如果循环导致意外输出时，内部内部切换的语句会导致

Question

肯定有更实用的方式编写以下代码的方法。但是我真的想了解为什么它正在打印行 “写下行动（购买，填充，剩下，退出）：“在采取行动后两次。 在询问用户输入的输出后，对我来说没有任何意义，那么如何打印两次？ 这发生在动作“购买”和“填充”之后发生，但不要使用“ take”＆amp;＆amp; “其余的”。我想念什么？ （只需运行代码，您就会明白我的意思！）

import java.util.Scanner;

    public class Main {
    
        private static void printMachineState(int water, int milk, int beans, int cups, int money) {
            System.out.printf("The coffee machine has:\n%d ml of water\n%d ml of milk\n%d g of coffee beans\n%d disposable cups\n$%d of money\n", water, milk, beans, cups, money);
        }
    
    
        public static void main(String[] args) {
            Scanner sc = new Scanner(System.in);
    
            int water = 400;
            int milk = 540;
            int beans = 120;
            int cups = 9;
            int money = 550;
            int coffeeEnum;
            boolean exitFlag = false;
    
            while (!exitFlag) {
                System.out.println("Write action (buy, fill, take, remaining, exit):");
                String input = sc.nextLine();
    
                switch (input) {
                    case "buy":
                        System.out.println("What do you want to buy? 1 - espresso, 2 - latte, 3 -cappuccino");
                        coffeeEnum = sc.nextInt();
    
                        if (coffeeEnum == 1) {
                            if (water < 250) {
                                System.out.println("Sorry, not enough water!");
                                break;
                            }
                            if (beans < 16) {
                                System.out.println("Sorry, not enough beans!");
                                break;
                            }
                            if (cups == 0) {
                                System.out.println("Sorry, not enough cups!");
                                break;
                            }
                            water -= 250;
                            beans -= 16;
                            money += 4;
                            cups--;
                            System.out.println("I have enough resources, making you a coffee!");
                            break;
                        }
    
                        if (coffeeEnum == 2) {
                            if (water < 350) {
                                System.out.println("Sorry, not enough water!");
                                break;
                            }
                            if (milk < 75) {
                                System.out.println("Sorry, not enough milk!");
                                break;
                            }
                            if (beans < 20) {
                                System.out.println("Sorry, not enough beans!");
                                break;
                            }
                            if (cups <= 0) {
                                System.out.println("Sorry, not enough cups!");
                                break;
                            }
                            water -= 350;
                            milk -= 75;
                            beans -= 20;
                            money += 7;
                            cups--;
                            System.out.println("I have enough resources, making you a coffee!");
                            break;
                        }
    
                        if (coffeeEnum == 3) {
                            if (water < 200) {
                                System.out.println("Sorry, not enough water!");
                                break;
                            }
                            if (milk < 100) {
                                System.out.println("Sorry, not enough milk!");
                                break;
                            }
                            if (beans < 12) {
                                System.out.println("Sorry, not enough beans!");
                                break;
                            }
                            if (cups == 0) {
                                System.out.println("Sorry, not enough cups!");
                                break;
                            }
                            water -= 200;
                            milk -= 100;
                            beans -= 12;
                            money += 6;
                            cups--;
                            System.out.println("I have enough resources, making you a coffee!");
                            break;
                        }
                    case "fill":
                        System.out.println("Write how many ml of water you want to add:");
                        water += sc.nextInt();
                        System.out.println("Write how many ml of milk you want to add:");
                        milk += sc.nextInt();
                        System.out.println("Write how many grams of coffee beans you want to add:");
                        beans += sc.nextInt();
                        System.out.println("Write how many disposable cups of coffee you want to add:");
                        cups += sc.nextInt();
                        printMachineState(water, milk, beans, cups, money);
                        break;
                    case "take":
                        System.out.printf("I gave you %d\n", money);
                        money = 0;
                        break;
                    case "remaining":
                        printMachineState(water, milk, beans, cups, money);
                        break;
                    case "exit":
                        exitFlag = true;
                        break;
                    default:
                        break;
                }
            }
    
        }
    }

Answer 1

扫描仪方法nextInt（）仅接收数字，但在此之后被送入扫描仪的新线。因此，nextline（）被称为nextline（）获取newline并跳到默认开关情况，然后开始循环并再次打印行。

一个简单快速的修复方法是将扫描仪sc的实例化移至WARE循环，以便每次循环时，都会制作一个新的“清洁”空扫描仪。