ToDoList

import java.sql.*;
import java.util.ArrayList;
import java.util.Scanner;

public class ToDo {

    private static final String URL = "jdbc:mysql://localhost:3306/ToDo?useUnicode=true&characterEncoding=utf8 ";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "";

    private static ResultSet result;
    private static Connection con;
    private static PreparedStatement prstmt;

    private static void add(String task) throws SQLException {
        prstmt = con.prepareStatement("insert into Tasks (Task) values(?)");
        prstmt.setString(1, task);
        prstmt.executeUpdate();

        prstmt = con.prepareStatement("select id from Tasks where Task = ?");
        prstmt.setString(1, task);
        result = prstmt.executeQuery();
        result.next();
        System.out.println("Task - " + task + " added by id " + result.getInt("id"));
    }

    private static void show(String buf) throws SQLException {
        if (buf.equals("")) {
            prstmt = con.prepareStatement("select id from Tasks");
            ResultSet result1 = prstmt.executeQuery();
            int tmp;
            ArrayList<Integer> id = new ArrayList<>();
            while (result1.next()){
                tmp = result1.getInt("id");
                id.add(tmp);
                prstmt = con.prepareStatement("select Task from Tasks where id = ?");
                prstmt.setInt(1, tmp);
                result = prstmt.executeQuery();
                result.next();
                System.out.println(tmp + ": " + result.getString("Task"));

            }
            if (id.size() == 0){
                System.out.println("You have not added any tasks");
                return;
            }
        }else{
            try{
                prstmt = con.prepareStatement("select task from Tasks where id = ?");
                prstmt.setInt(1, Integer.parseInt(buf));
                result = prstmt.executeQuery();
                result.next();
                System.out.println(result.getString("Task"));
            }catch (SQLException e){
                System.out.println("Task № " + buf + " does not exist");
            }
        }
    }

    private static void del(String buf) {
        try {
            prstmt = con.prepareStatement("select task from Tasks where id = ?");
            prstmt.setInt(1, Integer.parseInt(buf));
            result = prstmt.executeQuery();
            result.next();
            result.getString("Task");
            prstmt = con.prepareStatement("delete from Tasks where id = ?");
            prstmt.setInt(1, Integer.parseInt(buf));
            prstmt.executeUpdate();
            System.out.println("Task № " + buf + " deleted");
        }catch (SQLException e) {
            System.out.println("Task № " + buf + " does not exist");
        }catch (NumberFormatException e){
            System.out.println("Incorrect task number");
        }
    }

    private static void edit(String buf){
        Scanner sc = new Scanner(System.in);
        try {
            prstmt = con.prepareStatement("select task from Tasks where id = ?");
            prstmt.setInt(1, Integer.parseInt(buf));
            result = prstmt.executeQuery();
            result.next();
            System.out.println("task to change - " + result.getString("Task"));
            prstmt = con.prepareStatement("update Tasks set task  = ? where id = ?");
            String tmp = sc.nextLine();
            prstmt.setString(1, tmp);
            prstmt.setInt(2, Integer.parseInt(buf));
            prstmt.executeUpdate();
            System.out.println("Task " + Integer.parseInt(buf) + " changed to " + tmp);
        } catch (SQLException e) {
            System.out.println("Task № " + buf + " does not exist");
        }catch (NumberFormatException e){
            System.out.println("Incorrect task number");
        }
    }

    public static void main(String[] args) throws SQLException {
        Driver driver;

        try   {
            driver = new com.mysql.cj.jdbc.Driver();
            DriverManager.registerDriver(driver);
        }
        catch (SQLException e1) {
            System.out.println("Oops");
        }

        try{
            con = DriverManager.getConnection(URL, USERNAME, PASSWORD);
        } catch (SQLException e) {
            e.printStackTrace();
        }

        Scanner sc = new Scanner(System.in);
        while (true){
            StringBuilder buf = new StringBuilder();
            String[] command = sc.nextLine().split(" ");
            for (int i = 1; i < command.length; i++){
                if (i + 1 == command.length){
                    buf.append(command[i]);
                }else{
                    buf.append(command[i]).append(" ");
                }
            }
            switch (command[0].toUpperCase()){
                case "ADD":
                    add(buf.toString());
                    break;
                case "SHOW":
                    show(buf.toString());
                    break;
                case "DEL":
                    del(buf.toString());
                    break;
                case "EDIT":
                    edit(buf.toString());
                    break;
                case "EXIT":
                    return;
                default:
                    System.out.println("incorrect input");
                    break;
            }
        }
    }
}