java - 为什么我的 Java 程序中会出现 InputMismatchException？

Question

我用Java制作了一个狗kennel/pound，它正在工作(在eclipse中)。但是当我测试它时，我得到了这个InputMismatchException。 我执行 switch-statement 和案例的方式有问题吗？或者我的扫描仪有什么用？该程序正在编译，所以我不明白。 作业中的要求之一是程序接受以下命令:

• 注册新狗
• 增加年龄
• 列出狗
• 移除狗
• 退出

另一个要求是测试程序必须识别单词“Error”。 请帮助我!!!

这是 Dog 类:

import java.util.*;

public class Dog {

    private String dogName;
    private String dogRace;
    private int dogAge;
    private double dogWeight;

    public Dog(String name, String race, int age, double weight){
    this.dogName = name;
    this.dogRace = race;
    this.dogAge = age;
    this.dogWeight = weight;
    }

    public String getDogName (){ 
        return this.dogName;
    }
    public String getDogRace (){
        return this.dogRace;
    }
    public void birthday(){
        dogAge = dogAge+1;
    }
    public int getDogAge(){
        return this.dogAge;
    }
    public double getDogWeight(){
        return this.dogWeight;
    }
    public double getDogTailLength(){
        if (!getDogRace().equalsIgnoreCase("Tax"))
        if(!getDogRace().equalsIgnoreCase("Dachshund")){
            return ((dogAge * dogWeight)/ 10);

        }
        return 3.7;
    }

    public String toString(){
        return "Name: " + getDogName() + ", Race: " + getDogRace() + ", Age: " + getDogAge() + ", Weight: " + 
                getDogWeight() + ", Tail: " + getDogTailLength();

    }
}

这是主类:

import java.util.*;

public class Main {

    public static Scanner scan = new Scanner(System.in);

    private ArrayList <Dog> dogList = new ArrayList<Dog>();

    public ArrayList<Dog> getDogList(){
        return this.dogList;
    }

    public String dogMenu(){
        return "Choose a commande below: \n1) Register new dog \n2) Increase age \n3) List dogs \n4)"
                    + " Remove dog \n5) Exit ";
    }
    public String error(){
        return "ERROR: please choose a number between 1-5";
    }
    public void addDog(){
        System.out.println("1- Enter the dogs name: ");
        String name = scan.next();
        System.out.println("2- Enter the dogs race: ");
        String race = scan.next();
        System.out.println("3- Enter the dogs age: ");
        int age = scan.nextInt();
        System.out.println("4- Enter the dogs weight: ");
        double weight = scan.nextDouble();
        Dog newDog = new Dog(name, race, age, weight);
        getDogList().add(newDog);
        System.out.println(newDog);

    }

    public void ageDog(){
        System.out.println("Which dog would you like to age? (State the name): ");
        String write = scan.next();
        for(Dog d: getDogList()){
            if(d.getDogName().equalsIgnoreCase(write)){
                d.birthday();
            }else{
                System.out.println("ERROR: The dog doesn't exist in the kennel");

            }
        }
    }

    public void dogTail(){
        System.out.println("State the tail length: ");
        double dogTailLengthIn = scan.nextDouble();
        for(Dog d1: getDogList()){ 
            if(d1.getDogTailLength()>= dogTailLengthIn){
                System.out.println(d1);
            }
        }
        if(getDogList().isEmpty()){
            System.out.println("ERROR: There are no dogs!!!");

    }   

    }
    public void deleteDog(){
        System.out.println("Which dog do you want to delete? (State the name): ");
        String nameIn = scan.next();
        boolean delete = false; 
        for(int a = 0; a <getDogList().size();a++){
            if(getDogList().get(a).getDogName().equalsIgnoreCase(nameIn)){
                getDogList().remove(a);
                delete = true;
            }
        }
        if(delete){
            System.out.println("The dog " + nameIn + " is deleted from the register.");
        }else{
            System.out.println("The dog " + nameIn + " doesn't exist in the register.");
        }
    }
    public void exit(){
        System.out.println("Thank you. Hope to see you soon!");
        scan.close();
        System.exit(0);
    }
    public static void main(String[] args){

        /*      Dog betty = new Dog("pudel", "Betty", 4, 22, 1.5); 

        Dog jonte = new Dog("rotweiler", "Jontis", 8, 60, 2);

        Dog jonas = new Dog("chihuahua", "Jonis", 2, 5, 0.3);*/

        Main kennel = new Main();

        while (true){ 
            System.out.print(kennel.dogMenu());
            int write = scan.nextInt();

            switch(write){

            case 1: 
                kennel.addDog();
                break; 

            case 2:
                kennel.ageDog();
                break;

            case 3:
                kennel.dogTail();
                break;

            case 4:
                kennel.deleteDog();
                break;

            case 5:
                kennel.exit();
            default: 
                System.out.println(kennel.error());
            }
        }
    }
}

问题是这样的:

Choose a commande below:
1) Register new dog
2) Increase age
3) List dogs
4) Remove dog
5) Exit

[IN:wrong command]
    java.util.concurrent.TimeoutException [LOOKING FOR: Any of [[fel case insensitive], [error case insensitive]]]
    [ERR: Exception in thread "main" java.util.InputMismatchException
      at java.util.Scanner.throwFor(Scanner.java:864)
      at java.util.Scanner.next(Scanner.java:1485)
      at java.util.Scanner.nextInt(Scanner.java:2117)
      at java.util.Scanner.nextInt(Scanner.java:2076)
      at Main.main(Main.java:96)]

在每种情况下我都明白这一点!!

Answer 1

您收到 InputMismatchException 是因为您正在输入 String 作为输入，但 int write = scan.nextInt(); 需要来自 user 的 int 值，因此存在 datatype 的 mismatch。如果您输入选项的编号而不是字符串，您的代码将正常工作，但您仍然需要更改输入Error