8357063: Document preconditions for DecimalDigits methods

[wenshao]

Similar to PR #24982
Document preconditions on certain DecimalDigits methods that use operations either unsafe and/or without range checks.

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Progress

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Issue

• JDK-8357063: Document preconditions for DecimalDigits methods (Enhancement - P4)

Reviewers

• Chen Liang (@liach - Reviewer)

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[rgiulietti]

@wenshao I understand this is a kind of followup of #24982, but why this title? It seems just renaming some methods with more speaking names.

[wenshao]

@wenshao I understand this is a kind of followup of #24982, but why this title? It seems just renaming some methods with more speaking names.

Yes, it is just a renaming of some methods, the title is followup #24982, does the same thing, so uses the same title

[rgiulietti]

The renaming is nice and useful.
But #24982, in addition to renaming, emphasizes the expectations about correct usage with bold WARNINGs in the JavaDoc. That's the "document preconditions" in the title.
Adding similar warnings in the JavaDoc, rather than in plain comments in the methods, would be clearer.

[vy]

Regarding all methods that are prefixed with unchecked in this PR, IMHO:

1. Precondition warnings should better be moved to the JavaDoc (ala 8353197: Document preconditions for JavaLangAccess methods #24982)
2. We shall also consider implementing these preconditions using assert statements

[vy]

@wenshao, thanks for the kind effort – dropped suggestions to match the messages with the ones in JLA.

I prefer all¹ public, unchecked-prefixed DecimalDigits methods to start with a sufficient assert preamble, to fail as early as possible. Though I don't want to create redundant extra work, hence double checking: @jaikiran, @minborg, @liach, WDYT?

¹ Currently, only two private methods are introduced asserts, which are fine.

[liach]

Re assert preamble for public methods: Unfortunately this is not possible. The algorithm requires the chars to be written on demand, and it is very costly to precompute the length, aside from the fact that you can easily mess up on precomputation. The uncheckedness is from the 2 private methods, so I think safeguarding the 2 private methods with assertions is sufficient.

[liach]

This version looks good to me. Please wait for a second confirmation. (Allowing authors like @vy to review too)

/reviewers 2

[openjdk]

@liach
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).