ポリモーフィズムと抽象クラス

class Animal {
    public void makeSound() {
        System.out.println("Verso...");
    }
}

class Dog extends Animal {
    public void makeSound() {
        System.out.println("Woof");
    }
}

class Cat extends Animal {
    public void makeSound() {
        System.out.println("Miao");
    }
}

Animal myAnimal1 = new Dog(); // Polymorphism
Animal myAnimal2 = new Cat(); // Polymorphism

myAnimal1.makeSound(); // Executes Dog's method (Woof)
myAnimal2.makeSound(); // Executes Cat's method (Miao)

abstract class Shape {
    String color;

    // Abstract method (no body)
    public abstract double getArea();
}

class Circle extends Shape {
    double radius;

    public Circle(double radius) {
        this.radius = radius;
    }

    // Required to implement getArea
    @Override
    public double getArea() {
        return Math.PI * radius * radius;
    }
}

abstract class Animal {
    public abstract void makeSound();
}

// This class MUST be abstract because it does not implement makeSound()
abstract class Canine extends Animal {
    // Inherits makeSound() but does not implement it
}