Re: Yet another ConcurrentModificationException question

From:

=?iso-8859-1?Q?Heiner_K=FCcker?= <mail@heinerkuecker.de>

Newsgroups:

comp.lang.java.help

Date:

Wed, 20 Aug 2008 09:58:27 +0200

Message-ID:

<g8giqv$52k$1@news01.versatel.de>

Eric Sosman schrieb

Heiner K?cker wrote:

Andy Chambers schrieb

Apologies for asking about this FAQ. I have looked up the relevant
java tutorial but I just want to check my understanding with the
following example.

Iterator oIterator = m_oCollection.iterator();
while( oIterator.hasNext()) {
           Element oElement = (Element)oIterator.next();
           String sOIDValue =
oElement.getAttribute(oElement.getOIDKey());
           if( sOIDValue != null && sOIDValue.equals(sElementOID) ) {
               // We have a match
               return oElement;
           }
       }

If I know that neither getAttribute() or getOIDKey() can alter the
"structure" of m_oCollection, is it true to say that a
ConcurrentModificationException thrown from within the body of the
while loop above, *must* have been caused by another thread altering
the structure of m_oCollection?

So to prevent this from happening, I can make m_oCollection a
synchronized Vector (currently it is just a normal vector), and put
this while loop inside a synchronized block.

Use a for loop , no iterator.

If you mean

for (Object obj : m_oCollection) {
Element oElement = (Element)obj;
}
... there *is* an Iterator, hidden by the syntax but present anyhow.

I dont mean the for each loop.

Use the for loop:

for ( int i = 0; i < vector.size() ; i++ )
{
    final Element oElement;
    /**
     * synchronized block for check
     * vector size and get element in
     * one atomar operation
     */
    synchronized( vector )
    {
        if ( i < vector.size() )
        {
            oElement = (Element)vector.get( i );
        }
        else
        {
            oElement = null;
        }
    } // synchronized

    if ( oElement != null )
    {
        your code
    }
}

--
Eric.Sosman@sun.com

--
Heiner K?cker
http://www.heinerkuecker.de
http://www.avon-beratung-terhorst.de