long timestamp to LocalDateTime

If you are using the Android threeten back port then the line you want is this

LocalDateTime.ofInstant(Instant.ofEpochMilli(startTime), ZoneId.systemDefault())

You need to pass timestamp in milliseconds:

long test_timestamp = 1499070300000L;
LocalDateTime triggerTime =
        LocalDateTime.ofInstant(Instant.ofEpochMilli(test_timestamp), 
                                TimeZone.getDefault().toZoneId());  

System.out.println(triggerTime);

Result:

2017-07-03T10:25

Or use ofEpochSecond instead:

long test_timestamp = 1499070300L;
LocalDateTime triggerTime =
       LocalDateTime.ofInstant(Instant.ofEpochSecond(test_timestamp),
                               TimeZone.getDefault().toZoneId());   

System.out.println(triggerTime);

Result:

2017-07-03T10:25

Try with Instant.ofEpochMilli() or Instant.ofEpochSecond() method with it-

long test_timestamp = 1499070300L;
LocalDateTime date =
    LocalDateTime.ofInstant(Instant.ofEpochMilli(test_timestamp ), TimeZone
        .getDefault().toZoneId());

Try with the following..

long test_timestamp = 1499070300000L;
    LocalDateTime triggerTime =
            LocalDateTime.ofInstant(Instant.ofEpochMilli(test_timestamp), TimeZone
                    .getDefault().toZoneId());  

By default 1499070300000 is int if it dosen't contain l in end.Also pass time in milliseconds.