On Wed, 21 Jan 2026 10:22:07 GMT, Eirik Bjørsnøs <[email protected]> wrote:
>> Please review this PR which proposes we replace `j.u.ArrayDeque` with
>> `j.u.ArrayList` in `jdk.internal.loader.URLClassPath`.
>>
>> The motivation for using a double-ended queue may have been that "original"
>> search path URLs are added to the tail of the queue while any URLs
>> discovered during JAR `Class-Path` expansion are inserted at the head such
>> that they are processed first.
>>
>> By splitting these two concerns and processing loader discovered class path
>> URLs separately from the original search path, we no longer need a
>> double-ended queue. We can replace `ArrayDeque` with `ArrayList`.
>>
>> Advantages:
>>
>> * A "hello world" Java program no longer loads `ArrayDeque`, `Deque` and
>> `Queue` (`URLClassPath` is the only consumer of these classes during startup
>> using a directory class path)
>> * One data structure is simpler than two
>> * We no longer need to manage search path URLs across two different
>> collections
>> * Code and comments to dance around `ArrayDeque` calling into lambda too
>> early is no longer a concern and can be removed
>> * I think this PR leaves the code overall simpler and easier to follow.
>>
>> Testing:
>>
>> This PR introduces a new test to verify that URLs disovered via a
>> multi-level tree paths discovered via `Class-Path` JAR attributes are found
>> in the expected DFS order. The ordering aspect seems to lack existing
>> coverage.
>
> Eirik Bjørsnøs has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Use "list" instead of "queue" when referring to expandedPath which is
> processed FIFO and as such is not a queue
src/java.base/share/classes/jdk/internal/loader/URLClassPath.java line 488:
> 486: * Adds the specified URLs to the list of 'Class-Path' expanded URLs
> 487: */
> 488: private void addExpandedPaths(URL[] urls) {
Once we rename the field to `manifestClassPath`, we should rename this method
to `addManifestClassPaths` too.
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PR Review Comment: https://git.openjdk.org/jdk/pull/29288#discussion_r2727651738
