java - 在 ArrayList 中存储不同类的对象

Question

我有一个抽象的动物类和其他子类，如爬行动物，它们被进一步继承。
我创建了数组来初始化动物，如下所示:

public void initializeArray()
{
    zooAnimal = new Animal[10];         // We will make 10 animals:

    // Polymorphism allows us to assign an object of a subclass to an 
    // object reference to a superclass/ancestor.
    zooAnimal[0] = new Kookaburra("Kelly",5);       // A 5kg kookaburra
    zooAnimal[1] = new Lizard("Lizzy",2,3);         // A 2kg, 3-year-old lizard
    zooAnimal[2] = new Crocodile("Colin", 200, 7);      // a 7-yo 200kg croc.
    zooAnimal[3] = new Rosella("Katie", 2, "Crimson");      // a 2-yo    Crimson Rosella
    zooAnimal[4] = new Rosella("Rosie", 4, "Green");        // a 4-yo Green Rosella
    zooAnimal[5] = new Snake("Boris","Brown",15,3); // A Brown Snake, 15kg, 3 years
    zooAnimal[7] = new Snake("Rita","Rattle",22,1); // A Rattle Snake, 22kg, 1 years
    zooAnimal[6] = new Dolphin("Dolly", 142, 6);    // A heavy, 6-yo dolphin.
    zooAnimal[8] = new Kookaburra("Kenneth",4);     // A 4kg kookaburra
    zooAnimal[9] = new Rosella("Yippy", 1, "Yellow");       // a 1-yo Yellow Rosella
}

但我想使用 ArrayList 而不是数组来实现相同的效果。
如何做到这一点？

我的 Animal 类和子类如下所示:

动物类

public abstract class Animal
{
    private int weight;
    private int age;
    private String name;

    protected Animal(String name, int weight, int age)
    {
        this.name = name;
        this.weight = weight;
        this.age = age;
    }

    public final int getWeight() { return weight; }

    public final int getAge() { return age; }

    public final String getName() { return name; }

    public abstract void makeNoise();       // Must be implemented by a subclass

    /** Provides a default description of the animal.
    * Sub-classes should override. */
    public String toString()
    {
        return "Animal Object: [name=" + name + ", age=" + age + ", weight=" + weight + "]";
    }
}

我有一个 Bird 类(Animal 类的子类)，一个 Kookabura 类( 的子类) Animal)、Reptile 类(Animal 类的子类)和一个Lizard 子类( 的子类)爬虫类)等等!!

Answer 1

您只需要声明一个 ArrayList<Animal> , 并使用 add(Animal)方法而不是赋值(多态允许你这样做):

private ArrayList<Animal> zooAnimals;

public void initializeArray() {
    // this 10 is optional, but it's good to specify it 
    // when you know the final length of your list in advance
    zooAnimals = new ArrayList<>(10);

    zooAnimals.add(new Kookaburra("Kelly", 5)); // A 5kg kookaburra
    zooAnimals.add(new Lizard("Lizzy", 2, 3)); // A 2kg, 3-year-old lizard
    zooAnimals.add(new Crocodile("Colin", 200, 7)); // a 7-yo 200kg croc.
    zooAnimals.add(new Rosella("Katie", 2, "Crimson")); // a 2-yo    Crimson Rosella
    zooAnimals.add(new Rosella("Rosie", 4, "Green")); // a 4-yo Green Rosella
    zooAnimals.add(new Snake("Boris", "Brown", 15, 3)); // A Brown Snake, 15kg, 3 years
    zooAnimals.add(new Snake("Rita", "Rattle", 22, 1)); // A Rattle Snake, 22kg, 1 years
    zooAnimals.add(new Dolphin("Dolly", 142, 6)); // A heavy, 6-yo dolphin.
    zooAnimals.add(new Kookaburra("Kenneth", 4)); // A 4kg kookaburra
    zooAnimals.add(new Rosella("Yippy", 1, "Yellow")); // a 1-yo Yellow Rosella
}