Difference between Tree Set and Hash Set in Java

In Java, HashSet and TreeSet both belong to the collection framework. HashSet is the implementation of the Set interface, whereas TreeSet implements a sorted set. TreeSet is backed by TreeMap while HashSet is backed by a HashMap.

Difference Table

The following are the key differences between HashSet and TreeSet :

TreeSet

Syntax

The Following is the syntax of TreeSet :

TreeSet<String> treeset = new TreeSet<String>();

Example

Below is an example of a TreeSet in Java :

import java.util.TreeSet; 
public class TreeSetExmaple {
   public static void main(String[] args){
      TreeSet<String> treeset = new TreeSet<String>();
      treeset.add("Good");
      treeset.add("For");
      treeset.add("Health");
      //Add Duplicate Element
      treeset.add("Good");
      System.out.println("TreeSet : ");
      for (String temp : treeset) {
         System.out.println(temp);
      }
   }
}

Output

TreeSet:
   For
   Good
   Health

Time complexity: O(log n), due to Red-Black Tree operations.
Space complexity: O(n), stores elements in a balanced tree structure.

HashSet

Syntax

The Following is the syntax of HashSet :

HashSet<String> hashSet = new HashSet<String>();

Example

Below is an example of a HashSet in Java :

import java.util.HashSet; 
public class HashSetExample {
   public static void main(String[] args){
      HashSet<String> hashSet = new HashSet<String>();
      hashSet.add("Good");
      hashSet.add("For");
      hashSet.add("Health");
      //Add Duplicate Element
      hashSet.add("Good");
      System.out.println("HashSet: ");
      for (String temp : hashSet) {
         System.out.println(temp);
      }
   }
}

Output

HashSet:
   Health
   For
   Good

Time complexity: O(n), due to hash collisions.
Space complexity: O(n), stores elements in a Hash Table.