Re: Getting java.util.ConcurrentModificationException

Lew <>
Fri, 08 Aug 2008 08:31:40 -0400
<> wrote:

I have written a game that using min max algorithm, with Vector as

Don't use Vector, use ArrayList.

it's [sic] tokens and in the algorithm it makes a move and check it's [sic] value
and then return to original values, but when i [sic] try to use the vector [sic]
again it gives me the exception above,

You have not cited the exception - where is the copy-and-paste of the message?

that i [sic] altered it and therefor i [sic] cannot continue.
i [sic] have tried to create a clone of the vetctor [sic] so it won't be using the
original vactor [sic] and work on the copy but it didnt work.
someone have an idea to help me outa here i [sic] am helpless.

RedGrittyBrick wrote:

Having multiple threads can make for problems. But often good use of
threads is essential.

ConcurrentModificationException can occur in a single-threaded context. It is
thrown when one changes a collection structurally while it's in use by another

I'd start here

Others in this newsgroup have recommended the book "Java Concurrency in
Practice" by Brian Goetz. I haven't read it.

Joshua Bloch's "Effective Java" (2nd Ed) covers concurrency in Chapter 10.

Maybe you are modifying your Vector in one thread whilst an iterator is
being used in another? Maybe your clone is shallow?

For more direct help, I'd create an SSCCE -

P.S. Whilst your English is far far better than my <insert other
language of your choice here>, long sentences with poor capitalisation
and punctuation are harder for me to read. Please take your time when
composing a question.

<> please.

Find the place in the code that changes the Vector (or ArrayList) before
another place is through with it. With an SSCCE we can help. Without
information, that very information you have so far declined to share, we cannot.


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