Question

我试图让用户在我的virtualZoo.java文件运行时选择一种动物。它可以编译，但是一旦用户输入选择，我就会收到一条错误消息，显示“错误树类型”。下面的代码用于virtualZoo.java，animal.java和dog.java。有人指示我使用switch语句下面的对象，但不了解其实现。

virtualZoo.java

import java.util.Scanner;

public class VirtualZoo{
public static void main(String[] args) {

                    Animal cat = new Animal("Cat", "Meow");
                    Animal dog = new Animal("Dog", "Woof");
                    Animal duck = new Animal("Duck", "Quak");

    // create Scanner
    Scanner input;
    input = new Scanner(System.in);
        double userInput;
                    System.out.println("Welcome to the Zoo");
                    System.out.println("Pick select an animal to visit");
        System.out.println("=================================");
        System.out.println("===========MAIN MENU=============");
        System.out.println("=================================");
        System.out.println("==  0) Cat    ===================");
        System.out.println("==  1) Dog    ===================");
        System.out.println("==  2) Duck   ===================");
        System.out.println("== -1) EXIT   ===================");
        System.out.println("=================================");
        System.out.println();System.out.println();
        System.out.println( "Input  : ");
        Scanner sc = new Scanner(System.in);
        userInput = sc.nextInt();


    switch (sc.nextInt()) {
        case 0:
            System.out.println(cat);
            break;
        case 1:
            System.out.println(dog);
            break;
        case 2:
            System.out.println(duck);
            break;
        case -1:
            System.out.println("Your name is short length.");
            break;
        default:
            break;
    }
                    duck.speak();
                    dog.speak();
                    cat.speak();


  }

}

animal.java（virtualZoo.java中的动物类）

public class Animal {
private String animalSound;
private String animalType = "";

//set animal sound
public void setSound(String sound) { this.animalSound = sound; }

//get animal sound
public String getSound() { return animalSound; }
public void setType(String type) { this.animalType = type; }

//get animal type
public String getType() { return animalType; }


public Animal(String animalType, String animalSound)
{
    this.animalSound = "";
    this.animalType = animalType;
    this.animalSound = animalSound;
}

public void speak()
 {
    System.out.println("The " + animalType + " says " + animalSound);
 }
}

dog.java（动物类中的狗类）

public class Dog extends Animal {

public Dog(String animalType, String animalSound) {
    super(animalType, animalSound);
}

@Override
public void speak(){

    System.out.println("This dog barks");

  }
}

Answer 1

您步入正轨，但我相信您有一些错误。我假设您发布的代码与为您提供错误的代码略有不同（我已测试，但未收到错误）

在这里，您将从用户那里获得2个输入。我相信您只想得到1。

userInput = sc.nextInt(); switch (sc.nextInt())

此外，userInput 应该是int类型，而不是双精度。

您有狗班，但没有猫/鸭班

您似乎正在尝试使用工厂模式，但我不确定100％。您可以创建一个AnimalFactory类。否则，“动物”类会令人困惑。我假设您没有使用工厂模式。

您会注意到一些事情：

我从Object覆盖了toString()方法。 System.out.println将调用toString()方法。

猫，鸭和狗都从Animal延伸，因此您的Animal animalSelected可以是任何一种！

动物有2种抽象方法。这些方法必须在任何子类（猫，狗，鸭）中被覆盖。声明方法意味着我们可以在Animal类中使用这些方法。它还允许我们在任何Animals上调用方法。

例如，即使Animal没有定义该方法的主体，您也可以使用animalSelected.getAnimalSound()。

import java.util.Scanner;

public class VirtualZoo
{
    public static void main(String[] args) 
    {
    // Options
    final int catType = 0,
              dogType = 1,
              duckType = 2,
              exit = -1;

    // create Scanner
    Scanner input;
    input = new Scanner(System.in);
        int userInput;
                    System.out.println("Welcome to the Zoo");
                    System.out.println("Pick select an animal to visit");
        System.out.println("=================================");
        System.out.println("===========MAIN MENU=============");
        System.out.println("=================================");
        System.out.println("==  " + catType + ") Cat    ===================");
        System.out.println("==  " + dogType + ") Dog    ===================");
        System.out.println("==  " + duckType + ") Duck   ===================");
        System.out.println("== " + exit + ") EXIT   ===================");
        System.out.println("=================================");
        System.out.println();
        System.out.println();
        System.out.println( "Input  : ");
        Scanner sc = new Scanner(System.in);
        userInput = sc.nextInt();

    Animal animalSelected = null;

    switch (userInput) 
    {
        case catType:
            animalSelected = new Cat();
            break;
        case dogType:
            animalSelected = new Dog();
            break;
        case 2:
            animalSelected = new Duck();
            break;
        case -1:
            System.out.println("Your name is short length.");
            break;
        default:
            break;
    }

    if (animalSelected != null)
    {
        System.out.println(animalSelected);
    }
}

}

public abstract class Animal 
{
    public abstract String getAnimalSound();
    public abstract String getAnimalType();

    @Override
    public String toString()
    {
       return "The " + getAnimalType() + " says " + getAnimalSound();
    }
}

public class Duck extends Animal 
{
    @Override
    public String getAnimalSound() 
    {
        return "quacks";
    }

    @Override
    public String getAnimalType() 
    {
        return "Duck";
    }

}

public class Cat extends Animal 
{
    @Override
    public String getAnimalSound() 
    {
        return "meows";
    }

    @Override
    public String getAnimalType() 
    {
        return "Cat";
    }
}


public class Dog extends Animal 
{
    @Override
    public String getAnimalSound() 
    {
        return "barks";
    }

    @Override
    public String getAnimalType() 
    {
        return "Dog";
    }
}

从类内部进行对象选择和打印

1 个答案: