front returns the node at the front of this dlist . if dlist is empty , return null . do not return the sentinel under any circumstances ! concode_field_sep DListNode head concode_elem_sep int size concode_elem_sep int x concode_field_sep DListNode next concode_elem_sep DListNode prev concode_elem_sep boolean isEmpty concode_elem_sep int length concode_elem_sep void insertFront concode_elem_sep DListNode back concode_elem_sep void main concode_elem_sep void insertBack concode_elem_sep void insertAfter concode_elem_sep void remove concode_elem_sep void insertBefore concode_elem_sep DListNode newNode concode_elem_sep String toString
DListNode function ( ) { if ( size == 0 ) { return null ; } else { return head . next ; } }