question: isempty returns true if this queue is empty , false otherwise . concode_field_sep SListNode head concode_elem_sep int size concode_elem_sep SListNode tail concode_field_sep void enqueue concode_elem_sep Object nth concode_elem_sep int size concode_elem_sep Object dequeue concode_elem_sep String toString concode_elem_sep Object front concode_elem_sep void append
target: boolean function ( ) { return size == 0 ; }