Insert, retrieve & remove record using TreeSet

TreeSetDemo.java

import java.util.*;
import java.util.Iterator;
import java.util.TreeSet;
class TreeSetDemo
{
    public static void main(String[] args)
    {
        TreeSet<Integer> set = new TreeSet<Integer>();
        set.add(21);
        set.add(11);
        set.add(14);
        set.add(15);
        set.add(23);
        set.add(24);
        Iterator<Integer> iterator = set.iterator();
        System.out.println("The elements of TreeSet");
        while (iterator.hasNext())
        {
            System.out.print(iterator.next()+" ");
        }
        System.out.println();
        if (set.isEmpty())
        {
            System.out.println("\nTreeSet is empty.");
        }
        else
            System.out.println("\nSize of the TreeSet: "+set.size());

        //fetching first and last data
        System.out.println("\nFirst element of TreeSet: "+set.first());
        System.out.println("Last element of TreeSet: "+set.last());
        //remove the element of TreeSet
        if (set.remove(23))
        {
            System.out.println("\nData 23 is deleted: ");
        }
        else
        {
            System.out.println("\nData is not present in TreeSet");
        }
        iterator = set.iterator();
        System.out.println("\nNow the elements of TreeSet");
        while (iterator.hasNext())
        {
            System.out.print(iterator.next()+" ");
        }
        System.out.println("\nSize of the TreeSet: "+set.size());
        //remove all element
        set.clear();
        if (set.isEmpty())
        {
            System.out.println("\nTreeSet is Empty.");
        }
        else
            System.out.println("Size of the TreeSet: "+set.size());
    }
}