数据库（极简版）用list的，增，删，改

　　//对于处理数据库的方法list，这些要在已经把数据拿出来储存的条件下
        ArrayList<Snose> snoseArr=new ArrayList<>();//;链接相应的类，new一个
        ArrayList<Courses> courseArr=new ArrayList<>();
        ArrayList<Students> studentArr=new ArrayList<>();
        while (resultSet.next()) {//对一个表进行因此查获
          Snose snose=new Snose();
           snose.setSno(resultSet.getString("sno"));
           snose.setCsno(resultSet.getString("csno"));
           snose.setScore(resultSet.getDouble("score"));
           snoseArr.add(snose);
        }

        preparedStatement = connection.prepareStatement("select * from courses");
        resultSet = preparedStatement.executeQuery();
        resultSet.last();
        while (resultSet.next()){
            Courses courses=new Courses();
            courses.setCsno(resultSet.getString("csno"));
            courses.setCourse(resultSet.getString("course"));
            courseArr.add(courses);
        }

        preparedStatement= connection.prepareStatement("select * from students");
        resultSet = preparedStatement.executeQuery();
        resultSet.last();
        while (resultSet.next()){
            Students student=new Students();
           student.setName(resultSet.getString("name"));
           student.setSno(resultSet.getString("sno"));
           student.setAcademy(resultSet.getString("academy"));
           student.setSex(resultSet.getString("sex"));
           student.setConnect(resultSet.getInt("connect"));
           studentArr.add(student);
        }
        preparedStatement.close();
        resultSet.close();
        Scanner in=new Scanner(System.in);
        //增加
        snoseArr.add(new Snose("202030133010","2020111",89));
        //删除
        System.out.println("请输入要删除的学生学号：");
        String delSno=in.nextLine();
        for(int i=0;i<snoseArr.size();i++){//删除成绩所在类表数据
            if(delSno.equals(snoseArr.get(i).getSno())){
                snoseArr.remove(i);
            }
        }
        for(int i=0;i<snoseArr.size();i++){//删除学生信息所在数据表
            if(delSno.equals(studentArr.get(i).getSno())){
                studentArr.remove(i);
            }
        }
        //修改
        System.out.println("请输入要删除的学生学号：");
        String reSno=in.nextLine();
        System.out.println("请输入要修改的课程号：");
        String reCsno=in.nextLine();
        System.out.println("请输入要修改的成绩：");
        double reScore=in.nextDouble();
        for(int i=0;i<snoseArr.size();i++){
            if(reSno.equals(snoseArr.get(i).getSno())&&reCsno.equals(snoseArr.get(i).getCsno())){//找到对应的成绩
                snoseArr.get(i).setScore(reScore);//修改成绩
                System.out.println("修改结果："+snoseArr.get(i).getScore());//检测修改结果
            }
        }