isEqualSet method in SetUtils could rehash the two input sets before it does
the containsAll comparison
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Key: COLLECTIONS-311
URL: https://issues.apache.org/jira/browse/COLLECTIONS-311
Project: Commons Collections
Issue Type: Improvement
Components: Set
Affects Versions: 3.2
Reporter: Michael Qiu
Hey Guys
I had an interesting problem recently where I was comparing 2 sets and the
equals method was returning false... maybe it might be easier to understand if
I explain using pseudo code:
{code}
set1.equals(set2) = false
set1.get(0).equals(set2.get(0)) = true
set1.get(1).equals(set2.get(1)) = true
set1.get(0).hashCode() == set2.get(0).hashCode() = true
set1.get(1).hashCode() == set2.get(1).hashCode() = true
{code}
So, objects in the two sets are equals, the hashCode of the objects in the two
sets are equals, however the equals comparison at the set level was not equals.
After some time, we figured out that the problem was that the object inside the
set was getting modified after it was put into the set. So the new hashCode of
the object has changed. However the bucket of the set that it's in hasn't
changed. When another piece of code calls the contains method, it looks for
the equivalent object in a bucket according to the new hashCode. When it
doesn't find it, and it returns false.
I would like to suggest that the SetUtils.isEqualSet method rehashes contents
of the sets given in the parameters before it does the containsAll comparison
to avoid the problem caused by this scenario.
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