Java – Iterator Interface

Iterator:

• It is an interface.
• Iterator providing methods to iterator any collection.
• iterator() method returns Iterator object of any collection.

Methods:

1. boolean hasNext(): checks the next element is present or not to iterate.
2. Object next(): returns the next element of iterator object.

Program to display ArrayList using Iterator:

import java.util.*; class Code {             public static void main(String[] args)             {                         List<Integer> list = new ArrayList<Integer>();                         for(int i=1 ; i<=5 ; i++)                                     list.add(i*5);                                                 System.out.println(“Display using Iterator :”);                         Iterator<Integer> itr = list.iterator();                         while(itr.hasNext())                         {                                     Integer ele = itr.next();                                     System.out.println(ele);                         }             } }

When we use for/for-each/iterator?

For-loop	For-each loop	Iterator
Index based.	Not index based.	Not index based.
Process only List(index based)	Process List, Set and Map	Process List, Set and Map
Use get(index) method	Do not use any other method	Do not use any other method