Set to List in Java

Given a set (HashSet or TreeSet) of strings in Java, convert it into a list (ArrayList or LinkedList) of strings.

Input : Set hash_Set = new HashSet();
        hash_Set.add("Geeks");
        hash_Set.add("For");
Output : ArrayList or Linked List with 
         following content
         {"Geeks", "for"}

Method 1 (Simple)
We simply create an list. We traverse the given set and one by one add elements to the list.

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// Java program to demonstrate conversion of
// Set to array using simple traversal
import java.util.*;
  
class Test {
  public static void main(String[] args) {
  
    // Creating a hash set of strings
    Set<String> s = new HashSet<String>();
    s.add("Geeks");
    s.add("for");
  
    int n = s.size();
    List<String> aList = new ArrayList<String>(n);
    for (String x : s)
      aList.add(x);
  
    System.out.println("Created ArrayList is");
    for (String x : aList)
      System.out.println(x);
  
    // We can created LinkedList same way
  }
}

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Output:




Created ArrayList is
Geeks
for





Method 2 (Using ArrayList or LinkedList Constructor)











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// Java program to demonstrate conversion of 


// Set to list using constructor 


import java.util.*; 


  


class Test { 


  public static void main(String[] args) { 


        


    // Creating a hash set of strings 


    Set<String> s = new HashSet<String>(); 


    s.add("Geeks"); 


    s.add("for"); 


  


    // Creating an array list using constructor 


    List<String> aList = new ArrayList<String>(s); 


      


    System.out.println("Created ArrayList is"); 


    for (String x : aList) 


      System.out.println(x); 


  


    System.out.println("Created LinkedList is"); 


    List<String> lList = new LinkedList<String>(s);       


    for (String x : lList) 


      System.out.println(x);       


  } 


} 



















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Output:


Created ArrayList is
Geeks
for
Created LinkedList is
Geeks
for





Method 3 (Using addAll method)











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// Java program to demonstrate conversion of 


// Set to array using addAll() method. 


import java.util.*; 


  


class Test { 


  public static void main(String[] args) { 


  


    // Creating a hash set of strings 


    Set<String> s = new HashSet<String>(); 


    s.add("Geeks"); 


    s.add("for"); 


  


    List<String> aList = new ArrayList<String>(); 


    aList.addAll(s); 


  


    System.out.println("Created ArrayList is"); 


    for (String x : aList) 


      System.out.println(x); 


        


    List<String> lList = new LinkedList<String>(); 


    lList.addAll(s); 


  


    System.out.println("Created LinkedList is"); 


    for (String x : lList) 


      System.out.println(x);       


  } 


}



















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Output:


Created ArrayList is
Geeks
for
Created LinkedList is
Geeks
for





Method 4 (Using stream in Java)

We use stream in Java to convert given set to steam, then stream to list.  This works only in Java 8 or versions after that.











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// Java program to demonstrate conversion of 


// Set to list using stream 


import java.util.*; 


import java.util.stream.*; 


  


class Test { 


  public static void main(String[] args) { 


  


    // Creating a hash set of strings 


    Set<String> s = new HashSet<String>(); 


    s.add("Geeks"); 


    s.add("for"); 


  


    List<String> aList = s.stream().collect(Collectors.toList()); 


  


    for (String x : aList) 


      System.out.println(x); 


  } 


} 



















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Output:


Geeks
for








    

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