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From Michael Osipov <>
Subject Re: [POOL2] Pooling mutable objects
Date Sat, 07 Feb 2015 09:23:48 GMT
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.



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