Set vs HashSet vs TreeSet in Java

A Set is a generic set of values with no duplicate elements. A TreeSet is a set where the elements are sorted.

A HashSet is a set where the elements are not sorted or ordered. It is faster than a TreeSet. The HashSet is an implementation of a Set.

Set is a parent interface of all set classes like TreeSet, HashSet, etc.

Example

 Live Demo

import java.util.*;
public class Demo {
   public static void main(String args[]) {
      int a[] = {77, 23, 4, 66, 99, 112, 45, 56, 39, 89};
      Set<Integer> s = new HashSet<Integer>();
      try {
         for(int i = 0; i < 5; i++) {
            s.add(a[i]);
         }
         System.out.println(s);
         TreeSet sorted = new TreeSet<Integer>(s);
         System.out.println("Sorted list = ");
         System.out.println(sorted);
      } 
      catch(Exception e) {}
   }
}

Output

[66, 99, 4, 23, 77]
Sorted list =
[4, 23, 66, 77, 99]