Node.java

public class Node {
 int data;
 Node next, prev;

 public Node() {
 data = 0;
 next = prev = null;
 }

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

 public Node(Node x) {
 data = x.data;
 next = x.next;
 prev = x.prev;
 }

 @Override
 public int hashCode() {
 return data;
 }

 @Override
 public boolean equals(Object obj) {
 if (obj instanceof Node) {
 Node n = (Node) obj;
 return data == n.data;
 } else
 return false;
 }
}