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From "Leo Li" <liyilei1...@gmail.com>
Subject Re: [classlib][luni] Suspicious behavior of java.util.EnumSet
Date Mon, 21 Aug 2006 06:10:51 GMT
If so, we cannot regard it as RI's bug. And I believe the size of 64 and the
existence of the deleted element depends on RI's algorithm especially it
does not provide concurrent assurance. Maybe it is due to performance
concerns, I am not sure.
The curious thing is whether we should behave as RI since it says "it may or
may not show the effects of any modifications to the set that occur while
the iteration is in progress".


On 8/21/06, Spark Shen <smallsmallorgan@gmail.com> wrote:
>
> Leo Li 写道:
> > Hi, Spark:
> > Yes, I think it is RI's bug.
> > But It should throw ConcurrentModificationException as spec says:
> > 1. This exception may be thrown by methods that have detected
> > concurrent modification of an object when such modification is not
> > permissible.
> > 2. Note that this exception does not always indicate that an object has
> > been concurrently modified by a *different* thread. If a single thread
> > issues a sequence of method invocations that violates the contract of an
> > object, the object may throw this exception. For example, if a thread
> > modifies a collection directly while it is iterating over the collection
> > with a fail-fast iterator, the iterator will throw this exception.
> >
> > The iterator 's remove() action relies on the result of previous
> > next(), but is interrupted by the set.remove() method. I think it is the
> > case.
> >
> > Besides, If the same thing is applied to Hashset:
> > public static void main(String[] args) {
> > HashSet set = new HashSet();
> > Object o = new Object();
> > set.add(o);
> > Iterator iter = set.iterator();
> > iter.next();
> > set.remove(o);
> > iter.remove();
> > }
> > It will throw ConcurrentModificationException as expected.:)
> >
> >
> There is a paragraph from spec clearly states that
> ConcurrentModificationException will never be thrown out from the
> iterator returned
> by EnumSet. Cited below:
> "The returned iterator is /weakly consistent/: it will never throw
> |ConcurrentModificationException| <cid:part1.01020909.06080700@gmail.com>
> and it may or may not show the effects of any modifications to the set
> that occur while the iteration is in progress."
>
> Best regards
> > On 8/19/06, Spark Shen <smallsmallorgan@gmail.com> wrote:
> >>
> >> Hi All:
> >> The following behavior of RI java.util.EnumSet seems odd. Do you have
> >> any opinion on whether it is a bug of RI?
> >>
> >> import java.util.EnumSet;
> >> import java.util.Iterator;
> >> public class Test {
> >> static enum EnumFoo {
> >> a, b,
> >> }
> >>
> >> public static void main(String[] args){
> >> EnumSet<EnumFoo> set = EnumSet.noneOf(EnumFoo.class);
> >> set.add(EnumFoo.a);
> >> Iterator<EnumFoo> iterator = set.iterator();
> >> iterator.next();
> >>
> >> set.remove(EnumFoo.a);
> >> iterator.remove(); (1)
> >> // The output value is true
> >> System.out.println(set.contains(EnumFoo.a));
> >> // The output value is 64
> >> System.out.println(set.size());
> >> }
> >> }
> >> IMHO, when (1) is executed, an IllegalStateException should be thrown
> >> out, since the element EnumFoo.a does not exist at the moment.
> >> Any thoughts?
> >>
> >> Best regards
> >>
> >> --
> >> Spark Shen
> >> China Software Development Lab, IBM
> >>
> >>
> >> ---------------------------------------------------------------------
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> >>
> >>
> >
> >
>
>
> --
> Spark Shen
> China Software Development Lab, IBM
>
>
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>
>


-- 
Leo Li
China Software Development Lab, IBM

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