How to Print HashSet Elements in Java?

Last Updated : 09 Jan, 2023

In HashSet, duplicates are not allowed. If we are trying to insert duplicates then we won't get any compile-time or runtime error and the add() method simply returns false.

We can use 2 ways to print HashSet elements:

Using the iterator() method to traverse the set elements and printing it.
Directly printing it using a reference variable.

Method 1: By using Cursor which is Iterator.

If we want to get objects one by one from the collection then we should go for the cursor.
We can apply the Iterator concept for any Collection Object and hence it is a Universal Cursor.
By using Iterator we can perform both read and remove operations.
We can create an Iterator object by using the iterator method of Collection Interface.

public Iterator iterator(); // Iterator method of Collection Interface.

Creating an iterator object

Iterator itr = c.iterator(); // where c is any Collection Object like ArrayList,HashSet etc.

Example:

Java

// Java program to print the elements
// of HashSet using iterator cursor

import java.util.*;

class GFG {
    public static void main(String[] args)
    {

        HashSet<Integer> hs = new HashSet<Integer>();
        hs.add(5);
        hs.add(2);
        hs.add(3);
        hs.add(6);
        hs.add(null);

        // print HashSet elements one by one.
        // Insertion order in not preserved and it is based
        // on hash code of objects.

        // creates Iterator oblect.
        Iterator itr = hs.iterator();

        // check element is present or not. if not loop will
        // break.
        while (itr.hasNext()) {
            System.out.println(itr.next());
        }
    }
}

Output

null
2
3
5
6

Method 2: We can directly print HashSet elements by using the HashSet object reference variable. It will print the complete HashSet object.

Note: If we do not know the hash code, so you can't decide the order of insertion.

Example:

Java

// Java program to directly print the
// elements of HashSet

import java.util.*;

class GFG {
    public static void main(String[] args)
    {

        // create HashSet object
        HashSet<String> hs = new HashSet<String>();

        // add element in HashSet object
        hs.add("B");
        hs.add("C");
        hs.add("D");
        hs.add("A");
        hs.add("Z");
        hs.add("null");
        hs.add("10");

        // print HashSet
        // we don't know hash code,
        // so we don't know order
        // of insertion
        System.out.println(hs);
    }
}