In Java Collections, Iterator and ListIterator are two interfaces that allow you to iterate over a collection of elements. While they both have similar functionality, there are some differences that make them useful in different scenarios.
Iterator:
Iterator is a basic interface in the Java Collections Framework that can be used to traverse any collection that implements the Iterable interface. It is used for iterating over a collection of elements in a forward direction only. It can remove elements from the collection during iteration. It has three methods: hasNext(), next(), and remove().
Example Code:
List<String> list = new ArrayList<>();
list.add("Apple");
list.add("Banana");
list.add("Mango");
Iterator<String> iterator = list.iterator();
while (iterator.hasNext()) {
String element = iterator.next();
System.out.println(element);
if (element.equals("Banana")) {
iterator.remove();
}
}ListIterator:
ListIterator is an extended interface of Iterator that can be used to traverse only those collections that implement the List interface. It is used for iterating over a list of elements in both forward and backward directions. It can add, remove, and replace elements in the list during iteration. It has eight methods: hasNext(), next(), hasPrevious(), previous(), nextIndex(), previousIndex(), remove(), and set().
Example Code:
List<String> list = new ArrayList<>();
list.add("Apple");
list.add("Banana");
list.add("Mango");
ListIterator<String> listIterator = list.listIterator();
while (listIterator.hasNext()) {
String element = listIterator.next();
System.out.println(element);
if (element.equals("Banana")) {
listIterator.add("Orange");
listIterator.remove();
}
}When to use Iterator or ListIterator:
If you want to iterate over a collection in a forward direction and you don’t need to modify the collection while iterating, use an Iterator. If you want to iterate over a list in both forward and backward directions and you need to modify the list while iterating, use a ListIterator.