SinglyLinkedList.java

public class SinglyLinkedList<E> {
	//--------nested node class------
	private static class Node<E>{
		private E element;	//reference to the element stored at this node
		private Node<E> next;	//reference to the subsequent node in the kist
		public Node(E e,Node<E> n){
			element = e;
			next = n;
		}
		public E getElement(){
			return element;
		}
		public Node<E> getNext(){	
			return next;
		}
		public void setNext(Node<E> n){
			next = n;
		}
	}
	//---------end of the nested class-----
	
	//instance variables of the SinglyLinledList
	private Node<E> head = null;
	private Node<E> tail = null;
	private int size = 0;
	public SinglyLinkedList(){}
	//access methods
	public int size(){
		return size;
	}
	public boolean isEmpty(){
		return size == 0;
	}
	public E first(){
		if(isEmpty())
			return null;
		return head.getElement();
	}
	public E last(){
		if(isEmpty()) return null;
		return tail.getElement();
	}
	public void addFirst(E e){
		head = new Node<>(e,head);
		if(size == 0 )
			tail = head;
		size++;
	}
	public void addLast(E e){
		Node<E> newest = new Node<>(e,null);
		if(isEmpty()){
			head = newest;
		}
		else
			tail.setNext(newest);
		tail=newest;
	size++;
	}
	public E removeFirst(){
		if(isEmpty()) return null;
		E answer = head.getElement();
		head = head.getNext();
		size--;
		if(size == 0){
			tail = null;
		}
		return answer;
	}
	
	
	
	
}