java - 如何在菜单循环后执行打印语句然后返回主菜单？

Question

在 printMenuItems 方法中，程序应在用户选择要添加到购物车中的项目时循环。当用户位于项目菜单中时，程序应在底部显示“您当前的总计为:$”，直到用户选择返回主菜单。返回主菜单后，程序底部应显示“您的应付款总额为:$”。我目前在程序返回主菜单之前执行“您的总应付款为:$”语句，当用户返回时，该语句将“您的总应付款为”语句置于主菜单上方。我正在尝试弄清楚如何将该语句放在主菜单下方

import java.util.Scanner;
public class Homework1 {

    static double userTotal = 0;
    static double userCredit = 100;
    static double [] menuPrices = {19.99, 29.49, 15.79, 24.99, 24.99};
    static Scanner myScanner = new Scanner(System.in);

    public static int printMainMenu() {
        System.out.println("Please select a menu item from the list below: \n" +
                "1 - View item menu \n" +
                "2 - Pay total due \n" +
                "3 - Add $5 in credit \n" +
                "4 - Clear order");

        int userChoice = myScanner.nextInt();
        if (userChoice > 0 && userChoice < 5) {
            return userChoice;
        }
        else {
            System.out.println("Please enter a valid option!");
            printMainMenu();
        }
        return 0;
    }

    public static double printMenuItems(double userTotal) {
        System.out.println("What would you like to add to your order? \n" +
                "(1) Toaster: $19.99 \n" +
                "(2) Coffee maker: $24.49 \n" +
                "(3) Waffle maker: $15.79 \n" +
                "(4) Blender: $24.99 \n" +
                "(5) Kettle: $24.99 \n" +
                "(6) Go to the main menu");
        System.out.println("Your current total is: $" + userTotal);
        int menuSelections = myScanner.nextInt();

        if (menuSelections == 1) {
            System.out.println("You have added a Toaster to your order.");
            userTotal += menuPrices[0];
        }
        else if (menuSelections == 2) {
            System.out.println("You have added a Coffee maker to your order.");
            userTotal += menuPrices[1];
        }
        else if (menuSelections == 3) {
            System.out.println("You have added a Waffle maker to your order.");
            userTotal += menuPrices[2];
        }
        else if (menuSelections == 4) {
            System.out.println("You have added a Blender to your order.");
            userTotal += menuPrices[3];
        }
        else if (menuSelections == 5) {
            System.out.println("You have added a Kettle to your order.");
            userTotal += menuPrices[4];
        }
        else if (menuSelections == 6) {
            System.out.println("Your total due is: $" + userTotal); 
            return userTotal;
        }
        else {
            System.out.println("Invalid item number please try again");
        }
        return printMenuItems(userTotal);

    }

    public static boolean payTotalDue(double userTotal) {
        double preTaxTotal = userTotal;
        if (preTaxTotal > 50) {
            preTaxTotal -= (preTaxTotal * 0.2);
            preTaxTotal += (preTaxTotal * 0.085);

            if (preTaxTotal <= userCredit) {
                System.out.println("Thank you! You saved: $" + (userTotal + (userTotal * 0.085) - preTaxTotal) +
                        " Your change is: $" + (userCredit - preTaxTotal));
                System.out.println("Your items will be on their way soon!");

            }
            else {
                System.out.println("Insufficient funds!");
                System.exit(0);
            }

        }
        else {
            preTaxTotal += (preTaxTotal * 0.085);
            System.out.println("Thank you! Your change is: $" + (userCredit - preTaxTotal));
            System.out.println("Your items will be on their way soon!");
        }
        return true;
    }

    public static void main(String[] args) {

        while (true) {
            int mainMenuSelection = printMainMenu();
            if (mainMenuSelection == 1) {
                userTotal = printMenuItems(userTotal);

            }
            else if (mainMenuSelection == 2) {
                if (payTotalDue(userTotal)) {
                    userTotal = 0;
                    break;
                }
            }
            else if (mainMenuSelection == 3) {
                userCredit += 5;
                System.out.println("Credit available: $" + userCredit);
            }
            else if (mainMenuSelection == 4) {
                System.out.println("Current order balance has been cleared. Current due: $0.00");
                userTotal = 0;
            }
        }
    }
}

Answer 1

简单地在集团之下

 public static int printMainMenu() {
    System.out.println("Please select a menu item from the list below: \n" +
            "1 - View item menu \n" +
            "2 - Pay total due \n" +
            "3 - Add $5 in credit \n" +
            "4 - Clear order");

添加

if ( userTotal > 0 ) {
            System.out.println("Your total due is: $" + userTotal);
        }

并从 block 中删除打印

 else if (menuSelections == 6) {
        System.out.println("Your total due is: $" + userTotal); 
        return userTotal;
    }

此外，使用 java switch 而不是许多 if else 会更好/更简单

 switch (myScanner.nextInt()) {
            case 1:
                System.out.println("You have added a Toaster to your order.");
                userTotal += menuPrices[0];
                break;
            case 2:
                System.out.println("You have added a Coffee to your order.");
                userTotal += menuPrices[0];
                break;
            case 3: (continue with same..)
            default:
                System.out.println("Invalid item number please try again");
        }

根据问题，一旦您可以使用这个简单的代码片段，我如何运行代码打印输出

static boolean doOnce = true; //put this somewhere to be executed once , like begin of your program
...
if ( doOnce ) {
        System.out.println("Your total due is: $" + userTotal);
        doOnce = false;
}