singleton pattern과 list를 활용한 crud 구조 Mainclass.java package main; import java.util.Scanner; import cls.DeleteClass; import cls.InsertClass; import cls.SelectClass; import cls.UpdateClass; public class MainClass { public static void main(String[] args) { Scanner s = new Scanner(System.in); // initialize // loop // release //menu 추가(insert), 삭제(delete), 검색(select), 수정(update) while(true) { System...