Given a linked list of line segments, remove middle points

removeMiddlePoints.java

// Given a linked list of co-ordinates where adjacent points either form a vertical line or a horizontal line. 
// Delete points from the linked list which are in the middle of a horizontal or vertical line.
// http://www.geeksforgeeks.org/given-linked-list-line-segments-remove-middle-points/
// The idea is to keep track of current node, next node and next-next node. 
// While the next node is same as next-next node, keep deleting the next node. 
// In this complete procedure we need to keep an eye on shifting of pointers and checking for NULL values.
class Node {
    
    int x;
    int y;
    Node next;
    
    Node(int a, int b)  
    { 
        x = a;
        y = b;
        next = null; 
    } 
}

class LinkedList
{
    Node head;  // head of list
 
    /* This function prints contents of linked list starting from head */
    public void printList()
    {
        Node temp = head;
        System.out.println( " Print Function ");
        while (temp != null)
        {
            System.out.println( "   Data: " + temp.x + "  " + temp.y);
            temp = temp.next;
        }
    }
    
    public static void main(String[] args)
    {
        LinkedList llist = new LinkedList();
 
        llist.head   = new Node(0,10);
        llist.addAtEnd(1,10);
        llist.addAtEnd(5,10);
        llist.addAtEnd(7,10);
        llist.addAtEnd(7,5);
        llist.addAtEnd(20,5);
        llist.addAtEnd(40,5);
        
        llist.printList();
        llist.remove();
        llist.printList();
        
    }
    
    public void remove()
    {
        Node current = this.head;
        Node next = null;
        Node next_next = null;
        
        while(current !=null && current.next !=null && current.next.next !=null)
        {
            next = current.next;
            next_next = current.next.next;
            if((current.x == next.x &&  current.x == next_next.x) ||
                  (current.y == next.y &&  current.y == next_next.y))
            {
                current.next = current.next.next;
            }
            else
            {
                current = current.next;
            }
        }
    }
    
    public void addAtHead(int x, int y)
    {
        Node node  = new Node(x, y);
        node.next  = this.head;
        this.head  = node;
    }
    
    public void addAtEnd(int x, int y)
    {
        Node node  = new Node(x, y);
        Node temp  = this.head;
        
        // find the tail node
        while(temp.next != null)
        {
            temp = temp.next;
        }
        
        temp.next = node;
    }
}