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From Phil Steitz <phil.ste...@gmail.com>
Subject Re: [POOL2] Pooling mutable objects
Date Sun, 08 Feb 2015 13:46:24 GMT




> On Feb 7, 2015, at 2:23 AM, Michael Osipov <1983-01-06@gmx.net> wrote:
> 
>> Am 2015-02-06 um 19:21 schrieb Phil Steitz:
>>> On 2/6/15 10:16 AM, sebb wrote:
>>> The existing Pool2 implementations use equals() to decide if two
>>> objects are the same.
>> 
>> As of pool 2.3.
>>> 
>>> You have to make sure that your equals() implementation returns true
>>> if and only if the objects being compared are the same as far as your
>>> use of them is concerned.
>>> So for example two Integers are equal if they have the same integral
>>> value, but two different StringBuffer instances are never equal.
>>> 
>>> Once you have determined what constitutes equality for your instances,
>>> make sure that the hash code is coded accordingly, i.e. two objects
>>> that are equal() must have the same hash code.
>>> If this requirment is not met, then the HashMap used internally by
>>> Pool2 will behave unpredictably.
>> 
>> Also, hash codes should not change between the time that an object
>> is borrowed from the pool and subsequently returned.  Again, for
>> pool 2.0-2.3 (latest as of this post), objects under management by
>> the pool are kept in a hashmap keyed on the objects themselves, so
>> mutability that changes hashcodes (and / or equality) can cause
>> problems.  See the discussion on POOL-284.
> 
> If this causes so many discussions and fuzz, it is worth filing another issue which should
document how a pooled object should like. Required criteria. That would have spared me the
searching.
> 

Definitely fixing javadoc and web site doco will be part of resolution of POOL-283/4.

Phil


> WDYT?
> 
> Michael
> 
> 
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