In this post, we will see difference between Iterator and ListIterator in java. They are both used for traversal but it is good to point out differences between them.
Iterator vs ListIterator:
|
Parameter
|
Iterator
|
ListIterator
|
|---|---|---|
|
Traversal
|
Iterator can be used to traverse List,set, Queue
|
ListIterator can be used to traverse only List.
|
|
Traversal direction
|
Iterator can be traversed only in forward direction |
ListIterator can be traverse in forward direction as well backward.
|
|
You can not add elements while traversing using Iterator. It will through ConcurrentModificationException
|
You can add elements while traversing using ListIterator.
|
|
|
Replacing existing elements
|
You can not replace exisitng elements while traversing using Iterator.
|
You can replace exisitng elements while traversing using ListIterator using set(E e).
|
|
Accessing Index
|
You can not access index using Iterator
|
You can access index using ListIterator via nextIndex() or previousIndex methods
|
Example:
1. Country.java
package org.arpit.java2blog;
public class Country {
String name;
long population;
public Country(String name, long population) {
super();
this.name = name;
this.population = population;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public long getPopulation() {
return population;
}
public void setPopulation(long population) {
this.population = population;
}
}
2. IterateListMain.java
package org.arpit.java2blog;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.ListIterator;
public class IterateListMain {
/**
* @author Arpit Mandliya
*/
public static void main(String[] args) {
Country india=new Country("India",1000);
Country japan=new Country("Japan",10000);
Country france=new Country("France",2000);
Country russia=new Country("Russia",20000);
// We are going to iterate on this list and will print
//name of the country
ArrayList countryLists=new ArrayList();
countryLists.add(india);
countryLists.add(japan);
countryLists.add(france);
countryLists.add(russia);
System.out.println("-----------------------------");
// Iterator
System.out.println("Iterating using iterator : ");
Iterator iteratorCountryLists= countryLists.iterator();
while(iteratorCountryLists.hasNext())
{
System.out.println(iteratorCountryLists.next().getName());
}
System.out.println("-----------------------------");
//List iterator
System.out.println("Iterating using ListIterator in forward direction : ");
ListIterator listIteratorCountry= countryLists.listIterator();
while(listIteratorCountry.hasNext())
{
System.out.println(listIteratorCountry.next().getName());
}
System.out.println("-----------------------------");
System.out.println("Iterating using ListIterator in backward direction : ");
while(listIteratorCountry.hasPrevious())
{
System.out.println(listIteratorCountry.previous().getName());
}
}
}
When you run above program, you will get following output:
----------------------------- Iterating using iterator : India Japan France Russia ----------------------------- Iterating using ListIterator in forward direction : India Japan France Russia ----------------------------- Iterating using ListIterator in backward direction : Russia France Japan India
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