In this article we will discuss how to Iterate over a HashSet in Java using HashSet.

Fetch Iterator from HashSet

To iterate over a HashSet we will use an Underlying Iterator object of the HashSet.

Fetch the Iterator from a HashSet object use its member function iterator() i.e.

// Create a HashSet of String
HashSet<String> setOfStrs = new HashSet<>();

// Fetch an Iterator object from HashSet Object
Iterator<String> it =  setOfStrs.iterator();

This iterator object will point to the starting of HashSet

How to Use the Iterator

Now with this Iterator object you can traverse over the elements of Set in forward direction using two member function i.e.

// It will check if next element exist or not
 boolean hasNext();

// It returns the next element from set
E next();

HashSet is not an ordered collection i.e. it can store elements in any order based on HashTable and hash codes. But iterator its guaranteed that we can iterate over all elements in a turn.

Now let’s see how to Iterate over a HashSet of String objects and print them one by one i.e.

package com.thispointer.java.collections.hashsets;

import java.util.HashSet;
import java.util.Iterator;

public class Example1 {

	public static void main(String[] args) {
		
		// Create a HashSet of String
		HashSet<String> setOfStrs = new HashSet<>();
		
		//Add String Objects to HashSet
		setOfStrs.add("hello");
		setOfStrs.add("abc");
		setOfStrs.add("time");
		setOfStrs.add("Hi");
		
		//Try to Add a duplicate element
		setOfStrs.add("abc");
		
		//Size of HashSet
		System.out.println("Set Size is = " + setOfStrs.size());

		// Fetch an Iterator object from HashSet Object
		Iterator<String> it =  setOfStrs.iterator();
		
		// Iterate till next element exists
		while(it.hasNext())
		{
			// Fetch the next element
			String data = it.next();
			System.out.println(data);
		}

	}

}

Output:
Set Size is = 4
Hi
abc
hello
time

 

 

We can call the size() member function of HashSet to fetch the current size of Hashset.

Join a list of 2000+ Programmers for latest Tips & Tutorials