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How to convert a set to a list in Java

Educative Answers Team

A Java set is a part of the java.util package; it extends the java.util.Collection interface. A Java set does not allow any duplicate item and allows only one null element.

A Java list is an ordered collection of items. Unlike a Java Set, a Java list can accommodate duplicate values.

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Conversion

There are two methods used to convert a set to a list:

  1. Adding all the elements of the set to the list individually.​
  2. Using the constructor of the list and passing the set to it.

Implementation of the first method

import java.util.*; 
import java.util.stream.*; 
  
class example { 
    
    // Generic function to convert set to list 
    public static <T> List<T> convertSetToList(Set<T> set) 
    { 
        // create an empty list 
        List<T> list = new ArrayList<>(); 
  
        // push each element in the set into the list 
        for (T t : set) 
            list.add(t); 
  
        // return the list 
        return list; 
    } 
    public static void main(String args[]) 
    { 
  
        // Create a Set using HashSet 
        Set<String> hash_Set = new HashSet<String>(); 
  
        // Add elements to set 
        hash_Set.add("Educative's"); 
        hash_Set.add("example"); 
        hash_Set.add("Set"); 
        hash_Set.add("to"); 
        hash_Set.add("list"); 
  
        // Print the Set 
        System.out.println("Set: " + hash_Set); 
  
        // construct a new List from Set 
        List<String> list = convertSetToList(hash_Set); 
  
        // Print the List 
        System.out.println("List: " + list); 
    } 
} 

Implementation of the second method

import java.util.*; 
import java.util.stream.*; 
  
class example { 
  
    // Generic function to convert set to list 
    public static <T> List<T> convertSetToList(Set<T> set) 
    { 
        // create a list from Set 
        List<T> list = new ArrayList<>(set); 
  
        // return the list 
        return list; 
    } 
  
    public static void main(String args[]) 
    { 
  
        // Create a Set using HashSet 
        Set<String> hash_Set = new HashSet<String>(); 
  
        // Add elements to set 
        hash_Set.add("Educative's"); 
        hash_Set.add("example"); 
        hash_Set.add("Set"); 
        hash_Set.add("to"); 
        hash_Set.add("list"); 
  
        // Print the Set 
        System.out.println("Set: " + hash_Set); 
  
        // construct a new List from Set 
        List<String> list = convertSetToList(hash_Set); 
  
        // Print the List 
        System.out.println("List: " + list); 
    } 
} 

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how
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