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Posted to dev@commons.apache.org by Gilles Sadowski <gi...@harfang.homelinux.org> on 2011/07/26 14:19:24 UTC
[Math] Confusing (?) use of "getInstance()" in formatting classes
Hi.
[This is related to issue MATH-622.]
Looking at the "CompositeFormat" and "RealVectorFormat", I notice an unusual
use of the "getInstance" method name. Unless I'm mistaken, "getInstance" is
most often used when the object stores a reference to a singleton. And in
those class, this does not seem to be the case: When I write
---
RealVectorFormat.getInstance().getFormat().setMaximumFractionDigits(6);
---
the output is unaffected, the default being to display 2 fraction digits),
which is not suitable for debugging.
I think that there should be a way to modify at once all outputs formatted
through "CompositeFormat", i.e. an actual singleton instance of "NumberFormat"
that is used by all "default" formatting.
Do you agree? Any caveats?
Regards,
Gilles
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Re: [Math] Confusing (?) use of "getInstance()" in formatting classes
Posted by Gilles Sadowski <gi...@harfang.homelinux.org>.
> >> > Hi.
> >> >
> >> > [This is related to issue MATH-622.]
> >> >
> >> > Looking at the "CompositeFormat" and "RealVectorFormat", I notice an unusual
> >> > use of the "getInstance" method name. Unless I'm mistaken, "getInstance" is
> >> > most often used when the object stores a reference to a singleton. And in
> >> > those class, this does not seem to be the case: When I write
> >> > ---
> >> > RealVectorFormat.getInstance().getFormat().setMaximumFractionDigits(6);
> >> > ---
> >> > the output is unaffected, the default being to display 2 fraction digits),
> >> > which is not suitable for debugging.
> >> >
> >> > I think that there should be a way to modify at once all outputs formatted
> >> > through "CompositeFormat", i.e. an actual singleton instance of "NumberFormat"
> >> > that is used by all "default" formatting.
> >> >
> >> > Do you agree? Any caveats?
> >>
> >> The singleton will need to be thread-safe.
> >>
> >> A mutable singleton is thread-hostile (*), so if this approach is
> >> taken, the Javadoc need to make this very clear.
> >
> > I don't particularly like it either but do you see another way?
>
> Yes - create the singleton once, with the required settings.
What do you mean? A little example maybe?
> > Yes, there is: To not use CM's formatting in the definition of the
> > "toString()" methods and/or overload them as
> > ---
> > public String toString(NumberFormat fmt) { /* ... */ }
> > ---
> > Then when debugging, one will be able to fairly easily write:
> > ---
> > RealVector v = new ArrayRealVector(new double[] {1.2345678, 2.3456789});
> > System.out.println("v=" + v.toString(CompositeFormat.getDefaultNumberFormat(8)));
> > ---
> >
> >> (*) Thread A sets the digit count, thread B sets it differently;
> >> thread A may not get the desired digit count.
> >
> > For debugging, the expectation is that the user sets it once, at the
> > top-level ("main"); so that will not be a problem usually.
>
> Yes, but my point is that the user needs to made aware of this.
We'll do that of course.
Gilles
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Re: [Math] Confusing (?) use of "getInstance()" in formatting classes
Posted by sebb <se...@gmail.com>.
On 26 July 2011 14:40, Gilles Sadowski <gi...@harfang.homelinux.org> wrote:
> On Tue, Jul 26, 2011 at 02:00:39PM +0100, sebb wrote:
>> On 26 July 2011 13:19, Gilles Sadowski <gi...@harfang.homelinux.org> wrote:
>> > Hi.
>> >
>> > [This is related to issue MATH-622.]
>> >
>> > Looking at the "CompositeFormat" and "RealVectorFormat", I notice an unusual
>> > use of the "getInstance" method name. Unless I'm mistaken, "getInstance" is
>> > most often used when the object stores a reference to a singleton. And in
>> > those class, this does not seem to be the case: When I write
>> > ---
>> > RealVectorFormat.getInstance().getFormat().setMaximumFractionDigits(6);
>> > ---
>> > the output is unaffected, the default being to display 2 fraction digits),
>> > which is not suitable for debugging.
>> >
>> > I think that there should be a way to modify at once all outputs formatted
>> > through "CompositeFormat", i.e. an actual singleton instance of "NumberFormat"
>> > that is used by all "default" formatting.
>> >
>> > Do you agree? Any caveats?
>>
>> The singleton will need to be thread-safe.
>>
>> A mutable singleton is thread-hostile (*), so if this approach is
>> taken, the Javadoc need to make this very clear.
>
> I don't particularly like it either but do you see another way?
Yes - create the singleton once, with the required settings.
> Yes, there is: To not use CM's formatting in the definition of the
> "toString()" methods and/or overload them as
> ---
> public String toString(NumberFormat fmt) { /* ... */ }
> ---
> Then when debugging, one will be able to fairly easily write:
> ---
> RealVector v = new ArrayRealVector(new double[] {1.2345678, 2.3456789});
> System.out.println("v=" + v.toString(CompositeFormat.getDefaultNumberFormat(8)));
> ---
>
>> (*) Thread A sets the digit count, thread B sets it differently;
>> thread A may not get the desired digit count.
>
> For debugging, the expectation is that the user sets it once, at the
> top-level ("main"); so that will not be a problem usually.
Yes, but my point is that the user needs to made aware of this.
>
> Gilles
>
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> To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
> For additional commands, e-mail: dev-help@commons.apache.org
>
>
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Re: [Math] Confusing (?) use of "getInstance()" in formatting classes
Posted by Gilles Sadowski <gi...@harfang.homelinux.org>.
On Tue, Jul 26, 2011 at 02:00:39PM +0100, sebb wrote:
> On 26 July 2011 13:19, Gilles Sadowski <gi...@harfang.homelinux.org> wrote:
> > Hi.
> >
> > [This is related to issue MATH-622.]
> >
> > Looking at the "CompositeFormat" and "RealVectorFormat", I notice an unusual
> > use of the "getInstance" method name. Unless I'm mistaken, "getInstance" is
> > most often used when the object stores a reference to a singleton. And in
> > those class, this does not seem to be the case: When I write
> > ---
> > RealVectorFormat.getInstance().getFormat().setMaximumFractionDigits(6);
> > ---
> > the output is unaffected, the default being to display 2 fraction digits),
> > which is not suitable for debugging.
> >
> > I think that there should be a way to modify at once all outputs formatted
> > through "CompositeFormat", i.e. an actual singleton instance of "NumberFormat"
> > that is used by all "default" formatting.
> >
> > Do you agree? Any caveats?
>
> The singleton will need to be thread-safe.
>
> A mutable singleton is thread-hostile (*), so if this approach is
> taken, the Javadoc need to make this very clear.
I don't particularly like it either but do you see another way?
Yes, there is: To not use CM's formatting in the definition of the
"toString()" methods and/or overload them as
---
public String toString(NumberFormat fmt) { /* ... */ }
---
Then when debugging, one will be able to fairly easily write:
---
RealVector v = new ArrayRealVector(new double[] {1.2345678, 2.3456789});
System.out.println("v=" + v.toString(CompositeFormat.getDefaultNumberFormat(8)));
---
> (*) Thread A sets the digit count, thread B sets it differently;
> thread A may not get the desired digit count.
For debugging, the expectation is that the user sets it once, at the
top-level ("main"); so that will not be a problem usually.
Gilles
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Re: [Math] Confusing (?) use of "getInstance()" in formatting classes
Posted by sebb <se...@gmail.com>.
On 26 July 2011 13:19, Gilles Sadowski <gi...@harfang.homelinux.org> wrote:
> Hi.
>
> [This is related to issue MATH-622.]
>
> Looking at the "CompositeFormat" and "RealVectorFormat", I notice an unusual
> use of the "getInstance" method name. Unless I'm mistaken, "getInstance" is
> most often used when the object stores a reference to a singleton. And in
> those class, this does not seem to be the case: When I write
> ---
> RealVectorFormat.getInstance().getFormat().setMaximumFractionDigits(6);
> ---
> the output is unaffected, the default being to display 2 fraction digits),
> which is not suitable for debugging.
>
> I think that there should be a way to modify at once all outputs formatted
> through "CompositeFormat", i.e. an actual singleton instance of "NumberFormat"
> that is used by all "default" formatting.
>
> Do you agree? Any caveats?
The singleton will need to be thread-safe.
A mutable singleton is thread-hostile (*), so if this approach is
taken, the Javadoc need to make this very clear.
(*) Thread A sets the digit count, thread B sets it differently;
thread A may not get the desired digit count.
>
> Regards,
> Gilles
>
> ---------------------------------------------------------------------
> To unsubscribe, e-mail: dev-unsubscribe@commons.apache.org
> For additional commands, e-mail: dev-help@commons.apache.org
>
>
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