java - iterator hasnext() returns true but next() throws NoSuchElementException

Question

When I debugged my code I found that the hasNext() method of Iterator returned true, but the next() method threw NoSuchElementException.

Below is my code:

 Collection<TradeStock> restBuy=em.createQuery("select t from TradeStock ...t.getResultList();

if(!restBuy.isEmpty())
{
    Iterator itrest=restBuy.iterator();
    while(itrest.hasNext())
    {
        TradeStock ts=(TradeStock)itrest.next();
        x+=ts.getTradeExecutedQuantity();
    }
}

What am I getting wrong?

Answer 1

When you say "debugged my code" do you mean debug using a debugger, like in Eclipse?
If your evaluated expression (Expressions tab in Eclipse) includes itrest.next() then the debugger invokes the next() method and modifies the state of your Iterator, without your code being aware of it.
Try debugging this either without evaluating itrest.next() or with log messages