Removing duplicates in a linked list. Comparison using different methods.

gistfile1.java

package linkedlist;
import java.util.HashSet;
import java.util.Iterator;

class Node {
  int data;
	Node next;
	Node(int data){
		this.data = data;
		this.next = null;
	}
}

public class testlinkedlist {

	public Node add(int data, Node head){
		
		if(head == null){
			return head = new Node(data);
		}
		Node temp = head;
		while(temp.next != null){
			temp = temp.next;
		}
		temp.next = new Node(data);
		return head;
	}
	public void display(Node head){
		while(head != null){
			System.out.println(head.data);
			head = head.next;
		}
	}
	public boolean containsLoop(Node head){

		Node p1, p2;
		p1 = p2 = head;
		do {
			p1 = p1.next;
			p2 = p2.next.next;
		} while (p1 != p2);
		if(p1 == p2) return true;
		return false;
	}
	
	public Node removeDuplicate(Node head){
		Node p1, p2;
		p1 = head;
		while(p1 != null){
			p2 = p1.next;
			Node prev = p1;
			while(p2 != null){
				if(p1.data == p2.data){
					// there is a duplicate here
					// change the previous data to next
					prev.next = p2.next;
				}
				prev = p2;
				p2 = p2.next;
			}
			p1 = p1.next;
		}
		return head;
	}
	
	public Node removeDupsUsingList(Node head) {
		Node head2 = null;
		HashSet<Integer> set = new HashSet<Integer>();
		Node temp = head;
		while(temp != null){
			set.add(temp.data);
			temp = temp.next;
		}
		testlinkedlist tt = new testlinkedlist();
		for (Iterator iterator = set.iterator(); iterator.hasNext();) {
			Integer integer = (Integer) iterator.next();
			head2 = tt.add(integer, head2);
		}
		return head2;
	}
	/**
	 * @param args
	 */
	public static void main(String[] args) {
		
		long starttime1 = System.nanoTime();
		Node head = null;
		testlinkedlist tt = new testlinkedlist();
		head = tt.add(145, head);
		head = tt.add(451, head);
		head = tt.add(452, head);
		head = tt.add(425, head);
		head = tt.add(145, head);
		/**
		 * toggle below for finding the runtimes
		 */
		head = tt.removeDuplicate(head);
		head = tt.removeDupsUsingList(head);
		tt.display(head);
		long estimatedTime1 = System.nanoTime() - starttime1;
		System.out.println(estimatedTime1);
	}

}