Difference between an Iterator and ListIterator in Java

Iterator and ListIterator are interfaces provided by the Java Collection Framework to traverse collection elements one by one. Iterator is used for simple forward traversal of collections like List, Set, and Queue, whereas ListIteratorprovides advanced features such as backward traversal, element modification, and insertion in List collections.

• Iterator moves only forward, while ListIterator moves forward and backward.
• Iterator works for all collections, while ListIterator works only for List classes.

Iterator

Iterator is an interface available in the java.util package. It is mainly used to iterate through collection elements one at a time.

• Supports read and remove operations.
• Cannot add or replace elements during traversal.

Syntax

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

Elements using Iterator:
10
20
30

Explanation: In this example, the Iterator object traverses the ArrayList in forward direction using hasNext() and next() methods.

ListIterator

ListIterator is an interface that extends Iterator. It is used only for List collections and supports both forward and backward traversal.

• Allows adding, updating, and removing elements.
• Provides index-based methods like nextIndex() and previousIndex().

Syntax

ListIterator<Integer> ltr = list.listIterator();

Forward Traversal:
1
2
3
Backward Traversal:
3
2
1

Explanation: In this example, ListIterator traverses the ArrayList in both forward and backward directions using next() and previous() methods.

Example: ListIterator can help to replace an element whereas Iterator cannot

Elements of ArrayList: 
1
2
3
4
5

Now the ArrayList elements are: 
80000
2
3
4
5

Iterator vs ListIterator