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Bug ID:
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6486197
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Votes
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0
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Synopsis
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ConcurrentHashMap.get should check key identity before equality
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Category
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java:classes_util_concurrent
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Reported Against
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Release Fixed
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State
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5-Cause Known,
request for enhancement
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Priority:
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5-Very Low
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Related Bugs
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Submit Date
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25-OCT-2006
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Description
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A DESCRIPTION OF THE REQUEST :
The HashMap implementation short circuits the case of the same key which avoids the potentially more costly equals() comparison at the cost of an extra comparison.
JUSTIFICATION :
Faster when using common keys
ACTUAL -
Current 1.6 HashMap:
if (e.hash == hash && ((k = e.key) == key || key.equals(k)))
Current 1.6 ConcurrentHashMap:
if (e.hash == hash && key.equals(e.key))
Posted Date : 2006-10-25 16:08:04.0
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Work Around
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N/A
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Evaluation
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I can think of no reason why such an optimization
would not apply to both HashMap and ConcurrentHashMap,
as the submitter suggests.
Many equals methods first check for identity themselves,
so there is often a very small amount of double work being
done when optimizing this way. But more and more,
comparing two values in registers is considered "free".
Posted Date : 2006-10-25 17:16:49.0
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Comments
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PLEASE NOTE: JDK6 is formerly known as Project Mustang
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