What is Iterator and ListIterator

public interface Iterator<E> {
    E next();
    void remove();
}
JDK8 Iterator interfaces add default implementation for remove method and add another method: forEachRemaining with default method.
public interface Enumeration<E> {
    boolean hasMoreElements();
    E nextElement();
}

Why use Iterator when we have Enumerator:

Both Iterator and Enumerator is used for traversing of collection but Iterator is more enhanced in terms of extra method remove () it provide us for modify the collection which is not available in enumeration

What is List Iterator in Java?
interface ListIterator<E> extends Iterator<E>
{
  boolean hasNext();
  E next();
  boolean hasPrevious();
  E previous();
  int nextIndex();
  int previousIndex();
  void remove();
  void set(E paramE);
  void add(E paramE);
}
ListIterator in Java is an Iterator which allows user to traverse Collection like ArrayList and HashSet in both direction by using method previous() and next ().
2) If you want to remove objects from Collection than don't use for-each loop instead use Iterator's remove() method to avoid any ConcurrentModificationException.
3) Iterating over collection using Iterator is subject to ConcurrentModificationException if Collection is modified after Iteration started, but this only happens in case of fail-fast Iterators.
4) There are two types of Iterators in Java, fail-fast and fail-safe.
5) List collection type also supports ListIterator which has add() method to add elements in collection while Iterating.
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