 1 , start ) ;
ps.setObject( 2 , stop ) ;
ResultSet rs = ps.executeQuery();

When you retrieve your integer values from the ResultSet, you can transform into Instant objects (always in UTC), or into ZonedDateTime objects (with an assigned time zone).

Instant instant = rs.getObject( … , Instant.class ) ;
ZonedDateTime zdt = instant.atZone( z ) ;

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.

Where to obtain the java.time classes?

  • Java SE 8, Java SE 9, and later
    • Built-in.
    • Part of the standard Java API with a bundled implementation.
    • Java 9 adds some minor features and fixes.
  • Java SE 6 and Java SE 7
    • Much of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
  • Android
    • Later versions of Android bundle implementations of the java.time classes.
    • For earlier Android, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above). See How to use ThreeTenABP….

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.




回答5:


I have been looking for this since a long time, turns out that Eposh converter does it easily:

long epoch = new java.text.SimpleDateFormat("MM/dd/yyyy HH:mm:ss").parse("01/01/1970 01:00:00").getTime() / 1000;

Or the opposite: 

String date = new java.text.SimpleDateFormat("MM/dd/yyyy HH:mm:ss").format(new java.util.Date (epoch*1000));



回答6:


First of all, you're not leveraging the advantage of using a PreparedStatement. I would first suggest that you modify your PreparedStatement as follows:

PreparedStatement statement = con.prepareStatement("select * from orders where status=? AND date=?")

You can then use statement.setXX(param_index, param_value) to set the respective values. For conversion to timestamp, have a look at the following javadocs:

PreparedStatement.setTimeStamp()
Timestamp

Hope this helps!




回答7:


Not sure what you're trying to select in the query, but keep in mind that UNIX_TIMESTAMP() without arguments returns the time now. You should probably provide a valid time as argument, or change the condition.

EDIT:

Here is an example of a time bound query based on the question: 

PreparedStatement statement = con
        .prepareStatement("select * from orders where status='Q' AND date > ?");
Date date = new SimpleDateFormat("dd/MM/yyyy").parse("01/01/2000");
statement.setDate(1, new java.sql.Date(date.getTime()));

EDIT: timestamp column

In case of timestamp use java.sql.Timestamp and PreparedStatement.setTimestamp(), ie: 

PreparedStatement statement = con
        .prepareStatement("select * from orders where status='Q' AND date > ?");
Date date = new SimpleDateFormat("dd/MM/yyyy").parse("01/01/2000");
Timestamp timestamp = new Timestamp(date.getTime());
statement.setTimestamp(1, timestamp);



回答8:


new Date(timestamp.getTime()) should work, but the new fancy Java 8 way (which may be more elegant and more type safe, as well as help lead you to use the new time classes) is to call Date.from(timestamp.toInstant()).

(Do not rely on the fact that Timestamp itself is an instance of Date; see explanation in the comments of another answer .)




回答9:


    Timestamp tsp = new Timestamp(System.currentTimeMillis());
   java.util.Date dateformat = new java.util.Date(tsp.getTime());



回答10:


In Android its very Simple .Just use the Calender class to get currentTimeMillis.

Timestamp stamp = new Timestamp(Calendar.getInstance().getTimeInMillis());
Date date = new Date(stamp.getTime());
Log.d("Current date Time is   "  +date.toString());

In Java just Use System.currentTimeMillis() to get current timestamp




回答11:


I feel obliged to respond since other answers seem to be time zone agnostic which a real world application cannot afford to be. To make timestamp-to-date conversion correct when the timestamp and the JVM are using different time zones you can use Joda Time's LocalDateTime (or LocalDateTime in Java8) like this:

Timestamp timestamp = resultSet.getTimestamp("time_column");
LocalDateTime localDateTime = new LocalDateTime(timestamp);
Date trueDate = localDateTime.toDate(DateTimeZone.UTC.toTimeZone());

The example below assumes that the timestamp is UTC (as is usually the case with databases). In case your timestamps are in different timezone, change the timezone parameter of the toDatestatement.




回答12:


Assuming you have a pre-existing java.util.Date date:

Timestamp timestamp = new Timestamp(long);
date.setTime( l_timestamp.getTime() );



回答13:


You can use this method to get Date from Timestamp and Time-zone of particular area.

public String getDayOfTimestamp(long yourLinuxTimestamp, String timeZone) {
    Calendar cal = Calendar.getInstance();
    cal.setTimeInMillis(yourLinuxTimestamp * 1000);
    cal.setTimeZone(TimeZone.getTimeZone(timeZone));
    Date date = cal.getTime();
}



回答14:


try to use this java code :

Timestamp stamp = new Timestamp(System.currentTimeMillis());
Date date = new Date(stamp.getTime());
DateFormat f = new SimpleDateFormat("yyyy-MM-dd");
DateFormat f1 = new SimpleDateFormat("yyyy/MM/dd");
String d = f.format(date);
String d1 = f1.format(date);
System.out.println(d);
System.out.println(d1);



回答15:


String timestamp="";
Date temp=null;
try {
    temp = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").parse(getDateCurrentTimeZone(Long.parseLong(timestamp)));
} catch (ParseException e) {
    // TODO Auto-generated catch block
    e.printStackTrace();
}
int dayMonth=temp.getDate();
int dayWeek=temp.getDay();
int hour=temp.getHours();
int minute=temp.getMinutes();
int month=temp.getMonth()+1;
int year=temp.getYear()+1900;



回答16:


DateFormat df = new SimpleDateFormat("dd/MM/yyyy");
Date fecha = getDateInTimestamp();


来源：https://stackoverflow.com/questions/11839246/how-to-convert-timestamp-to-date-in-java

标签
java
date
jdbc
timestamp
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