Java 当用户输入“错误”时，告诉它

这是我的密码。我真的一直在查看整个过程，但为了我的生命，我无法找出导致代码对我不利的问题在哪里：

import java.util.ArrayList;
import java.util.Scanner;

public class DogGompundTest {
    public static void main(String[] args) {
        boolean dogFound = false;
        boolean toEnd = false;
        Scanner keyboard = new Scanner(System.in);
        ArrayList<Dog> dogRegister = new ArrayList<Dog>();

        //Other dogs in program 
        Dog d2 = new Dog("Mira", "Miniature Schnauzer", 1, 8.0, 0.8);
        dogRegister.add(d2);
        Dog d3 = new Dog("Jack", "Jack Russell", 3, 6.0, 1.8);
        dogRegister.add(d3);
        Dog d4 = new Dog("Charlie", "Pug", 5, 5.0, 2.5);
        dogRegister.add(d4);
        Dog d5 = new Dog("Max", "Dachshund", 9, 5.0, 3.7);
        dogRegister.add(d5);
        Dog d6 = new Dog("Bingo", "Golden Retriever", 5, 12.0, 6.0);
        dogRegister.add(d6);

        System.out.println("Name - Race - Age - Weight - Taillength: " + dogRegister);

        while (toEnd == false) {
            System.out.println(
                "\nWhat would you like to do? \n Press 1 to register a dog. \n Press 2 to get a " +
                    "look at the taillengths of the dogs. \n Press 3 to delete a dog from " +
                    "the register.\n Press 4 to quit.");
            int command = keyboard.nextInt(); //Alternatives stored in "command"
            keyboard.nextLine();
            switch (command) { //Execute chosen command in switch-statement
                case 1: //User registers a dog 
                    Dog d1 = new Dog("", "", 0, 0.0, 0.0);
                    System.out.println("\nPlease enter the dogs name:");
                    String Name = keyboard.next();
                    d1.setName(Name);

                    System.out.println("\nPlease enter the dogs race (in English):");
                    String Race = keyboard.next();
                    d1.setRace(Race);

                    System.out.println("\nPlease enter the dogs age (years):");
                    int age = keyboard.nextInt();
                    d1.setage(age);

                    System.out.println("\nPlease enter the dogs weight in kg:");
                    double weight = keyboard.nextDouble();
                    d1.setweight(weight);

                    dogRegister.add(d1);
                    System.out.println("\n");
                    System.out.println(
                        "\nComplete dog information: " + "\nName: " + Name + "\nRace: " + Race
                            + "\nAge: " + age + "\nWeight: " + weight + " kg");
                    System.out.println(dogRegister);
                    break;
                case 2: //User gets to see the different taillengths of the dogs in the register

                    System.out.println(
                        "\nEnter taillength and all dogs with a greater taillength will be displayed: ");
                    double taillength = keyboard.nextDouble();
                    for (int index = 0; index < dogRegister.size(); index++) {
                        if (taillength <= (dogRegister.get(index).gettaillength())) {
                            System.out.println(dogRegister.get(index));
                        }
                    }
                    break;

                case 3: //User deletes a dog from the register
                    System.out.println("State the name of the dog you wish to delete from the register: ");
                    String delete = keyboard.nextLine();
                    for (int del = 0; del < dogRegister.size(); del++) {
                        if (delete.equalsIgnoreCase(dogRegister.get(del).getName())) {
                            System.out.println("\nThe dog with the given name has been deleted from the register.");
                            dogFound = true;
                            dogRegister.remove(del);
                            System.out.print(dogRegister + "\n");
                        }
                    }
                    {
                        if (!dogFound)
                            ;
                        System.out.println("A dog by that name is not registered in our system.");
                    }
                    break;

                case 4:
                    System.out.println("\nThe program has now ended.");
                    toEnd = true;
            }
        }
    }
}

您需要将else{}块移到循环之外，并使用第二个变量确定是否找到了现有的dog，然后将其设置为true。然后您的else{}块改为读取，if！狗发现{}

否则，您的代码将打印未找到的行，每当它遇到每一只不是被寻找的狗时，我相信您会看到。e、 g

dogs = ["Jack","Pooch","Fido","Fluffy"]

如果您尝试删除Fluffy，则执行过程如下所示：

"Jack"  isn't "Fluffy", print "not found."
"Pooch" isn't "Fluffy", print "not found."
"Fido"  isn't "Fluffy", print "not found."
"Fluffy"  is  "Fluffy", remove and print "removed."

---

您应该重新考虑您的算法，特别是检查用于dogRegister的类的javadoc——我想它是从java.util.Collection继承的。你需要的东西已经有了。您还应该提供所有相关信息、必要的类型定义和示例数据，以重现您的问题。也许有人会调查它。dogFound=false的计算结果为false，因此println不会打印。相反，你想要！dogfund或dogfund==false。啊，现在你只是有一个语法问题。你有一个else{}不应该存在。没有匹配的if，空块，你有一个围绕赋值的if检查。不要这样做，你的空白使代码易于阅读。谢谢你的帮助，我的输出越来越好。当我写下一只狗的名字时，它会删除它，但现在当我写下一只不存在的狗的名字时，它不会打印任何东西。我再次编辑了我的第一篇文章。我已经修复了你代码的格式问题。这将帮助您找出哪里出了问题，因为for循环中仍然有一些不应该出现的问题，我说您必须移动。如果dogFound=false仍然在循环中，并且还在使用赋值而不是比较。@Caggen为什么要添加；你认为他的影响是什么？