RFR 8081027: Create a common test to check adequacy of initial size of static HashMap/ArrayList fields

[Martin Buchholz]

Approved.

On Thu, May 28, 2015 at 3:43 PM, Ivan Gerasimov <ivan.gerasimov at oracle.com>
wrote:

Good naming is one of the most difficult part of coding IMO.
> The chosen names were meant to be read literally: "optimal capacity of
> ArrayList", etc.
> I agree, 'assert' would tell more about these methods' intention, but I'm
> not sure how to include it in the names.
> Maybe rename the class to AssertOptimalCapacity?
>
>
Assertions are a class of names we are used to importing statically. Junit
and Testng both have collections of static methods named assertXXX.


>  For ArrayLists, I would have been happy enough just testing that we have
> 100% utilization, i.e. size of array is the same as size of the List,
> without checking the initial capacity.
>
>   But then the test wouldn't have caught the "bug" in
> src/java.base/share/classes/sun/security/ssl/ExtensionType.java
> The ArrayList was pre-sized to 9, and after reallocation the capacity
> happened to become (9 + 9/2) = 13, which by coincidence is the final size
> of the List.
>

It's a tradeoff of maintenance burden vs performance.  Note also that
oversize is a much bigger performance bug than undersize because you pay
for it for the entire process, not just startup.