/*
 * class ObjectLinkedListInterface
 * 
 * Created on Jun 4, 2007
 * 
 * by Donald Yessick
 */
/**
 * @author Donald Yessick
 *
 */
public interface CS220_LinkedList_Interface {
	/**
	 * isEmpty returns the lists status
	 * @return true if the list has no objects
	 */
	boolean isEmpty();
	
	/**
	 * append adds object to tail end of a list
	 * @param object to be added to list
	 */
	void append(Object object);
	
	/**
	 * prepend adds object to head of a list
	 * @param object to be appended to list
	 */
	void prepend(Object object);
	
	/**
	 * insert object to middle of list
	 * @param object to be inserted
	 * @param index number of preceeding items
	 */
	void insert(Object object, int index);
	
	/**
	 * getCount returns the size of the list
	 * @return a count of the objects in the list
	 */
	int getCount();
	
	/**
	 * removeHead deletes the head item in the list
	 * @return the deleted object
	 */
	Object removeHead();
	
	/**
	 * removeTail deletes object from tail end of the list 
	 * @return the deleted object or null if empty
	 */
	Object removeTail();
	
	/**
	 * removeIndex deletes the item in the list indicated by position index
	 * @param index number of objects preceeding targetr
	 * @return deleted object or null
	 */
	Object removeIndex(int index);
	
	/**
	 * retrieve fetches the  item indcated by index
	 * @param index number of objects preceeding target object
	 * @return target object or null
	 */
	Object retrieve(int index);
	
	/**
	 * peekHead fetches object at head of list
	 * @return target object or null
	 */
	Object peekHead();
	
	/**
	 * peekTail fetches object at tail end of list
	 * @return target object or null
	 */
	Object peekTail();
	/**
	 * visit each element using the visitor design pattern
	 * visit
	 * @param v the visitor implementing a visit(object) method
	 */
	void visit(CS220_Visitor_Interface v);

}