Delete last node of linked list in kotlin

Kotlin program for Delete last node of linked list. Here problem description and explanation.

/*
    Kotlin program for
    Delete the last node of singly linked list
*/
// Linked list node
class LinkNode
{
	var data: Int;
	var next: LinkNode ? ;
	constructor(data: Int)
	{
		this.data = data;
		this.next = null;
	}
}
class SingleLL
{
	var head: LinkNode ? ;
	var tail: LinkNode ? ;
	constructor()
	{
		this.head = null;
		this.tail = null;
	}
	// Add new node at the end of linked list
	fun addNode(value: Int): Unit
	{
		// Create a new node
		val node: LinkNode = LinkNode(value);
		if (this.head == null)
		{
			this.head = node;
		}
		else
		{
			this.tail?.next = node;
		}
		// Set new last node
		this.tail = node;
	}
	// Display linked list element
	fun display(): Unit
	{
		if (this.head == null)
		{
			println("Empty Linked List");
			return;
		}
		var temp: LinkNode ? = this.head;
		// iterating linked list elements
		while (temp != null)
		{
			print(""+ temp.data + " → ");
			// Visit to next node
			temp = temp.next;
		}
		println("NULL");
	}
	// Delete last node of singly linked list
	fun deleteLastNode(): Unit
	{
		if (this.head == null)
		{
			println("Empty Linked List");
			return;
		}
		else
		{
			var temp: LinkNode ? = this.head;
			var find: LinkNode ? = null;
			// Find second last node
			while (temp?.next != null)
			{
				find = temp;
				temp = temp.next;
			}
			if (find == null)
			{
				// Delete head node of linked list
				this.head = null;
				this.tail = null;
			}
			else
			{
				// Set new last node
				this.tail = find;
				find.next = null;
			}
		}
	}
}
fun main(args: Array < String > ): Unit
{
	val sll: SingleLL = SingleLL();
	// Linked list
	// 1 → 2 → 3 → 4 → 5 → 6 → NULL
	sll.addNode(1);
	sll.addNode(2);
	sll.addNode(3);
	sll.addNode(4);
	sll.addNode(5);
	sll.addNode(6);
	println("Before Delete ");
	sll.display();
	sll.deleteLastNode();
	println("After Delete ");
	sll.display();
}

Output

Before Delete
1 → 2 → 3 → 4 → 5 → 6 → NULL
After Delete
1 → 2 → 3 → 4 → 5 → NULL