nl: item returns this node 's item . if this node is invalid , throws an exception . concode_field_sep Object item concode_elem_sep List myList concode_field_sep ListNode next concode_elem_sep ListNode prev concode_elem_sep boolean isValidNode concode_elem_sep void setItem concode_elem_sep void insertAfter concode_elem_sep void remove concode_elem_sep void insertBefore
code: Object function ( ) { if ( ! isValidNode ( ) ) { throw new InvalidNodeException ( ) ; } return item ; }