Here is an example of HashSet example.

import java.util.*;

public class CollectFrame {
    public static void main(String [] args) {
        System.out.println( "Collection Example!\n" ); 
        //int size; 
        HashSet collection = new HashSet(); 
        String str1 = "Y",str2 = "W", str3 = "G", str4 = "B"; 
        //Iterator iterator;

        collection.add(str1); 
        collection.add(str2);
        collection.add(str3);
        collection.add(str4);
        Iterator itr = collection.iterator();

    System.out.println("HashSet contains : ");
    while(itr.hasNext())
      System.out.println(itr.next());
  }
}