Sequenced Collections

[Ernie Rael]

 > I don't see why you think a general collection...

I thought the Subject would be sufficient to indicate that I was not 
talking about collections in general. I should have been more precise 
with my words; guess I was just excited by a bi-directional ordered set.

The MRU _example_ is useful; the current collections handle it poorly 
and Sequenced Collections is ideal. Caches with an eviction policy are 
common; I suspect caches will be a common use for SequencedSet family. 
Note there are fixed sized Collections and SequencedCollection borrows 
heavily from that family. Perhaps this issue should be considered in the 
context of adding an **Eviction Policy** to appropriate collections.

MRU is a Collection; for example, I pass an MRU to a persistence 
mechanism that takes a collection. Saying "all methods offered by 
`Collection` should [not] even be part of an `MRU` interface" is 
innacurate, especially when considered in the context of a 
SequencedCollection.

-ernie

PS - Loosely related is extending a Collection and providing a 
synchronized version. Is there a discussion about making the 
SynchronizedCollection family of classes public?


On 9/21/22 4:22 AM, John Hendrikx wrote:
> I don't see why you think a general collection, that is in 99.9% of 
> the cases not used to implement an MRU, should burden every call to 
> #add with a check to see if it isn't exceeding its maximum size or to 
> see if a maximum size has been set.
>
> This is much better done by composition, as I don't think all methods 
> offered by `Collection` should even be part of an `MRU` interface.
>
> --John
>
> On 20/09/2022 21:08, Ernie Rael wrote:
>> (There may be a better place to send this, let me know where)
>>
>> Suggesting an option to limit the size of the collection, e.g 
>> "setMaxSize(int)", default of zero means no limit.
>>
>> I put together "interface MRU<E> extends Collection<E>" some months 
>> ago, it has two implementations based on LinkedList and 
>> LinkedHashSet. The code can be seen at 
>> https://sourceforge.net/p/jvi/raelity-lib/ci/default/tree/lib/src/main/java/com/raelity/lib/
>>
>> A SequencedCollection, as outlined in the JEP draft 2020/09/01, would 
>> be almost perfect to implement MRU; I've run into most of the 
>> problems/issues discussed in the JEP draft.
>>
>> The MRU is a cache, as I use it; it typically has a max size for the 
>> collection. Handling this natively in the collection would be ideal; 
>> if an add operation would overflow, remove the item at the other end. 
>> Note that addAll() is used when initializing from backing store.
>>
>> FYI, I use a "Supplier<Integer>" to the constructor to provide 
>> maxSize, but a property makes much more sense. I'll make that change 
>> in MRU for sanity, and get rid of the trim() method. setMaxSize can 
>> do the trim.
>>
>> -ernie
>>
>