Java – LinkedHashSet

LinkedHashSet :

• The only difference between HashSet and LinkedHashSet is, HashSet does not maintain the insertion order of elements where as LinkedHashSet does it, using hashCode.
• LinkedHashSet since from jdk 1.4

import java.util.*;
class Demo 
{
	public static void main(String[] args) 
	{
		Random rand = new Random();
		LinkedHashSet set = new LinkedHashSet();
		for (int i=1 ; i<=5 ; i++)
		{
			int ele = rand.nextInt(100);
			set.add(ele);
			System.out.println("Element added : " + ele);
		}
		System.out.println("LinkedHashSet is : " + set);
	}
}

Iterator :

• It is an interface having pre-defined functions used to iterate Collection Object to process the elements.
• Much working like Enumeration.
• Iterator introduced in jdk 1.2 along with new implementations of Collection interface.
• To get Iterator object, we need to call iterator() method on any Collection instance.

Iterator <identifier> = Collection_Object.iterator();

import java.util.*;
class SetDemo 
{
	public static void main(String[] args) 
	{
		// HashSet set = new HashSet(); // No insertion order
		LinkedHashSet set = new LinkedHashSet(); // Maintain insertion order
		
		for(int i=10 ; i<=50 ; i+=10)
		{
			set.add(new Integer(i));
			set.add(new Integer(20));
		}

		System.out.println("Elements are : ");
		Iterator itr = set.iterator();
		while(itr.hasNext())
		{
			Integer i = (Integer)itr.next();
			System.out.println(i);
		}
	}
}