// 18B write a java code to demonstrate treeset
import java.util.*;
public class TestJavaCollection12{
  public static void main(String args[]){
    TreeSet<String> set = new TreeSet<>();
    set.add("Ravi");
    set.add("Vijay");
    set.add(null);
    set.add("Ravi");
    set.add("Ajay");
    Iterator<String> itr = set.iterator();
    while(itr.hasNext()){
      System.out.println(itr.next());
    }
  }
}