CODEWITHSUNDEEP
javaoracle-databasehibernate
user3135880
user3135880

Reputation: 11

How to add days to date fetched from database with hibernate

i am fetching date from Oracle database using rp.getStart_date() with hibernate now i want to add 15 days to it and display it. but as cal.add() requires first argument as int,it is showing me numberFormatException on second line..how do i do it? 

                    Date dt=rp.getStart_date();
        int s1=Integer.parseInt((dt.toString()));
        System.out.println(s1);
        SimpleDateFormat sdf=new SimpleDateFormat("dd-MM-yyyy");
        Calendar cal=Calendar.getInstance();
        cal.add(s1, 15);
        System.out.println(sdf.format(cal.getTime()));

please help me out..

Thanks in advance..

Upvotes: 0

Views: 820

Answers (2)

Basil Bourque
Basil Bourque

Reputation: 338730

Neglected Time Zone

The answer by Rakesh KR is close but not quite right. Both the question and that answer fail to think about time zone. If you neglect to specify a time zone, you get the JVM's default time zone. By relying on default time zone, you may have unexpected results.

DST Effect

The add method of java.util.Calendar retains the hour-of-day, adjusting for Daylight Saving Time (DST) and possibly other anomalies. So if you use a time zone (like United States west coast) that changes Daylight Saving Time by an hour during your time span, you actually will have one extra/less hour. That is, your result in hours of adding 15 days is ( ( 15 * 24 ) ± 1 ).

If you were expecting ( 15 * 24 ) consistently, you will be surprised (depending default time zone of JVM).

Demonstration

Since the plusDays method on DateTime class in Joda-Time has the same behavior, I'll demonstrate using Joda-Time. You should be avoiding java.util.Date & java.util.Calendar anyways, but in this scenario the behavior is the same as Joda-Time.

First, for your information, the code from the other answer could be done Joda-Time like this, converting to-and-fro between the java.util.Date world and Joda-Time world. But this code has the same time zone issue (affected by DST).

java.util.Date juDate = new java.util.Date();
java.util.Date juDateLater = new DateTime( juDate ).plusDays( 15 ).toDate() ;

Now using pure Joda-Time let's look at how time zone affects the addition of days. We will run this example code twice, first as-is, then swapping time zones by commenting out the first timeZone line and enabling the line after that.

// Time zone "America/Los_Angeles" begins DST on 2014-03-09 02:00, springing ahead to 03:00.
DateTimeZone timeZone = DateTimeZone.forID( "America/Los_Angeles" );
//DateTimeZone timeZone = DateTimeZone.UTC;

DateTime dateTime_OneAM = new DateTime( 2014, 3, 9, 1, 0, 0, timeZone );
DateTime dateTime_OneAM_Plus15 = dateTime_OneAM.plusDays( 15 );

DateTime dateTime_ThreeAM = new DateTime( 2014, 3, 9, 3, 0, 0, timeZone );
DateTime dateTime_ThreeAM_Plus15 = dateTime_ThreeAM.plusDays( 15 );

long millisElapsedOneAM = ( dateTime_OneAM_Plus15.getMillis() - dateTime_OneAM.getMillis() );
long millisElapsedThreeAM = ( dateTime_ThreeAM_Plus15.getMillis() - dateTime_ThreeAM.getMillis() );
long minutes = ( ( millisElapsedThreeAM - millisElapsedOneAM ) / 1000L / 60L );

Dump to console…

System.out.println( "timeZone " + timeZone );
System.out.println( "dateTime_OneAM " + dateTime_OneAM + " ( UTC/GMT: " + dateTime_OneAM.toDateTime( DateTimeZone.UTC ) + " )" );
System.out.println( "dateTime_OneAM_Plus15 " + dateTime_OneAM_Plus15 + " ( UTC/GMT: " + dateTime_OneAM_Plus15.toDateTime( DateTimeZone.UTC ) + " )" );
System.out.println( " " ); // Blank line.
System.out.println( "dateTime_ThreeAM " + dateTime_ThreeAM + " ( UTC/GMT: " + dateTime_ThreeAM.toDateTime( DateTimeZone.UTC ) + " )" );
System.out.println( "dateTime_ThreeAM_Plus15 " + dateTime_ThreeAM_Plus15 + " ( UTC/GMT: " + dateTime_ThreeAM_Plus15.toDateTime( DateTimeZone.UTC ) + " )" );
System.out.println( " " ); // Blank line.
System.out.println( "millisElapsedOneAM " + millisElapsedOneAM );
System.out.println( "millisElapsedThreeAM " + millisElapsedThreeAM );
System.out.println( "minutes " + minutes );

When run using the first time zone, for US west coast…
(Note how hour-of-day in UTC changing or not changing)

timeZone America/Los_Angeles
dateTime_OneAM 2014-03-09T01:00:00.000-08:00 ( UTC/GMT: 2014-03-09T09:00:00.000Z )
dateTime_OneAM_Plus15 2014-03-24T01:00:00.000-07:00 ( UTC/GMT: 2014-03-24T08:00:00.000Z )

dateTime_ThreeAM 2014-03-09T03:00:00.000-07:00 ( UTC/GMT: 2014-03-09T10:00:00.000Z )
dateTime_ThreeAM_Plus15 2014-03-24T03:00:00.000-07:00 ( UTC/GMT: 2014-03-24T10:00:00.000Z )

millisElapsedOneAM 1292400000
millisElapsedThreeAM 1296000000
minutes 60

When run using the second time zone, for UTC/GMT…

timeZone UTC
dateTime_OneAM 2014-03-09T01:00:00.000Z ( UTC/GMT: 2014-03-09T01:00:00.000Z )
dateTime_OneAM_Plus15 2014-03-24T01:00:00.000Z ( UTC/GMT: 2014-03-24T01:00:00.000Z )

dateTime_ThreeAM 2014-03-09T03:00:00.000Z ( UTC/GMT: 2014-03-09T03:00:00.000Z )
dateTime_ThreeAM_Plus15 2014-03-24T03:00:00.000Z ( UTC/GMT: 2014-03-24T03:00:00.000Z )

millisElapsedOneAM 1296000000
millisElapsedThreeAM 1296000000
minutes 0

Upvotes: 0

Rakesh KR
Rakesh KR

Reputation: 6527

Try,

Date             dt  = rp.getStart_date();
SimpleDateFormat sdf = new SimpleDateFormat("dd-MM-yyyy");
Calendar         cal = Calendar.getInstance();

cal.setTime(dt); 
cal.add(Calendar.DATE, 15);  // Add 15 days

String output = sdf.format(cal.getTime());
System.out.println("Output :: "+output);

Upvotes: 2

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