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.
// Java program to demonstrate conversion of// Set to array using simple traversalimport 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 }} |
Created ArrayList is Geeks for
Method 2 (Using ArrayList or LinkedList Constructor)
// Java program to demonstrate conversion of// Set to list using constructorimport 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); }} |
Created ArrayList is Geeks for Created LinkedList is Geeks for
Method 3 (Using addAll method)
// 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); }} |
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.
// Java program to demonstrate conversion of// Set to list using streamimport 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); }} |
Geeks for
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