How To Convert Hashset To Array

In Previous post we have learn how to convert Array to HashSet . In this post we will see how to convert set to array in java. We have following method for this

1. HashSet toArray() – convert to object array

toArray() method returns an array containing all of the elements in this collection. toArray() method return array of object.

import java.util.HashSet;

public class HashSetToArray {
	public static void main(String[] args) {
		  //Constructs a new, empty set
		   HashSet<String>	hashSet = new HashSet<String>();
		   
		   //add element in it 
		   hashSet.add("java");
		   hashSet.add("php");
		   hashSet.add("android");
		   
		   //display the element 
		   System.out.println("element in hashset ="+ hashSet);

		   /*
		    * Returns an array containing all 
		    * of the elements in this collection
		    */
		   Object[] array = hashSet.toArray();
		   
		   //print object type array
		   for (Object object : array) {
			System.out.println(object);
		  }

	}
}

Output:

element in hashset =[java, android, php]
java
android
php

2. ArrayList toArray(T[] a) – convert to string array

toArray(T[]a) method convert collection to String array or with the help this method we can convert hashset to int array. For this we will create a array with size of set and then pass as argument in toArray(T []a) method , and this method  return array  of element of set. if you want to more information about toArray() method and how it works internally please see this post ararylist to array example . Let’s see this by code.

import java.util.HashSet;

public class HashSetToArray2 {
	public static void main(String[] args) {
		  //Constructs a new, empty set
		   HashSet<String>	hashSet = new HashSet<String>();
		   
		   //add element in it 
		   hashSet.add("java");
		   hashSet.add("php");
		   hashSet.add("android");
		   
		   //display the element 
		   System.out.println("element in hashset ="+ hashSet);
		
		   String [] arr = new String[hashSet.size()];
		   
		   arr = hashSet.toArray(arr);
		   
		   //print object type array
		   for (String element : arr) {
			System.out.println(element);
		  }

	}

}

Output :

element in hashset =[java, android, php]
java
android
php

3. Native method

In this method we will iterate set and add one by one all element in array.

import java.util.HashSet;

public class HashSetToArray3 {
	
	public static void main(String[] args) {
		   //Constructs a new, empty set
		   HashSet<String>	hashSet = new HashSet<String>();
		   
		   //add element in it 
		   hashSet.add("java");
		   hashSet.add("php");
		   hashSet.add("android");
		   
		   //display the element 
		   System.out.println("element in hashset ="+ hashSet);
		
		   String [] arr = new String[hashSet.size()];
		   
		   int i =0;
		   for (String element : hashSet) {
			arr[i++] = element;
		   }

		   //print array
		   for (String element : arr) {
			System.out.println(element);
		}

		   
	}

}

Output:

element in hashset =[java, android, php]
java
android
php

A Guide to HashSet                                                                                                            Java Doc -HashSet

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