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

tl;dr

Instant             // Use modern `java.time.Instant` class to represent a moment in UTC.
.now()              // Capture the current moment in UTC.
.plusSeconds( 5 )   // Add five seconds into the future. Returns another `Instant` object per the Immutable Objects pattern.

java.time

Use the modern java.time classes that years ago supplanted the terrible Date & Calendar classes.

UTC

To work in UTC, use Instant.

Instant later = Instant.now().plusSeconds( 5 ) ;

Time zone

To work in a specific time zone, use ZonedDateTime.

ZoneId z = ZoneId.of( "America/Montreal" ) ;
ZonedDateTime later = ZonedDateTime.now( z ).pluSeconds( 5 ) ;

Duration

You can soft-code the amount and granularity of time to add. Use the Duration class.

Duration d = Duration.ofSeconds( 5 ) ;
Instant later = Instant.now().plus( d ) ;  // Soft-code the amount of time to add or subtract.

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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.

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

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

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. Hibernate 5 & JPA 2.2 support java.time.

Where to obtain the java.time classes?

• Java SE 8, Java SE 9, Java SE 10, Java SE 11, and later - Part of the standard Java API with a bundled implementation.
  • Java 9 brought some minor features and fixes.
• Java SE 6 and Java SE 7
  • Most of the java.time functionality is back-ported to Java 6 & 7 in ThreeTen-Backport.
• Android
  • Later versions of Android (26+) bundle implementations of the java.time classes.
  • For earlier Android (<26), a process known as API desugaring brings a subset of the java.time functionality not originally built into Android.
    • If the desugaring does not offer what you need, the ThreeTenABP project adapts ThreeTen-Backport (mentioned above) to Android. See How to use ThreeTenABP….

Answer 2

From the one-liner-hacky dep.:

new Date( System.currentTimeMillis() + 5000L)

As I understand it from your example, 'now' is really 'now', and "System.currentTimeMillis()' happens to represent that same 'now' concept :-)

But, yup, for everything more complicated than that the Joda time API rocks.

Answer 3

You can use:

now.setTime(now.getTime() + 5000);

Date.getTime() and setTime() always refer to milliseconds since January 1st 1970 12am UTC.

Joda-Time

However, I would strongly advise you to use Joda Time if you're doing anything more than the very simplest of date/time handling. It's a much more capable and friendly library than the built-in support in Java.

DateTime later = DateTime.now().plusSeconds( 5 );

java.time

Joda-Time later inspired the new java.time package built into Java 8.

Answer 4

Ignoring Dates and focusing on the question.

My preference is to use java.util.concurrent.TimeUnit since it adds clarity to my code.

In Java,

long now = System.currentTimeMillis();

5 seconds from now using TimeUtil is:

long nowPlus5Seconds = now + TimeUnit.SECONDS.toMillis(5);

Reference: http://docs.oracle.com/javase/7/docs/api/java/util/concurrent/TimeUnit.html

Answer 5

public class datetime {

    public String CurrentDate() {        
        java.util.Date dt = new java.util.Date();
        java.text.SimpleDateFormat sdf = new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); 
        String currentTime = sdf.format(dt);
        return currentTime;
    }

    public static void main(String[] args) {
        class SayHello extends TimerTask {
            datetime thisObj = new datetime();
            public void run() {
                String todaysdate = thisObj.CurrentDate();
                System.out.println(todaysdate);
            }
        }
        Timer timer = new Timer();
        timer.schedule(new SayHello(), 0, 5000); 
    }
}

Answer 6

        String serverTimeSync = serverTimeFile.toString();
        SimpleDateFormat serverTime = new SimpleDateFormat("yyyy,MM,dd,HH,mm,ss");
        Calendar c = Calendar.getInstance();
        c.setTime(serverTime.parse(serverTimeSync));
        c.add(Calendar.MILLISECOND, 15000);
        serverTimeSync = serverTime.format(c.getTime());