AP® Computer Science A glossary
ConcurrentModificationException
Course: AP® Computer Science A Shows up in: Unit 4: Data Collections
The run-time exception that can be thrown when an ArrayList changes size while an enhanced for loop is traversing it.
Appears in the course and exam description (CED): 4.9.A.4
Do not call add or remove on a list inside an enhanced for loop over that list. To change the size during a traversal, use an indexed loop, for example traversing backward when removing.
ArrayList<String> cart = new ArrayList<String>();
cart.add("tea");
cart.add("milk");
cart.add("rice");
for (String item : cart)
{
cart.remove(0);
}Output:
Exception in thread "main" java.util.ConcurrentModificationException