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().

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);

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/

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" );

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

Better yet, use JodaTime. Much easier to parse strings and into strings. Is thread safe as well. Worth the time it will take you to implement it.

To convert seconds time stamp to millisecond time stamp. You could use the TimeUnit API and neat like this.

long milliSecondTimeStamp = MILLISECONDS.convert(secondsTimeStamp, SECONDS)

Hum.... if I am not mistaken, the UNIX Epoch time is actually the same thing as

System.currentTimeMillis()

So writing

try {
    Date expiry = new Date(Long.parseLong(date));
}
catch(NumberFormatException e) {
    // ...
}

should work (and be much faster that date parsing)