How to avoid “ConcurrentModificationException” while removing elements from `ArrayList` while iterating it? [duplicate]

Use an Iterator and call remove():
Iterator iter = myArrayList.iterator();

while (iter.hasNext()) {
String str = iter.next();

if (someCondition)
iter.remove();
}

As an alternative to everyone else’s answers I’ve always done something like this:
List toRemove = new ArrayList();
for (String str : myArrayList) {
if (someCondition) {
toRemove.add(str);
}
}
myArrayList.removeAll(toRemove);

This will avoid you having to deal with the iterator directly, but requires another list. I’ve always preferred this route for whatever reason.