RFR: 8305486: Add split() variants that keep the delimiters to String and j.u.r.Pattern [v2]

[Roger Riggs]

On Fri, 7 Apr 2023 14:11:36 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>> Add `split()` overloads to `String` and `java.util.regex.Pattern` that, in addition to the substrings returned by current `split()` variants, also return the delimiters matching the regular expression.
>
> Raffaello Giulietti has updated the pull request incrementally with one additional commit since the last revision:
> 
>   8305486: Add split() variants that keep the delimiters to String and j.u.r.Pattern
>   Restored original JavaDoc to existing methods.
>   Replaced proposed parametrized split(*, boolean) methods with suggested splitWithDelimiters(*) variants.
>   Adjusted tests accordingly.

src/java.base/share/classes/java/lang/String.java line 3237:

> 3235:      * the array are in the order in which they occur in this string.  If the
> 3236:      * expression does not match any part of the input then the resulting array
> 3237:      * has just one element, namely this string.

This paragraph duplicates part of the next paragraph.

src/java.base/share/classes/java/lang/String.java line 3253:

> 3251:      * string then an empty leading substring is included at the beginning
> 3252:      * of the resulting array. A zero-width match at the beginning however
> 3253:      * never produces such empty leading substring.

Is there any case in which it is ambiguous whether the first element is a string or delimiter?
I'm not sure what patterns could be zero-width.  But perhaps, a regex such as "^|\s", where one of the patterns could be zero-width and the other is non-zero width?
That could make the API hard to use.

src/java.base/share/classes/java/lang/String.java line 3302:

> 3300:      * <tr><!-- o -->
> 3301:      *     <th scope="row" style="font-weight:normal; text-align:right; padding-right:1em">0</th>
> 3302:      *     <td>{@code { "b", "o", "", "o", ":::and::f", "o", "", "o" }}</td></tr>

These cases might be a bit easier to understand if the regex matched characters that looked more like delimiters, perhaps just ":".

src/java.base/share/classes/java/lang/String.java line 3324:

> 3322:      *         the result threshold, as described above
> 3323:      *
> 3324:      * @return  the array of strings computed by splitting this string

Add a mention to the delimiters in the result.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/13305#discussion_r1161745116
PR Review Comment: https://git.openjdk.org/jdk/pull/13305#discussion_r1161756041
PR Review Comment: https://git.openjdk.org/jdk/pull/13305#discussion_r1161773124
PR Review Comment: https://git.openjdk.org/jdk/pull/13305#discussion_r1161790058