RFR: 8376698: Add Spliterator tests for TreeMap sub-maps

[Chen Liang]

On Thu, 29 Jan 2026 22:22:57 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> The new cases for subMap in SpliteratorTraversingAndSplittingTest should be sufficient.
>
> I'd rather see it tested explicitly; its hard to identify exactly which test expects and catches the NPE.

The modification to that test adds new entries to a data provider. The NPE is checked by the preexisting testNullPointerException which tests all speliterators in the data set. I don't think an additional explicit unit test provides much value over the existing "cartesian" setup.

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PR Review Comment: https://git.openjdk.org/jdk/pull/29485#discussion_r2743827273