Unix epoch time to Java Date object

I have a string containing the UNIX Epoch time, and I need to convert it to a Java Date object.

String date = "1081157732";
DateFormat df = new SimpleDateFormat(""); // This line
try {
  Date expiry = df.parse(date);
 } catch (ParseException ex) {
  ex.getStackTrace();
}

The marked line is where I'm having trouble. I can't work out what the argument to SimpleDateFormat() should be, or even if I should be using SimpleDateFormat().

Solution 1:

How about just:

Date expiry = new Date(Long.parseLong(date));

EDIT: as per rde6173's answer and taking a closer look at the input specified in the question , "1081157732" appears to be a seconds-based epoch value so you'd want to multiply the long from parseLong() by 1000 to convert to milliseconds, which is what Java's Date constructor uses, so:

Date expiry = new Date(Long.parseLong(date) * 1000);

Solution 2:

Epoch is the number of seconds since Jan 1, 1970..

So:

String epochString = "1081157732";
long epoch = Long.parseLong( epochString );
Date expiry = new Date( epoch * 1000 );

For more information: http://www.epochconverter.com/

Solution 3:

java.time

Using the java.time framework built into Java 8 and later.

import java.time.LocalDateTime;
import java.time.Instant;
import java.time.ZoneId;

long epoch = Long.parseLong("1081157732");
Instant instant = Instant.ofEpochSecond(epoch);
ZonedDateTime.ofInstant(instant, ZoneOffset.UTC); # ZonedDateTime = 2004-04-05T09:35:32Z[UTC]

In this case you should better use ZonedDateTime to mark it as date in UTC time zone because Epoch is defined in UTC in Unix time used by Java.

ZoneOffset contains a handy constant for the UTC time zone, as seen in last line above. Its superclass, ZoneId can be used to adjust into other time zones.

ZoneId zoneId = ZoneId.of( "America/Montreal" );

Solution 4:

long timestamp = Long.parseLong(date)
Date expiry = new Date(timestamp * 1000)