015 ポリモーフィズム（インスタンス型の確認） 017 解答例

class Shape {
    public void draw() {
        System.out.println("Drawing a shape");
    }
}

class Circle extends Shape {
    @Override
    public void draw() {
        System.out.println("Drawing a circle");
    }
}

class Rectangle extends Shape {
    @Override
    public void draw() {
        System.out.println("Drawing a rectangle");
    }
}

public class Main {
    public static void main(String[] args) {
        // 動的な配列を作成し、異なる形状のオブジェクトを格納
        Shape[] shapes = new Shape[3];
        shapes[0] = new Circle();
        shapes[1] = new Rectangle();
        shapes[2] = new Shape(); // Shapeも格納可能

        // 各オブジェクトがどのクラスのインスタンスかを確認
        for (Shape shape : shapes) {
            if (shape instanceof Circle) {
                System.out.println("This is an instance of Circle");
            } else if (shape instanceof Rectangle) {
                System.out.println("This is an instance of Rectangle");
            } else if (shape instanceof Shape) {
                System.out.println("This is an instance of Shape");
            }
        }
    }
}

This is an instance of Circle
This is an instance of Rectangle
This is an instance of Shape