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How to Print HashSet Elements in Java?
  • Last Updated : 15 Dec, 2020

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:

  1. Using the iterator() method to traverse the set elements and printing it.
  2. 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.
        // Inserton 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 dont't know hash code,
        // so we don't know order
        // of insertion
        System.out.println(hs);
    }
}
Output
[A, B, C, D, null, Z, 10]

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