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From: laredotornado on 5 May 2010 15:33
Hi,

I'm using Java 1.6 on Mac 10.6.3. I'm trying to get the closest
Sunday before today, unless today is Sunday in which case I don't want
to change my calendar object. Here is what I have ...

cal.set(Calendar.DAY_OF_MONTH, 1);
while (cal.get(Calendar.DAY_OF_WEEK) != Calendar.SUNDAY) {
cal.add(Calendar.DAY_OF_YEAR, -1);
out.println("\t<!-- iterating through cal:" +
cal.getTime().toString() + "-->");
}

However, this loop is consistently returning a calendar instance that
is Saturday. Any ideas of something obvious that I'm missing here?

Thanks for your help, - Dave

From: markspace on 5 May 2010 16:12
laredotornado wrote:

> However, this loop is consistently returning a calendar instance that
> is Saturday. Any ideas of something obvious that I'm missing here?

This worked for me:

<code>
public class CalendarTest {
public static void main( String[] args )
{
Calendar c = Calendar.getInstance();
System.err.println( Calendar.SUNDAY );
System.err.println( c.get( Calendar.DAY_OF_WEEK ) );
while( c.get( Calendar.DAY_OF_WEEK ) != Calendar.SUNDAY ) {
c.roll( Calendar.DAY_OF_WEEK, -1 );
System.err.println( c.get( Calendar.DAY_OF_WEEK ) );
System.err.println( c.getTime() );
}

}
}
</code>
<output>
run:
1
4
3
Tue May 04 13:10:08 PDT 2010
2
Mon May 03 13:10:08 PDT 2010
1
Sun May 02 13:10:08 PDT 2010
BUILD SUCCESSFUL (total time: 1 second)
</output>

From: Lew on 5 May 2010 19:37
laredotornado wrote:
>> However, this loop is consistently returning a calendar instance that
>> is Saturday. Any ideas of something obvious that I'm missing here?

markspace wrote:
> This worked for me:
>
> <code>
> public class CalendarTest {
> public static void main( String[] args )
> {
> Calendar c = Calendar.getInstance();
> System.err.println( Calendar.SUNDAY );
> System.err.println( c.get( Calendar.DAY_OF_WEEK ) );
> while( c.get( Calendar.DAY_OF_WEEK ) != Calendar.SUNDAY ) {
> c.roll( Calendar.DAY_OF_WEEK, -1 );
> System.err.println( c.get( Calendar.DAY_OF_WEEK ) );
> System.err.println( c.getTime() );
> }
> }
> }
> </code>
> <output>
> run:
> 1
> 4
> 3
> Tue May 04 13:10:08 PDT 2010
> 2
> Mon May 03 13:10:08 PDT 2010
> 1
> Sun May 02 13:10:08 PDT 2010
> BUILD SUCCESSFUL (total time: 1 second)
> </output>

The problem there is the suspect definition of 'roll()':
"Adds the specified (signed) amount to the specified calendar field without
changing larger fields"

as opposed to 'add()', which reconciles the other fields.

--
Lew
From: Lew on 5 May 2010 20:04
laredotornado wrote:
> I'm using Java 1.6 on Mac 10.6.3. I'm trying to get the closest
> Sunday before today, unless today is Sunday in which case I don't want
> to change my calendar object. Here is what I have ...
>
> cal.set(Calendar.DAY_OF_MONTH, 1);

Are you quite certain you indented your code far enough? It's still readable,
so I think you didn't.


> while (cal.get(Calendar.DAY_OF_WEEK) != Calendar.SUNDAY) {
> cal.add(Calendar.DAY_OF_YEAR, -1);
> out.println("\t<!-- iterating through cal:" +
> cal.getTime().toString() + "-->");
> }

<http://sscce.org/>
<http://sscce.org/>
<http://sscce.org/>
<http://sscce.org/>
<http://sscce.org/>
<http://sscce.org/>
<http://sscce.org/>

Gosh darn it!

> However, this loop is consistently returning a calendar instance that
> is Saturday. Any ideas of something obvious that I'm missing here?

The problem, of course, is in the code you refused to show us because you
didn't provide an SSCCE.

Are you /trying/ to prevent us from helping you?

<sscce>
package eegee;

import java.util.Calendar;
import org.junit.Test;
import static org.junit.Assert.assertEquals;

public class Calendroll
{
@Test
public void test()
{
Calendar cal = Calendar.getInstance();
cal.set( Calendar.DAY_OF_MONTH, 1 );

findSunday( cal );
assertEquals( Calendar.SUNDAY, cal.get( Calendar.DAY_OF_WEEK ));

cal.set( Calendar.YEAR, 1999 );
cal.set( Calendar.MONTH, Calendar.DECEMBER );
cal.set( Calendar.DAY_OF_MONTH, 31 );

findSunday( cal );
assertEquals( Calendar.SUNDAY, cal.get( Calendar.DAY_OF_WEEK ));
}

private void findSunday( Calendar cal )
{
while (cal.get(Calendar.DAY_OF_WEEK) != Calendar.SUNDAY)
{
cal.add(Calendar.DAY_OF_YEAR, -1);
}
}
}
</sscce>

Works for me (running in JUnit framework).

--
Lew
From: markspace on 5 May 2010 20:41
Lew wrote:

> The problem there is the suspect definition of 'roll()':
> "Adds the specified (signed) amount to the specified calendar field
> without changing larger fields"
>
> as opposed to 'add()', which reconciles the other fields.
>


True, and I noticed that well after I posted. Still, at least my
example compiles, unlike the OP's.
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