RFR: 8303267: Prefer ArrayList to LinkedList in ConcurrentLocksPrinter

[Chris Plummer]

On Mon, 27 Feb 2023 12:54:24 GMT, Andrey Turbanov <aturbanov at openjdk.org> wrote:

> LinkedList is used as value in `sun.jvm.hotspot.runtime.ConcurrentLocksPrinter#locksMap` Map.
> There is only add/iterator calls on this lists. No removes from the head or something like this. Not sure why LinkedList was used, but ArrayList should be preferred as more efficient and widely used collection.
> 
> Also I've done some related code cleaned:
> 1. Mark field `locksMap` as final
> 2. Use Map.computeIfAbsent
> 3. Use enhanced-for cycle instead of `for` with iterator

Marked as reviewed by cjplummer (Reviewer).

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PR: https://git.openjdk.org/jdk/pull/12763