#  RFR 8134512 : provide Alpha-Numeric (logical) Comparator

Peter Levart peter.levart at gmail.com
Fri Jul 28 14:12:27 UTC 2017

```Hi Ivan,

Would I be wrong if I described the logic of these two comparators as
the following:

The comparator compares two character sequences as though each of them
would be 1st transformed into a tuple of the form:

(A0, N0, A1, N1, ..., An-1, Nn-1, An)

where:

A0 and An are (possibly empty) sub-sequences consisting of
non-decimal-digit characters
A1 ... An-1 are non-empty sub-sequences consisting of non-decimal-digit
characters
N0 ... Nn-1 are non-empty sub-sequences consisting of decimal-digit
characters

...such that all sub-sequences concatenated together in order as they
appear in the tuple yield the original character sequence.

Any characher sequence can be uniquely transformed into such tuple. For
example:

"" -> (A0); where A0 == ""
"ab10" -> (A0, N0, A1); where A0 == "ab", N0 == "10", A1 = ""
"1" -> (A0, N0, A1); where A0 == "", N0 == "1", A1 = ""
...

After transformation, the tuples are compared by their elements (from
left to right) so that corresponding Ax elements are compared
lexicographically and Nx elements are compared as decimal integers (with

If I am right than perhaps such description would be easier to understand.

What do you think?

Regards, Peter

On 07/19/2017 10:41 AM, Ivan Gerasimov wrote:
> Hello!
>
> It is a proposal to provide a String comparator, which will pay
> attention to the numbers embedded into the strings (should they present).
>
> This proposal was initially discussed back in 2014 and seemed to bring
> some interest from the community:
> http://mail.openjdk.java.net/pipermail/core-libs-dev/2014-December/030343.html
>
>
> In the latest webrev two methods are added to the public API:
> j.u.Comparator.comparingNumerically() and