Re: [io] org.apache.commons.io.input.ReversedLinesFileReader.readLine(long)

[Gary Gregory]

On Wed, Mar 7, 2018 at 4:01 AM, sebb  wrote:

> On 7 March 2018 at 04:24, Gary Gregory  wrote:
> > On Tue, Mar 6, 2018 at 4:32 PM, sebb  wrote:
> >
> >> On 6 March 2018 at 23:22, Gary Gregory  wrote:
> >> > On Tue, Mar 6, 2018 at 4:13 PM, sebb  wrote:
> >> >
> >> >> On 6 March 2018 at 21:38, Gary Gregory 
> wrote:
> >> >> > Hi All:
> >> >> >
> >> >> > Any objection to adding:
> >> >> >
> >> >> > /**
> >> >> >  * Reads n lines from this reader.
> >> >> >  */
> >> >> > List
> >> >> > org.apache.commons.io.input.ReversedLinesFileReader.readLine(long
> >> >> lineCount)
> >> >> >
> >> >> > ?
> >> >>
> >> >> Yes.
> >> >>
> >> >> The name makes it sound like it is reading a single line, yet the
> >> >> output is a list of lines.
> >> >>
> >> >
> >> > Cut and paste error, obviously, the method should be called
> >> "readLines(long
> >> > lineCount)"
> >> >
> >> >
> >> >> Also, this seems like the sort of function that could be dealt with
> >> >> via a more general approach which would work with any method.
> >> >> AFAICT there would be no gain in embedding the looping code in IO
> >> >> rather than having it somewhere else.
> >> >>
> >> >
> >> > The gain is that your questions below would be defined by the new
> method.
> >>
> >> As they would by an independent method.
> >>
> >> >
> >> >> What happens if there aren't enough lines in the file?
> >> >>
> >> >
> >> > If you ask for 30 lines, and there are only 10 lines, you get 10
> lines.
> >> I'm
> >> > not sure what else could happen, you can't invent data that does not
> >> exist.
> >> >
> >> > What happens if there is an IO error reading one of the lines?
> >> >>
> >> >
> >> > Then the method throws an exception, just like readLine() does.
> >>
> >> So all the lines that have already been read are lost?
> >>
> >
> > Yes, just like all of the characters are lost when an exception is thrown
> > when you call readLine() today. Nothing shocking there IMO.
>
> So basically it is a simple loop around readLine(). Or is there some
> reason why it has to be part of IO?
>
> The method increases the cost of maintenance and the code size for
> something that is easy to code externally.
>
> Also, I'm not sure that the potential number of use cases warrants
> creating the code.
>

To me, this is the kind of boilerplate I want to avoid rewriting, and is
similar in spirit to org.apache.commons.io.IOUtils.readLines(Reader), which
is basically a loop.

More specifically, the class  ReversedLinesFileReader is documented to be
useful for log handling, which is what I am using it for. Like when I use
the tail command, I never want to process the whole file; "Just show me
then end N lines".

Gary

>
> > Gary
> >
> >
> >>
> >> > Would you
> >> > ask this question of readLine(): What happens if reading a single
> >> character
> >> > or a buffer of character causes an IO error?
> >> >
> >> > Gary
> >> >
> >> >
> >> >>
> >> >> > Gary
> >> >>
> >> >> 
> -
> >> >> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org
> >> >> For additional commands, e-mail: dev-h...@commons.apache.org
> >> >>
> >> >>
> >>
> >> -
> >> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org
> >> For additional commands, e-mail: dev-h...@commons.apache.org
> >>
> >>
>
> -
> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org
> For additional commands, e-mail: dev-h...@commons.apache.org
>
>

Re: [io] org.apache.commons.io.input.ReversedLinesFileReader.readLine(long)

[sebb]

On 7 March 2018 at 04:24, Gary Gregory  wrote:
> On Tue, Mar 6, 2018 at 4:32 PM, sebb  wrote:
>
>> On 6 March 2018 at 23:22, Gary Gregory  wrote:
>> > On Tue, Mar 6, 2018 at 4:13 PM, sebb  wrote:
>> >
>> >> On 6 March 2018 at 21:38, Gary Gregory  wrote:
>> >> > Hi All:
>> >> >
>> >> > Any objection to adding:
>> >> >
>> >> > /**
>> >> >  * Reads n lines from this reader.
>> >> >  */
>> >> > List
>> >> > org.apache.commons.io.input.ReversedLinesFileReader.readLine(long
>> >> lineCount)
>> >> >
>> >> > ?
>> >>
>> >> Yes.
>> >>
>> >> The name makes it sound like it is reading a single line, yet the
>> >> output is a list of lines.
>> >>
>> >
>> > Cut and paste error, obviously, the method should be called
>> "readLines(long
>> > lineCount)"
>> >
>> >
>> >> Also, this seems like the sort of function that could be dealt with
>> >> via a more general approach which would work with any method.
>> >> AFAICT there would be no gain in embedding the looping code in IO
>> >> rather than having it somewhere else.
>> >>
>> >
>> > The gain is that your questions below would be defined by the new method.
>>
>> As they would by an independent method.
>>
>> >
>> >> What happens if there aren't enough lines in the file?
>> >>
>> >
>> > If you ask for 30 lines, and there are only 10 lines, you get 10 lines.
>> I'm
>> > not sure what else could happen, you can't invent data that does not
>> exist.
>> >
>> > What happens if there is an IO error reading one of the lines?
>> >>
>> >
>> > Then the method throws an exception, just like readLine() does.
>>
>> So all the lines that have already been read are lost?
>>
>
> Yes, just like all of the characters are lost when an exception is thrown
> when you call readLine() today. Nothing shocking there IMO.

So basically it is a simple loop around readLine(). Or is there some
reason why it has to be part of IO?

The method increases the cost of maintenance and the code size for
something that is easy to code externally.

Also, I'm not sure that the potential number of use cases warrants
creating the code.

> Gary
>
>
>>
>> > Would you
>> > ask this question of readLine(): What happens if reading a single
>> character
>> > or a buffer of character causes an IO error?
>> >
>> > Gary
>> >
>> >
>> >>
>> >> > Gary
>> >>
>> >> -
>> >> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org
>> >> For additional commands, e-mail: dev-h...@commons.apache.org
>> >>
>> >>
>>
>> -
>> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org
>> For additional commands, e-mail: dev-h...@commons.apache.org
>>
>>

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Re: [io] org.apache.commons.io.input.ReversedLinesFileReader.readLine(long)

[Gary Gregory]

On Tue, Mar 6, 2018 at 4:32 PM, sebb  wrote:

> On 6 March 2018 at 23:22, Gary Gregory  wrote:
> > On Tue, Mar 6, 2018 at 4:13 PM, sebb  wrote:
> >
> >> On 6 March 2018 at 21:38, Gary Gregory  wrote:
> >> > Hi All:
> >> >
> >> > Any objection to adding:
> >> >
> >> > /**
> >> >  * Reads n lines from this reader.
> >> >  */
> >> > List
> >> > org.apache.commons.io.input.ReversedLinesFileReader.readLine(long
> >> lineCount)
> >> >
> >> > ?
> >>
> >> Yes.
> >>
> >> The name makes it sound like it is reading a single line, yet the
> >> output is a list of lines.
> >>
> >
> > Cut and paste error, obviously, the method should be called
> "readLines(long
> > lineCount)"
> >
> >
> >> Also, this seems like the sort of function that could be dealt with
> >> via a more general approach which would work with any method.
> >> AFAICT there would be no gain in embedding the looping code in IO
> >> rather than having it somewhere else.
> >>
> >
> > The gain is that your questions below would be defined by the new method.
>
> As they would by an independent method.
>
> >
> >> What happens if there aren't enough lines in the file?
> >>
> >
> > If you ask for 30 lines, and there are only 10 lines, you get 10 lines.
> I'm
> > not sure what else could happen, you can't invent data that does not
> exist.
> >
> > What happens if there is an IO error reading one of the lines?
> >>
> >
> > Then the method throws an exception, just like readLine() does.
>
> So all the lines that have already been read are lost?
>

Yes, just like all of the characters are lost when an exception is thrown
when you call readLine() today. Nothing shocking there IMO.

Gary


>
> > Would you
> > ask this question of readLine(): What happens if reading a single
> character
> > or a buffer of character causes an IO error?
> >
> > Gary
> >
> >
> >>
> >> > Gary
> >>
> >> -
> >> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org
> >> For additional commands, e-mail: dev-h...@commons.apache.org
> >>
> >>
>
> -
> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org
> For additional commands, e-mail: dev-h...@commons.apache.org
>
>

Re: [io] org.apache.commons.io.input.ReversedLinesFileReader.readLine(long)

[sebb]

On 6 March 2018 at 23:22, Gary Gregory  wrote:
> On Tue, Mar 6, 2018 at 4:13 PM, sebb  wrote:
>
>> On 6 March 2018 at 21:38, Gary Gregory  wrote:
>> > Hi All:
>> >
>> > Any objection to adding:
>> >
>> > /**
>> >  * Reads n lines from this reader.
>> >  */
>> > List
>> > org.apache.commons.io.input.ReversedLinesFileReader.readLine(long
>> lineCount)
>> >
>> > ?
>>
>> Yes.
>>
>> The name makes it sound like it is reading a single line, yet the
>> output is a list of lines.
>>
>
> Cut and paste error, obviously, the method should be called "readLines(long
> lineCount)"
>
>
>> Also, this seems like the sort of function that could be dealt with
>> via a more general approach which would work with any method.
>> AFAICT there would be no gain in embedding the looping code in IO
>> rather than having it somewhere else.
>>
>
> The gain is that your questions below would be defined by the new method.

As they would by an independent method.

>
>> What happens if there aren't enough lines in the file?
>>
>
> If you ask for 30 lines, and there are only 10 lines, you get 10 lines. I'm
> not sure what else could happen, you can't invent data that does not exist.
>
> What happens if there is an IO error reading one of the lines?
>>
>
> Then the method throws an exception, just like readLine() does.

So all the lines that have already been read are lost?

> Would you
> ask this question of readLine(): What happens if reading a single character
> or a buffer of character causes an IO error?
>
> Gary
>
>
>>
>> > Gary
>>
>> -
>> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org
>> For additional commands, e-mail: dev-h...@commons.apache.org
>>
>>

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Re: [io] org.apache.commons.io.input.ReversedLinesFileReader.readLine(long)

[Gary Gregory]

On Tue, Mar 6, 2018 at 4:13 PM, sebb  wrote:

> On 6 March 2018 at 21:38, Gary Gregory  wrote:
> > Hi All:
> >
> > Any objection to adding:
> >
> > /**
> >  * Reads n lines from this reader.
> >  */
> > List
> > org.apache.commons.io.input.ReversedLinesFileReader.readLine(long
> lineCount)
> >
> > ?
>
> Yes.
>
> The name makes it sound like it is reading a single line, yet the
> output is a list of lines.
>

Cut and paste error, obviously, the method should be called "readLines(long
lineCount)"


> Also, this seems like the sort of function that could be dealt with
> via a more general approach which would work with any method.
> AFAICT there would be no gain in embedding the looping code in IO
> rather than having it somewhere else.
>

The gain is that your questions below would be defined by the new method.


> What happens if there aren't enough lines in the file?
>

If you ask for 30 lines, and there are only 10 lines, you get 10 lines. I'm
not sure what else could happen, you can't invent data that does not exist.

What happens if there is an IO error reading one of the lines?
>

Then the method throws an exception, just like readLine() does. Would you
ask this question of readLine(): What happens if reading a single character
or a buffer of character causes an IO error?

Gary


>
> > Gary
>
> -
> To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org
> For additional commands, e-mail: dev-h...@commons.apache.org
>
>

Re: [io] org.apache.commons.io.input.ReversedLinesFileReader.readLine(long)

[sebb]

On 6 March 2018 at 21:38, Gary Gregory  wrote:
> Hi All:
>
> Any objection to adding:
>
> /**
>  * Reads n lines from this reader.
>  */
> List
> org.apache.commons.io.input.ReversedLinesFileReader.readLine(long lineCount)
>
> ?

Yes.

The name makes it sound like it is reading a single line, yet the
output is a list of lines.

Also, this seems like the sort of function that could be dealt with
via a more general approach which would work with any method.
AFAICT there would be no gain in embedding the looping code in IO
rather than having it somewhere else.

What happens if there aren't enough lines in the file?
What happens if there is an IO error reading one of the lines?

> Gary

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[io] org.apache.commons.io.input.ReversedLinesFileReader.readLine(long)

[Gary Gregory]

Hi All:

Any objection to adding:

/**
 * Reads n lines from this reader.
 */
List
org.apache.commons.io.input.ReversedLinesFileReader.readLine(long lineCount)

?

Gary