完成任务后返回主菜单方法

Question

我的所有代码都可以在我的控制台上正常运行。我能够完美地选择、更新、删除和查看所有内容。但是，在用户完成任何任务后，我希望从 mainMenuOptions() 获得原始主菜单，以便从头开始。目前它正在将我循环回到accountsTable() 方法。有什么想法吗？

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Scanner;
import java.sql.PreparedStatement;
import java.sql.*;
import static java.lang.System.out;

public class Menu {

    static boolean exit;
    static final String DB_URL = "jdbc:mysql://localhost:3306/chocolatemilk_review";
    static final String USER = "root";
    static final String PASS = "";

    private static Connection connection = null;
    static Scanner input = new Scanner(System.in);

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

        mainMenuOptions();
        input.close();

    }

    public static Connection connect() throws SQLException {

        return DriverManager.getConnection(DB_URL, USER, PASS);

    }

    public static void mainMenuOptions() {

        int numEntered;

        try { 

            do {

                out.println("Choconnoisseur Menu");
                out.println();
                out.println("Enter 1 for Accounts ");
                out.println("Enter 2 for Merchandise ");
                out.println("Enter 3 for Merchsales ");
                out.println("Enter 4 for Product Reviews ");
                out.println("Enter 5 to Exit"); 
                out.println();
                out.println("Enter number here: ");
                numEntered = input.nextInt(); 
                input.nextLine();

                switch(numEntered) {
                case 1: 
                    accountsTable();
                    out.println("Account Options");
                    break;
                case 2: 
                    merchandiseTable();
                    out.println("Merchandise Options");
                    out.println();
                    break;
                case 3: 
                    merchsalesTable();
                    out.println("Merchsales Options");
                    out.println();
                    break;
                case 4: 
                    productReviewsTable();
                    out.println("Product Reviews Options");
                    out.println();
                    break;
                case 5: 
                    exit = true;
                    out.println("Have a nice day! "); 
                    out.println();
                    break;
                default:
                    out.println("Invalid entry, choose from one the options listed.");
                    out.println();
                    break;
                }

            }
            while (numEntered != 5);  
        } 
        catch (Exception e) { 
            out.println("Invalid entry");
            e.printStackTrace();
        }
    }

    public static void accountsTable() throws SQLException  {

        int accountOpts;

        try { 

            do {

                out.println("Accounts Table");
                out.println();
                out.println("Enter 1 for Add Account");
                out.println("Enter 2 for Edit Account");
                out.println("Enter 3 for  Remove Account");
                out.println("Enter 4 for View Account");
                out.println("Enter 5 back to Main Menu"); 
                out.println();
                out.println("Enter number here: ");
                accountOpts = input.nextInt();
                input.nextLine();
                out.println();

                switch (accountOpts) {
                case 1: 
                    out.println("Add Accounts");
                    insertInfo();

                    break;
                case 2: 
                    out.println("Edit Accounts");
                    updateAccounts();
                    out.println();
                    break;
                case 3: 
                    out.println("Remove Accounts");
                    deleteAccounts(); 
                    out.println();
                    break;
                case 4: 
                    out.println("View Accounts");
                    selectAccounts();    
                    out.println();
                    break;
                case 5: 
                    out.println("Back to Main Menu ");
                    out.println();
                    break; 
                default:
                    out.println("Invalid entry, choose from one the options listed.");
                    out.println();
                    break;
                }
            }
            while (accountOpts != 5);  
        } 
        catch (Exception e) { 
            out.println("Invalid entry");
            e.printStackTrace();
        }
    }

    private static void insertInfo() throws SQLException   {

        out.println();

        connection = connect();

        String SQL = "INSERT INTO Accounts(last, first, address, city, state, email) VALUES(?,?,?,?,?,?)";
        PreparedStatement prepInsertStatement = connection.prepareStatement(SQL);

        out.println("Enter last name: ");
        String lastName = input.nextLine();
        prepInsertStatement.setString(1, lastName);

        out.println("Enter first name: ");
        String firstName = input.nextLine();
        prepInsertStatement.setString(2, firstName);

        out.println("Enter address: ");
        String address = input.nextLine();
        prepInsertStatement.setString(3, address);

        out.println("Enter city: ");
        String city = input.nextLine();
        prepInsertStatement.setString(4,  city);

        out.println("Enter state: ");
        String state = input.nextLine();
        prepInsertStatement.setString(5, state);

        out.println("Enter email: ");
        String email = input.nextLine();
        prepInsertStatement.setString(6, email);

        int result = prepInsertStatement.executeUpdate();
        if(result == 1)
            out.println("Account added. ");
        else
            out.println("Account not added. ");
        out.println();

    }

    private static void updateAccounts() throws SQLException {

        out.println();

        connection = connect();

        String SQL = "UPDATE Accounts SET last = ?, first = ?, address = ?, city = ?, state = ?, "
                + "email = ? WHERE account_id = ?";
        PreparedStatement prepUpdateStatement = connection.prepareStatement(SQL);

        out.println("Enter Account to Update: ");
        int accountUpdate = input.nextInt();
        prepUpdateStatement.setInt(7, accountUpdate);
        //how come when int comes first both update last and first come at same time in console?

        out.println("Update last name: ");
        String lastName = input.nextLine();
        prepUpdateStatement.setString(1, lastName);

        out.println("Update first name: ");
        String firstName = input.nextLine();
        prepUpdateStatement.setString(2, firstName);

        out.println("Update address: ");
        String address = input.nextLine();
        prepUpdateStatement.setString(3, address);

        out.println("Update city: ");
        String city = input.nextLine();
        prepUpdateStatement.setString(4,  city);

        out.println("Update state: ");
        String state = input.nextLine();
        prepUpdateStatement.setString(5, state);

        out.println("Update email: ");
        String email = input.nextLine();
        prepUpdateStatement.setString(6, email);

        int updateRow = prepUpdateStatement.executeUpdate();
        if(updateRow == 1)
            out.println("Update Successful. ");
        else
            out.println("Update Not Successful. ");

        //why 1 for updateRow == 1?

    }

    private static void deleteAccounts() throws SQLException  {

        out.println();

        connection = connect();

        String SQL = "DELETE FROM Accounts WHERE account_id = ? ";
        PreparedStatement prepDeleteStatement = connection.prepareStatement(SQL);

        out.println("Enter an account_id to remove account: "); 
        int enterAccount = input.nextInt();
        prepDeleteStatement.setInt(1, enterAccount);

        int deleteAccount = prepDeleteStatement.executeUpdate();
        if(deleteAccount == 1)
            out.println("Account deleted. ");
        else
            out.println("Account doesn't exist or not deleted. ");


    }

    private static void selectAccounts() throws SQLException  {

        out.println();

        connection = connect();

        String SQL = "SELECT * FROM accounts WHERE account_id = ? ";

        PreparedStatement prepSelectStatement = connection.prepareStatement(SQL);    

        out.println("Enter account ID to review account: ");
        int accountId = input.nextInt();
        prepSelectStatement.setInt(1, accountId);
        out.println();

        ResultSet rsViewAccount = prepSelectStatement.executeQuery();
        if(!rsViewAccount.isBeforeFirst()) {

            out.println("No rows in Accounts");
        }

        else {

            while (rsViewAccount.next()) {

                out.println("Enter 1 for last name: " + rsViewAccount.getString(2));
                out.println("Enter 2 for first name: " + rsViewAccount.getString(3));
                out.println("Enter 3 for address: " + rsViewAccount.getString(4));
                out.println("Enter 4 for city: " + rsViewAccount.getString(5));
                out.println("Enter 5 for state: " + rsViewAccount.getString(6));
                out.println("Enter 6 email: " + rsViewAccount.getString(7));

            }
        }
    }

Answer 1

如果代码将您循环到accountsTable 方法，则您似乎输入了“1”。
现在假设您执行了一次，浏览 accountTable 然后返回，您会期望显示菜单。我怀疑这确实正在发生。

但随后您的代码立即认为再次输入了“1”。我相信无论出于何种原因，它仍然在输入缓冲区中。

为了摆脱这个问题，请在显示菜单之后和读取输入之前清空缓冲区。查看如何清除 Java 中的扫描仪缓冲区？

编辑：在你的accountsTable方法中我可以看到你已经尝试过类似的事情了。在主菜单级别执行相同的操作。