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Convert Array to HashSet in Java
  • Last Updated : 28 Dec, 2020

The Single Data structure cannot be able to fulfill the requirements of the programmers that’s why there are a lot of inbuilt Data-Structures in Programming languages. 

Arrays are the most commonly used Data-Structure in most programming languages. The advantage of this Data-Structure is O(1) accessing the elements of the Arrays with the help of indexing but the most common disadvantages are we cannot change the size of the array after creating and the deletion of the elements is a complicated process in Arrays.

Sets: In Java, Any group of individual objects which are represented as a single unit is known as the collection of the objects. In Java, a separate framework named the “Collection Framework” has been defined in JDK 1.2 which holds all the collection classes and interface.  Sets are classified into two parts sorted set and unsorted set bot have advantage and disadvantage. Sorted Set i.e TreeSet sort its unique elements but the time-complexity of TreeSet is O(N log N) but unsorted Sets such as HashSet and LinkedSet do change the order of the elements but the difference between the HashSet and LinkedSet is Random Order of its elements.


Input : Array: [1, 2, 3, 4, 5, 6]
Output: Set: [1, 2, 3, 4, 5, 6]
Input : Array: [a, b, c, d]
Output: Set: [a, b, c, d]

Approach: Brute Force or Naive Method

Create an empty set  (HashSet if unsorted elements require) Iterate the elements of the array and add one by one to the set.



// Convert array to HashSet in Java
import java.util.Iterator;
// Importing Set libraries
import java.util.Set;
import java.util.HashSet;
class GFG {
    // Function to convert array to set
    static Set<Integer> convert(int[] array)
        // Hash Set Initialisation
        Set<Integer> Set = new HashSet<>();
        // Iteration using enhanced for loop
        for (int element : array) {
        // returning the set
        return Set;
    // Function to print the set
    static void print(Set<Integer> Set)
        // Implement to iterator the Set
        Iterator<Integer> _iterator = Set.iterator();
        // Iterate the elements of Set
        while (_iterator.hasNext()) {
            // print the element of the Set
            System.out.print( + " ");
    public static void main(String[] args)
        // Array taken for consideration
        int array[] = { 1, 2, 3, 4, 5, 6 };
        // Calling function to convert the array
        Set<Integer> Set = convert(array);
        // print the set
1 2 3 4 5 6

Approach 2

Using Java 8 Stream API: HashSet constructor can take another collection object to construct a new set containing the elements of the specified array.

  1. Get the Array to be converted.
  2. Convert the array to Stream
  3. Convert the Stream to Set using Collectors.toSet()
  4. Collect the formed set using the collect() method
  5. Return the formed Set.



// Convert Array to HashSet in Java
import java.util.*;
class GFG {
    // Generic function to convert array to set
    public static <T> Set<T> convertArrayToSet(T array[])
        // create a set from the Array
    public static void main(String args[])
        // Create an Array
        String array[]
            = { "Geeks", "forGeeks", "A computer Portal" };
        // Print the Array
        System.out.println("Array: "
                           + Arrays.toString(array));
        // convert the Array to Set
        Set<String> set = convertArrayToSet(array);
        // Print the Set
        System.out.println("Set: " + set);
Array: [Geeks, forGeeks, A computer Portal]
Set: [A computer Portal, Geeks, forGeeks]

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