How to convert an array to Set and vice versa in Java?

Array is a container which can hold a fix number of entities, which are of the same type. Each entity of an array is known as element and, the position of each element is indicated by an integer (starting from 0) value known as index.

Example

import java.util.Arrays;
public class ArrayExample {
   public static void main(String args[]) {
      Number integerArray[] = new Integer[3];
      integerArray[0] = 25;
      integerArray[1] = 32;
      integerArray[2] = 56;
      System.out.println(Arrays.toString(integerArray));
   }
}

Output

[25, 32, 56]

Whereas a Set object is a collection (object) stores another objects, it does not allow duplicate elements and allows at most null value.

Converting an array to Set object

The Arrays class of the java.util package provides a method known as asList(). This method accepts an array as an argument and, returns a List object. Use this method to convert an array to Set.

Example

import java.util.Arrays;
import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;
public class ArrayToSet {
   public static void main(String args[]){
      Scanner sc = new Scanner(System.in);
      System.out.println("Enter the size of the array to be created ::");
      int size = sc.nextInt();
      String [] myArray = new String[size];
      for(int i=0; i<myArray.length; i++){
         System.out.println("Enter the element "+(i+1)+" (String) :: ");
         myArray[i]=sc.next();
      }
      Set<String> set = new HashSet<>(Arrays.asList(myArray));
      System.out.println("Given array is converted to a Set");
      System.out.println("Contents of set ::"+set);
   }
}

Output

Enter the size of the array to be created ::
4
Enter the element 1 (String) ::
Ram
Enter the element 2 (String) ::
Rahim
Enter the element 3 (String) ::
Robert
Enter the element 4 (String) ::
Rajeev
Given array is converted to a Set
Contents of set ::[Robert, Rahim, Rajeev, Ram]

Set to array

The Set object provides a method known as toArray(). This method accepts an empty array as argument, converts the current Set to an array and places in the given array. Use this method to convert a Set object to an array.

Example

import java.util.HashSet;
import java.util.Set;
public class SetToArray {
   public static void main(String args[]){
      Set<String> set = new HashSet<String>();
      set.add("Apple");
      set.add("Orange");
      set.add("Banana");
      System.out.println("Contents of Set ::"+set);
      String[] myArray = new String[set.size()];
      set.toArray(myArray);
      for(int i=0; i<myArray.length; i++){
         System.out.println("Element at the index "+(i+1)+" is ::"+myArray[i]);
      }
   }
}

Output

Contents of Set ::[Apple, Orange, Banana]
Element at the index 1 is ::Apple
Element at the index 2 is ::Orange
Element at the index 3 is ::Banana

Maruthi Krishna

Published on 07-Aug-2019 11:40:51

• Related Questions & Answers
• Java Program to Convert the LinkedList into an Array and vice versa
• How to convert String to StringBuilder and vice versa Java?
• How to convert an integer to hexadecimal and vice versa in C#?
• How to Convert a String to Hexadecimal and vice versa format in java?
• Java Program to Convert contents of a file to byte array and Vice-Versa
• Convert string to DateTime and vice-versa in Python
• Java Program to Convert the ArrayList into a string and vice versa
• Converting Strings to Numbers and Vice Versa in Java.
• C++ Program to Convert Binary Number to Decimal and vice-versa
• C++ Program to convert Octal Number to Decimal and vice-versa
• C++ Program to Convert Binary Number to Octal and vice-versa
• Convert from any base to decimal and vice versa in C++
• How to convert a NumPy ndarray to a PyTorch Tensor and vice versa?
• C++ Program to Convert Km/hr to miles/hr and vice versa
• Binary to decimal and vice-versa in Python