在迭代Collection时删除元素

Question

I read that the correct way of removing elements while iterating the Collection, is this way (using iterator):

List<Integer> list = new ArrayList<Integer>();
list.add(12);
list.add(18);

Iterator<Integer> itr = list.iterator();

while(itr.hasNext()) {
    itr.remove();
}

But, I receive Exception in thread "main" java.lang.IllegalStateException and I don't know why. Can someone help me?

Answer 1

You never advanced to the next element by calling the next() method on the iterator. Try:

while(itr.hasNext()) {
    System.out.println("Removing " + itr.next());  // Call next to advance
    itr.remove();
}