boolean function ( ) { return first == null ; }
is the stack empty ? concode_field_sep Node next concode_elem_sep Item item concode_elem_sep int N concode_elem_sep Node first concode_elem_sep Node current concode_field_sep Item pop concode_elem_sep Item next concode_elem_sep Iterator<Item> iterator concode_elem_sep int size concode_elem_sep String toString concode_elem_sep boolean hasNext concode_elem_sep void main concode_elem_sep boolean check concode_elem_sep void push concode_elem_sep void remove concode_elem_sep Item peek