Hi Gary, Peter,
Thanks again for the quick response and for pointing out the existing
capabilities in ArrayUtils and StringUtils..
I totally understand that this enhancement falls outside the current scope
or direction of Commons Lang. I truly appreciate your time and the
continued work the team puts into the project.
Looking forward to contributing in ways more aligned with the library in
the future!
Best regards,
Yokesh
On Mon, Jul 28, 2025 at 4:16 AM Peter Burka <pe...@quux.net> wrote:
> I agree that this feels way too pythonic to be in commons.
>
> FWIW, Python has some very powerful but idiosyncratic "slicing" idioms. For
> example (if I recall my python correctly),
>
> 0:-1 means from start to end (i.e. the whole array)
> 1:-2 means from the second to second-last element
> 0:-1:2 means every other element from start to end
> -1:0:-1 means the whole array, but reversed!
>
> The optional third term is the "step", which would more traditionally be
> called "stride".
>
> For further fun, the slice syntax actually creates slice objects. You can
> eschew the built-in slice type, and implement your own slice object using
> completely arbitrary indices. Want a slice based on the Fibonacci sequence?
> Not a problem!
>
> With a bit of clever stream chaining, these can all be in done in base
> Java, albeit more verbosely.
>
> Peter
>
> On Sun, Jul 27, 2025 at 3:20 PM Gary Gregory <garydgreg...@gmail.com>
> wrote:
>
> > On Sun, Jul 27, 2025 at 12:46 PM Yokesh Chowdary <
> > bollineniyok...@gmail.com>
> > wrote:
> >
> > > Hi Gary,
> > >
> > > Thanks for the quick reply!
> > >
> > > You're absolutely right, *ArrayUtils.subarray()* and
> > > *StringUtils.substring()
> > > *covers basic slicing. However, my proposal aims to enhance these
> methods
> > > by introducing:
> > >
> > > 1) Support for step
> > > ArrayUtils.slice(new int[]{1, 2, 3, 4, 5, 6}, 0, -1, 2); // returns [1,
> > 3,
> > > 5]
> > >
> > > 2) Support for negative indices
> > > StringUtils.slice("abcdef", -4, -1); // returns "cde"
> > >
> > > These enhancements bring Python-like expressiveness to Java, making
> > slicing
> > > more intuitive and concise for developers, especially when dealing with
> > > dynamic ranges or reverse slicing.
> > > Would love to hear thoughts on whether extending existing utils or
> > > introducing a SliceUtils would be preferable.
> > >
> >
> > Hello Yokesh,
> >
> > I think you're going to need to take a Java POV here, not Python, because
> > this:
> >
> > StringUtils.slice("abcdef", -4, -1); // returns "cde"
> >
> > feels nonsensical for this Commons component.
> >
> > In StringUtils, CharSequenceUtils, and ArrayUtils, negative indices are
> > usually (always?) errors.
> >
> > I don't think we should adopt the naming convention ("slice/SliceUtils")
> of
> > another language. Java and Commons Lang on top of it both have their own
> > vocabulary of APIs. In this case, Java uses "substring", and we're
> reusing
> > that term in StringUtils. In ArrayUtils, we derived that term into
> > "subarray".
> >
> > Adopting Python naming would set the expectation that this would maintain
> > the Python-ness behavior over time, and encourage further Python creep,
> > which is not what Commons components are about. They are about providing
> > Java-centric APIs, not "it works like X in language Y, so let's implement
> > that".
> >
> > There are odd bits in Lang to be sure, but that's mostly because the code
> > base has been around for a long time.
> >
> > WRT: ArrayUtils.slice(new int[]{1, 2, 3, 4, 5, 6}, 0, -1, 2); // returns
> > [1, 3,
> > 5]
> >
> > I have no idea how -1 makes sense or what these parameters mean. You'll
> > want to provide actual descriptions of each parameter so we know what
> > you're talking about. Assuming "it works like Python" is not a good idea.
> > Think about the whole class and how a new API fits in. Saying this lives
> in
> > a new class SliceUtils is not good IMO (see above on terminology).
> >
> > HTH,
> > Gary
> >
> >
> > > Regards,
> > > Yokesh
> > >
> > > On Sun, Jul 27, 2025 at 10:02 PM Gary Gregory <garydgreg...@gmail.com>
> > > wrote:
> > >
> > > > Hello Yokesh,
> > > >
> > > > This functionality already exists in ArrayUtils (subarray()) and
> > > > StringUtils (substring()).
> > > >
> > > > Gary
> > > >
> > > > On Sun, Jul 27, 2025, 12:06 Yokesh Chowdary <
> bollineniyok...@gmail.com
> > >
> > > > wrote:
> > > >
> > > > > Hi All,
> > > > >
> > > > > I'd like to propose adding a new utility method slice() to Apache
> > > Commons
> > > > > Lang that brings Python-style slicing capabilities to Java for
> > > > Collections,
> > > > > arrays (primitive and wrapper types), and String.
> > > > > The proposed method would follow the form: *slice(input, start,
> end,
> > > > step)*
> > > > >
> > > > > This would be a highly reusable utility that simplifies what is
> > > currently
> > > > > verbose or error-prone logic in standard Java. It could live in a
> new
> > > > class
> > > > > like *SliceUtils *or be integrated into existing utility classes
> such
> > > > > as *ArrayUtils
> > > > > *and *StringUtils*.
> > > > >
> > > > > *Highlights:*
> > > > > 1) Supports positive and negative indices for start,end and step
> > > > > 2) Works on Collections, Arrays and Strings
> > > > >
> > > > > *Examples:*
> > > > > List<String> names = Arrays.asList("Hello","Hi","Bye");
> > > > > SliceUtils.slice(names, 0,2); // returns ["Hello", "Hi"]
> > > > >
> > > > > String s = "abcdef";
> > > > > SliceUtils.slice(s, 1, 4); // returns "bcd"
> > > > >
> > > > > int[] numbers = {1, 2, 3, 4, 5, 6};
> > > > > SliceUtils.slice(numbers, 0, -1, 2); // returns [1, 3, 5]
> > > > >
> > > > > If the community agrees this is in scope for Commons Lang, I’d be
> > happy
> > > > to
> > > > > implement the feature with full test coverage and documentation.
> > > > >
> > > > > Looking forward to your thoughts.
> > > > >
> > > > > Regards,
> > > > > Yokesh
> > > > > [bollineniyok...@gmail.com]
> > > > >
> > > >
> > >
> >
>
