Java多方法调用问题：第二个方法无法运行的求助咨询

你的代码核心问题是定义了两个public static void main(String[] args)方法，Java程序只能有一个入口方法，这会直接导致编译失败，使得oneRoundOfOrders方法根本无法执行。下面是修复后的完整代码及关键说明：

修复后的完整代码 #

// Author : Maya Strickland
//Project Name : MCC Grub & Grill
// Date: 09/27/2022
import java.util.Scanner;

class Main {
  
    // 菜单商品价格常量
    static final double smallPizza = 8.99;
    static final double mediumPizza = 11.99;
    static final double largePizza = 14.99;
    static final double veggieBurger = 5.99;
    static final double grilledChickenSandwich = 6.99;
    static final double hamburgerSandwich = 7.99;
    static final double macAndCheese = 2.49;
    static final double handCutFries = 2.75;
    static final double onionRings = 2.99;
    static final double foodTaxRate = 4.125;
    static double total = 0;
    static Scanner input; // 全局Scanner，避免重复创建

    // 显示菜单的方法
    static void showMenu() {  
        System.out.println("");
        System.out.println("Welcome to MCC Grub and Grill!");
        System.out.println("");
        System.out.println("Here is a list of our current menu items: ");
        System.out.println("");
        System.out.println("Entrees: ");
        System.out.println("1. Small Pizza - Perfect size pizza for just one.....$8.99");
        System.out.println("2. Medium Pizza - A pizza big enough to share, or not.....$11.99");
        System.out.println("3. Large Pizza - A pizza big enough for the whole family!.....$14.99");
        System.out.println("4. Veggie Burger - A black bean burger with Tomato, Mayo, Lettuce, and PepperJack Cheese. All grilled on a panini press.....$5.99");
        System.out.println("5. Grilled Chicken Sandwich - Grilled Chicken topped with Tomato, Mayo, Lettuce, PepperJack Cheese. All grilled on a panini press.....$6.99");
        System.out.println("6. Hamburger- Classic 100% beef patty with Tomato, Mayo, Lettuce and PepperJack Cheese. All grilled on a panini press.....$7.99");
        System.out.println("");

        System.out.println("Sides: ");
        System.out.println("7. Mac and Cheese - Not your momma's mac! Spicy 3 Cheese Mac made with Red Pepper Flakes. Beware the spice!.....$2.49");
        System.out.println("8. Hand-Cut Fries - Crisp, golden fries deep fried in peanut oil.....$2.75");
        System.out.println("9. Onion Rings - Crisp, golden rings of onion deep fried in peanut oil.....$2.99");
        System.out.println("");
    }

    // 处理单次下单的方法
    static boolean processOrder() {
        System.out.println("Please enter the menu number of the food you would like to order or 0 to stop ordering");
        int menuItem = input.nextInt();
        
        switch (menuItem) {
            case 0:
                // 计算含税总价并显示
                double tax = total * (foodTaxRate / 100);
                double finalTotal = total + tax;
                System.out.printf("当前未税总价: $%.2f\n", total);
                System.out.printf("税费: $%.2f\n", tax);
                System.out.printf("最终总价: $%.2f\n", finalTotal);
                return false; // 返回false表示结束下单
                
            case 1:
                System.out.println("You've chosen small pizza! A perfect size pizza for just one! " + "$" + smallPizza);
                total += smallPizza;
                break;
             
            case 2:
                System.out.println("You've chosen medium pizza! A pizza big enough to share...or not " + "$" + mediumPizza);
                total += mediumPizza;
                break;
            
            case 3:
                System.out.println("You've chosen large pizza. A pizza big enough for the whole family! " + "$" + largePizza);
                total += largePizza;
                break;
            
            case 4:  
                System.out.println ("You've chosen Veggie Burger! A black bean burger with Tomato, Mayo, Lettuce, and PepperJack Cheese. All grilled on a panini press. " + "$" + veggieBurger);
                total += veggieBurger;
                break;
            
            case 5:
                System.out.println("You've chosen Grilled Chicken Sandwich! Grilled Chicken topped with Tomato, Mayo, Lettuce, PepperJack Cheese. All grilled on a panini press " + "$" + grilledChickenSandwich);
                total += grilledChickenSandwich;
                break;
           
            case 6:
                System.out.println("You've chosen a Hamburger! Classic 100% beef patty with Tomato, Mayo, Lettuce and PepperJack Cheese. All grilled on a panini press " + "$" + hamburgerSandwich);
                total += hamburgerSandwich;
                break;
            
            case 7:
                System.out.println("You've chosen Mac and Cheese! Not your momma's mac! Spicy 3 Cheese Mac made with Red Pepper Flakes. Beware the spice! " + "$" + macAndCheese);
                total += macAndCheese;
                break;
            
            case 8:
                System.out.println("You've chosen Hand Cut Fries! Crisp, golden fries deep fried in peanut oil " + "$" + handCutFries);
                total += handCutFries;
                break;
                
            case 9:
                System.out.println("You've chosen Onion Rings! Crisp, golden rings of onion deep fried in peanut oil " + "$" + onionRings);
                total += onionRings;
                break; 
            default:
                System.out.println("Please try again");
        }
        return true; // 返回true表示继续下单
    }

    // 唯一的程序入口main方法
    public static void main(String[] args) {
        input = new Scanner(System.in); // 初始化Scanner
        showMenu(); // 先显示菜单
        
        // 循环处理下单，直到用户输入0
        while (processOrder()) {
            // 每次下单后显示当前总价
            System.out.printf("当前未税总价: $%.2f\n\n", total);
        }
        
        input.close(); // 关闭Scanner
    }
}

关键修改说明 #

1. 移除重复的main方法：Java程序只能有一个入口方法，将两个main的逻辑合并，先调用菜单显示，再循环处理下单。
2. 优化方法命名：把myMethod改为showMenu，oneRoundOfOrders改为processOrder，让方法名更具语义性，提升代码可读性。
3. 统一Scanner实例：将Scanner定义为类静态成员，避免每次下单都重复创建对象，节省资源。
4. 增加循环下单逻辑：让processOrder返回布尔值，在main中用while循环实现多次下单，直到用户输入0结束。
5. 完善总价计算：用户输入0时自动计算税费和最终总价，完善点餐流程。
6. 规范类名：Java类名首字母需大写，将class main改为class Main，符合编码规范。

Java多方法使用核心要点 #

• 职责单一：每个方法只负责一件事，比如showMenu仅显示菜单，processOrder仅处理单次下单，代码更清晰易维护。
• 调用顺序合理：在main入口方法中按业务逻辑依次调用其他方法，比如先展示菜单再处理下单。
• 静态方法配合：main是静态方法，调用的其他方法需为静态（或创建类实例调用非静态方法），静态变量可用于共享数据（如total）。
• 避免重复代码：不要重复定义相同方法，也不要在多个方法中重复创建相同对象。

内容的提问来源于stack exchange，提问作者Maya Strickland