why use a hashset code example

Example: hashset in java

// java hashmap example
import java.util.HashMap;
public class HashMapExample 
{
   public static void main(String[] args) 
   {
      HashMap<Integer, String> hm = new HashMap<Integer, String>();
      // add elements
      hm.put(10,"Apple");
      hm.put(20,"Banana");
      hm.put(30,"Cherry");
      hm.put(40,"Dragonfruit");
      // print HashMap elements
      System.out.println("HashMap elements: " + hm);
   }
}