How do I say 5 seconds from now in Java?

Question

I am looking at the Date documentation and trying to figure out how I can express NOW + 5 seconds. Here\'s some pseudocode:

import java.util.Date
public clas         


        

Answer 1

I just found this from java docs

import java.util.Calendar;

public class Main {

  public static void main(String[] args) {
    Calendar now = Calendar.getInstance();
    System.out.println("Current time : " + now.get(Calendar.HOUR_OF_DAY) + ":"
        + now.get(Calendar.MINUTE) + ":" + now.get(Calendar.SECOND));

    now.add(Calendar.SECOND, 100);
    System.out.println("New time after adding 100 seconds : " + now.get(Calendar.HOUR_OF_DAY) + ":"
        + now.get(Calendar.MINUTE) + ":" + now.get(Calendar.SECOND));
  }
}

Is there a convention I should be aware of?

Answer 2

UPDATE: See my new Answer using java.time classes. I am leaving this Answer intact as history.

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The Answer by Pascal Thivent and the Answer by Jon Skeet are both correct and good. Here's a bit of extra info.

Five Seconds = PT5S (ISO 8601)

Another way to express the idea of "five seconds later" is in a string using the standard formats defined by ISO 8601. The duration/period format has this pattern PnYnMnDTnHnMnS where the P marks the beginning and the T separates the date portion from time portion.

So five seconds is PT5S.

Joda-Time

The Joda-Time 2.8 library can both generate and parse such duration/period strings. See the Period, Duration, and Interval classes. You can add and subtract Period objects to/from DateTime objects.

Search StackOverflow for many examples and discussions. Here's one quick example.

DateTimeZone zone = DateTimeZone.forID( "America/Montreal" );
DateTime now = DateTime.now( zone );
DateTime then = now.plusSeconds( 5 );
Interval interval = new Interval( now, then );
Period period = interval.toPeriod( );

DateTime thenAgain = now.plus( period );

Dump to console.

System.out.println( "zone: " + zone );
System.out.println( "From now: " + now + " to then: " + then );
System.out.println( "interval: " + interval );
System.out.println( "period: " + period );
System.out.println( "thenAgain: " + thenAgain );

When run.

zone: America/Montreal
From now: 2015-06-15T19:38:21.242-04:00 to then: 2015-06-15T19:38:26.242-04:00
interval: 2015-06-15T19:38:21.242-04:00/2015-06-15T19:38:26.242-04:00
period: PT5S
thenAgain: 2015-06-15T19:38:26.242-04:00

Answer 3

Date is almost entirely deprecated and is still there for backward compatibility reasons. If you need to set particular dates or do date arithmetic, use a Calendar:

Calendar calendar = Calendar.getInstance(); // gets a calendar using the default time zone and locale.
calendar.add(Calendar.SECOND, 5);
System.out.println(calendar.getTime());

Answer 4

Try This..

    Date now = new Date();
    System.out.println(now);

    Calendar c = Calendar.getInstance();
    c.setTime(now);
    c.add(Calendar.SECOND, 5);
    now = c.getTime();

    System.out.println(now);

    // Output
    Tue Jun 11 16:46:43 BDT 2019
    Tue Jun 11 16:46:48 BDT 2019

Answer 5

As others have pointed out, in Joda it's much easier:

DateTime dt = new DateTime();
DateTime added = dt.plusSeconds(5);

I would strongly recommend you migrate to Joda. Almost any Java date-related question on SO resolves to a Joda recommendation :-) The Joda API is supposed to be the basis of the new standard Java date API (JSR310), so you'll be migrating towards a new standard.