LinkedList.java

public class LinkedList 
{
   private Node first;
   private Node last;
   private Node current; 
   
	public LinkedList()
	{
		first = null;
      last = null;
      current = null;  
	}
	
	public boolean isEmpty()
   {	return (first == null);	}   
	
	public void insertAtFront(Object insertItem)
   {
   	Node newNode = new Node(insertItem);
       
      if (isEmpty())
      {
      	first = newNode;
         last = newNode;
      }
      
		else
      {
          newNode.next = first;
          first = newNode;
      }
    }
	 
	 public void insertAtBack(Object insertItem)
    {
        Node newNode = new Node(insertItem);
        
        if(isEmpty())
        {
            first = newNode;
            last = newNode;
        }
        else
        {
            last.next = newNode;
            last = newNode;
        }
    }
	 
	 public Object removeFromFront()
    {
        Object removeItem = null;
        
        if(isEmpty())
        {
            return removeItem;
        }
        
        removeItem = first.data;
        
		  if(first == last)
     		{
            first = null;
            last = null;
    		}
     		else
           	first = first.next;
           
    return removeItem;
 	}
	
	public Object removeFromBack()
   {
   	Object removeItem = null;
        
      if(isEmpty())
      {
      	return removeItem;
      }
        
      removeItem = last.data;
		  
		if (first == last)
      {
         first = null;
         last = null;
      }
      
		else
      {
         current = first;
         while(current.next != last)
         	current = current.next;
         last = current;
         last.next = null;
        }
        
      return removeItem;
 	 }
	 
	 public Object getFirst()
    {
        if(isEmpty())
          return null;
        else
        {
            current = first;
            return current.data;
        }
    }
	 
	 public Object getNext()
   {
        if(current == last)
          return null;
        else
        {
            current = current.next;
            return current.data;
        }
    }
    public int size()
    { 
      Node temp=first;
      int count = 0; 
      while(temp!=null)
      { 
         temp=temp. next;
         count++; 
      }
      return count;
    }
	 
	 	 
}