code: protected void pushFrontEntry(T e) {
          e.setPrev(null);
          e.setNext(head);
          if (head != null) {
              head.setPrev(e);
          } else {
              last = e;
          }
          head = e;
          size++;
      }
docs: Adds an entry at the beginning of the list.
  
  @param e
  the entry to add.