///
///<summary>The add method adds given {@link CacheNode} type input cacheNode to the beginning of the doubly
/// {@link java.util.LinkedList}. First it sets cacheNode's previous node as null and cacheNode's next node as
/// head node. If head node is not null then it assigns cacheNode's previous node as head node and if tail is
/// null then it assigns cacheNode as tail.</summary>
///
///<param name="cacheNode"> {@link CacheNode} type input to add to the doubly {@link java.util.LinkedList}.</param>
///
public void Add(CacheNode <TKey, TData> cacheNode)
{
cacheNode.SetPrevious(null);
cacheNode.SetNext(_head);
_head?.SetPrevious(cacheNode);
_head = cacheNode;
if (_tail == null)
{
_tail = cacheNode;
}
}