将Java中的java.util.date默认格式转换为Timestamp

Question

The default format of java.util.date is something like this "Mon May 27 11:46:15 IST 2013". How can I convert this into timestamp and calculate in seconds the difference between the same and current time?

java.util.Date date= new java.util.Date();
Timestamp ts_now = new Timestamp(date.getTime());

The above code gives me the current timestamp. However, I got no clue how to find the timestamp of the above string.

Answer 1

You can use the Calendar class to convert Date

public long getDifference()
{
    SimpleDateFormat sdf = new SimpleDateFormat("EEE MMM dd kk:mm:ss z yyyy");
    Date d = sdf.parse("Mon May 27 11:46:15 IST 2013");

    Calendar c = Calendar.getInstance();
    c.setTime(d);
    long time = c.getTimeInMillis();
    long curr = System.currentTimeMillis();
    long diff = curr - time;    //Time difference in milliseconds
    return diff/1000;
}

Answer 2

Best one

String str_date=month+"-"+day+"-"+yr;
DateFormat formatter = new SimpleDateFormat("MM-dd-yyyy");
Date date = (Date)formatter.parse(str_date); 
long output=date.getTime()/1000L;
String str=Long.toString(output);
long timestamp = Long.parseLong(str) * 1000;

Answer 3

You can use

  long startTime = date.getTime() * 1000000;;
  long estimatedTime = System.nanoTime() - startTime;

To get time in nano.

Java Docs

Answer 4

You can use DateFormat (java.text.*) to parse the date:

DateFormat df = new SimpleDateFormat("EEE MMM dd kk:mm:ss z yyyy", Locale.ENGLISH);
Date d = df.parse("Mon May 27 11:46:15 IST 2013")

You will have to change the locale to match your own (with this you will get 10:46:15). Then you can use the same code you have to convert it to a timestamp.

Answer 5

java.time

I am providing the modern answer. The Timestamp class was always poorly designed, a real hack on top of the already poorly designed Date class. Both those classes are now long outdated. Don't use them.

When the question was asked, you would need a Timestamp for sending a point in time to the SQL database. Since JDBC 4.2 that is no longer the case. Assuming your database needs a timestamp with time zone (recommended for true timestamps), pass it an OffsetDateTime .

Before we can do that we need to overcome a real trouble with your sample string, Mon May 27 11:46:15 IST 2013 : the time zone abbreviation. IST may mean Irish Summer Time, Israel Standard Time or India Standard Time (I have even read that Java may parse it into Atlantic/Reykjavik time zone — Icelandic Standard Time?) To control the interpretation we pass our preferred time zone to the formatter that we are using for parsing.

    DateTimeFormatter formatter = new DateTimeFormatterBuilder()
            .appendPattern("EEE MMM dd HH:mm:ss ")
            .appendZoneText(TextStyle.SHORT, Set.of(ZoneId.of("Asia/Kolkata")))
            .appendPattern(" yyyy")
            .toFormatter(Locale.ROOT);
    String dateString = "Mon May 27 11:46:15 IST 2013";
    OffsetDateTime dateTime = formatter.parse(dateString, Instant::from)
            .atOffset(ZoneOffset.UTC);
    System.out.println(dateTime);

This snippet prints:

2013-05-27T06:16:15Z

This is the UTC equivalent of your string (assuming IST was for India Standard Time). Pass the OffsetDateTime to your database using one of the PreparedStatement.setObject methods (not setTimestamp ).

How can I convert this into timestamp and calculate in seconds the difference between the same and current time?

Calculating the difference in seconds goes very naturally with java.time:

    long differenceInSeconds = ChronoUnit.SECONDS
            .between(dateTime, OffsetDateTime.now(ZoneOffset.UTC));
    System.out.println(differenceInSeconds);

When running just now I got:

202213260

Link: Oracle tutorial: Date Time explaining how to use java.time.