returns true if this queue is empty . concode_field_sep Node<Item> next concode_elem_sep Item item concode_elem_sep Node<Item> current concode_elem_sep Node<Item> last concode_elem_sep Node<Item> first concode_elem_sep int N concode_field_sep Item next concode_elem_sep void enqueue concode_elem_sep Iterator<Item> iterator concode_elem_sep int size concode_elem_sep Item dequeue concode_elem_sep String toString concode_elem_sep boolean hasNext concode_elem_sep void main concode_elem_sep void remove concode_elem_sep Item peek
boolean function ( ) { return first == null ; }