CustomLinkedList.java

package dataStructure;

public class CustomLinkedList<E> {
	// Linked List Node
	private CustomNode<E> head; // head node
	private CustomNode<E> tail; // tail node
	private int size;
	
	public int size() {
		return size;
	}
	
	public CustomNode<E> get(int index) {
		if (index < 0 || index >= size) throw new IndexOutOfBoundsException();
		
		CustomNode<E> x = head;
		
		for (int i=0;i<index;++i) x = x.next;
		
		return x;
	}
	
	public void addFirst(E value) {
		
		// Create a new node with given data
		CustomNode<E> nn = new CustomNode<E>(value);
		nn.next = head; // new node points to the head node
		head = nn; // the new node becomes the head
		size++; // increment the size
		
		// if there's only one node in the linked list, head and tail should be same.
		if (head.next == null) tail = head;
	}
	
	public void add(E value) {
		addLast(value);
		return;
	}
	
	public void addLast(E value) {
		CustomNode<E> nn = new CustomNode<E>(value);
		
		if (size == 0) {
			addFirst(value);
			return;
		}
		
		tail.next = nn;
		nn = tail;
		size++;
	}
	
	public void add(int index, E value) {
		
		if (index < 0 || index > size) throw new IndexOutOfBoundsException();
		
		if (index == 0) {
			addFirst(value);
			return;
		}
		
		if (index == size) {
			addLast(value);
			return;
		}
		
		// get the prev point at the index
		CustomNode<E> prev = get(index-1);
		CustomNode<E> next = prev.next;
		CustomNode<E> nn = new CustomNode(value);
		
		// Unlink the next node from the prev
		prev.next = null;
		// prev points to the new node
		prev.next = nn;
		// new node points to the next node
		nn.next = next;
		size++;
	}
	
}