Re: Yet another ConcurrentModificationException question

Eric Sosman <>
Tue, 19 Aug 2008 17:17:36 -0400
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);
           String sOIDValue =
           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.
It's a bit like

    System.out.println("Hello, " + System.getProperty(""));

.... where a StringBuilder is used even though you don't see it
mentioned in the source code.


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