On Thu, 7 Sep 2023 11:13:44 GMT, Per Minborg <[email protected]> wrote:
> This PR outlines a solution for making immutable maps `@ValueBased` by
> removing cacheing of certain values in `AbstractMap`.
>
> By removing these caching fields in `AbstractMap`, we can make the immutable
> maps `@ValueBased` and at the same time, performance is likely improved
> because the JVM is probably able to optimize away object creation anyway via
> escape analysis. Also, all maps will occupy less space as we get rid of a
> number of objects and references stored for each map.
>
> We need to benchmark this solution to better understand its implications.
src/java.base/share/classes/java/util/AbstractMap.java line 375:
> 373: */
> 374: public Collection<V> values() {
> 375: return new AbstractCollection<>() {
Note that this causes `m.values().equals(m.values())` to no longer return
`true`, as base `Collection::equals` is defined using reference equality.
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PR Review Comment: https://git.openjdk.org/jdk/pull/15614#discussion_r1330553732
