Custom generic Linked List implementation in Java for Interview Problems.

CustomLinkedList.java

/*
 * Custom generic Linked List implementation in Java.
 * This class is for working with Linked List related interview problems.
 * 
 * It is intended to be extended with a Type paramater as follows:
 *
 * class PracticeSoln extends CustomLinkedList<Integer> {
 *		
 *		protected void solution() {
 *			Node temp = this.head;
 *			
 *			int sum = 0;
 *			while (temp != null) {
 *				sum = sum + (int) temp.getData();
 *				temp = temp.next();
 *			}
 *
 *			System.out.println(sum);
 *		}
 *		
 *		public static void main(String args[]) {
 *			PracticeSoln ll = new PracticeSoln();
 *
 *			ll.add(1);
 *			ll.add(2);
 *			ll.add(3);
 *			ll.add(2);
 *
 *			ll.solution();
 *			System.out.println(ll); // [1, 2, 3, 2]
 *		}
 *
 * }
 *
 *
 * */
public class CustomLinkedList<T> {
	
	protected class Node {
		private T data;
		private Node next;
		
		Node(T data) {
			this.data = data;
			this.next = null;
		}

		Node() { }
		
		public boolean hasNext() {
			return this.next != null;
		}

		public Node setData(T data) {
			this.data = data;
			return this;
		}

		public T getData() {
			return this.data;
		}

		public Node setNext(Node node) {
			this.next = node;
			return this;
		}

		public Node next() {
			return this.next;
		}
	}
	
	
	protected Node head;
	protected int size;
	

	public void add(T data) {
		if (head == null) {
			head = new Node(data);
			size = 1;

		} else {
			Node temp = head;

			while (temp.hasNext()) {
				temp = temp.next();
			}

			temp.setNext(new Node(data));
			size++;
		}
	}

	protected void deleteNextNode(Node node) {
		// Assumes that a node is a valid node.
		// One can send a dummy node with head as its next
		// to delete head
		// Actually you don't need this function
		//
		// But wait please don't delete this
		
		node.setNext(node.next());		
	}

	protected void removeNode(Node node) {

		Node dummy = new Node();
		dummy.setNext(this.head);
		
		Node temp = dummy;
		while (temp != null && temp.next() != node) {
			temp = temp.next();
		}
		
		if (temp != null) {
			temp.setNext(node.next());
		}

		this.head = dummy.next();
	}

	public void removeAt(int index) throws IllegalArgumentException {
		int i = -1;

		Node temp = head;
		while (temp != null) {
				
			if (i == index - 1) {

				if (temp == head) {
					this.deleteNextNode(new Node().setNext(this.head));
				} else {
					this.deleteNextNode(temp);
				}

				return;
			}
			
			temp = temp.next();
		}

		throw new IllegalArgumentException("Invalid Index");
	}

	public String toString() {
			
		StringBuilder text = new StringBuilder("[");

		Node temp = head;
		while (temp != null) {

			if (temp.hasNext()) {
				text.append(temp.getData().toString()+", ");

			} else {
				text.append(temp.getData().toString());
			}

			temp = temp.next();
		}

		text.append("]");
		return text.toString();
	}

}