Delete middle node from linked list in scala

Scala program for Delete middle node from linked list. Here problem description and explanation.

/*
    Scala program for
    Delete middle node of linked list
*/
// Linked list node
class LinkNode(var data: Int,
	var next: LinkNode)
{
	def this(data: Int)
	{
	
		this(data, null);
	}
}
class SingleLL(var head: LinkNode)
{
	def this()
	{
		this(null);
	}
	// Adding new node at beginning of linked list
	def addNode(data: Int): Unit = {
		// Create new node
		var node: LinkNode = new LinkNode(data);
		// Connect current node to previous head
		node.next = this.head;
		this.head = node;
	}
	// Display linked list element
	def display(): Unit = {
		if (this.head == null)
		{
			return;
		}
		var temp: LinkNode = this.head;
		// iterating linked list elements
		while (temp != null)
		{
			// Display node value
			print(""+ temp.data + " → ");
			// Visit to next node
			temp = temp.next;
		}
		print(" NULL\n");
	}
	// Delete the middle node of linked list
	def deleteMid(): Unit = {
		if (this.head == null)
		{
			// When linked list are no elements
			println("Empty Linked List");
		}
		else if (this.head.next == null && this.head.next.next == null)
		{
			// When linked list are less than  of 3 nodes
			println("Less then 3 node of linked list");
		}
		else
		{
			var temp: LinkNode = this.head;
			var midPrevious: LinkNode = null;
			// Find the middle and its previous node
			while (temp != null && temp.next != null && temp.next.next != null)
			{
				if (midPrevious == null)
				{
					// When first node
					midPrevious = temp;
				}
				else
				{
					// Visit to next node
					midPrevious = midPrevious.next;
				}
				// Visit to next second next node
				temp = temp.next.next;
			}
			// Get the node which is deleting 
			temp = midPrevious.next;
			// Show deleted node
			println("Delete node : " + temp.data);
			// Change link
			midPrevious.next = temp.next;
		}
	}
}
object Main
{
	def main(args: Array[String]): Unit = {
		var sll: SingleLL = new SingleLL();
		// Linked list
		// 7 → 6 → 5 → 4 → 3 → 2 → 1 → NULL
		sll.addNode(1);
		sll.addNode(2);
		sll.addNode(3);
		sll.addNode(4);
		sll.addNode(5);
		sll.addNode(6);
		sll.addNode(7);
		println("Before Delete middle node");
		sll.display();
		// Delete middle node
		sll.deleteMid();
		println("After Delete middle node");
		sll.display();
	}
}

Output

Before Delete middle node
7 → 6 → 5 → 4 → 3 → 2 → 1 →  NULL
Delete node : 4
After Delete middle node
7 → 6 → 5 → 3 → 2 → 1 →  NULL