Bag (Multiset) Collection

[ІП-24 Олександр Ротань]

Concurrent Bag is something like CopyOnWriteArrayList or Vector, don't we
have it already? (I know vectors aren't optimized). THe whole point of the
bag is to store duplicate elements without preserving order, which allows
things like ordered collections. There could be mutable collections for
concurrency optimized with read-write locks though, if that is what you are
referring to as "concurrent bag", and I am missing the point why this
can't be a part of list interface, then that just adds one more use case to
potential Bag interface.

PS: Ordered means it preserves order based on comparator, what you are
referring to as ordered essentially means sequential, or am I missing a
point?

сб, 20 апр. 2024 г. в 23:52, Holo The Sage Wolf <holo3146 at gmail.com>:

> By "ordered collection" you mean "unordered collection"?
>
> How common is it to actually use a multiset in general? Of course there
> are use cases, and there are areas in which it is used a lot, but I don't
> believe it is common enough to be part of the std with the one exception of
> concurrent bag.
>
> On Sat, 20 Apr 2024, 23:25 ІП-24 Олександр Ротань, <
> rotan.olexandr at gmail.com> wrote:
>
>> In this letter I would like to express some of my thoughts regarding the
>> potential Multiset interface.
>>
>> I, personally, have encountered a few situations where such an interface
>> could come in handy, mostly when I needed an ordered collection that
>> permits duplicates. That time I used guava`s TreeMultiset, but I think Java
>> itself should have such a collection in its std library. While it is not a
>> very common problem, there are still a bunch of use cases where such things
>> could come in handy.
>>
>> I am willing to take on development of such thing, but there are a few
>> concerns about Multiset:
>>
>> 1. Is there any other use for this besides ordered collection that
>> permits duplicates? I can't remember anything else from the top of my head.
>>
>> 2. Guava's TreeMultiset class hierarchy pretty much imitates TreeSet
>> class hierarchy, while not being directly connected. I think introducing
>> any other ordered collection will require some refactoring of existing
>> collection interfaces (for example extract SortedCollection from SortedSet,
>> Navigable Collection from NavigableSet etc.). From the perspective of clean
>> code, this would be the right decision, but I feel like this will be a very
>> complex task to accomplish.
>>
>> 3. Maybe there should be few versions of Tree collection (for example,
>> for regular tasks red-black tree and B-Tree for large amounts of data). I
>> have some expirience implementing both, but is it really needed in standard
>> library?
>>
>
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