Parallel modification Exception thrown .next from Iterator

Question

Not sure what is wrong here:

    while(itr.hasNext())
    {
        Stock temp =itr.next();

    }

This code throws a ConcurrentModificationException in itr.next ();

Initializing an iterator private Iterator<Stock> itr=stockList.iterator();

Any ideas?

[The main code was copied directly from the professor’s slides]

Answer 1

There are two reasons for this.

• Another thread updates the inventory list directly or through its iterator
• In the same stream, possibly inside this cycle, the list of stocks changes (see example below)

The codes below may throw a ConcurrentModificationException

Iterator<Stock> itr = stockList.iterator();
 while(itr.hasNext()) 
    { 
        Stock temp = itr.next(); 

        stockList.add(new Stock()); // Causes ConcurrentModificationException 

        stockList.remove(0) //Causes ConcurrentModificationException 
    } 

Answer 2

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Answer 3

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javadoc:

, listIterator fail-fast: , , ConcurrentModificationException. , , , , .