89. 타입 검사 후 다운캐스팅과 형 변환 예외

1class Shape {
2    int size() {
3        return 1;
4    }
5}
6 
7class Circle extends Shape {
8    int r;
9 
10    Circle(int r) {
11        this.r = r;
12    }
13 
14    int size() {
15        return r * r * 3;
16    }
17}
18 
19class Rect extends Shape {
20    int w;
21    int h;
22 
23    Rect(int w, int h) {
24        this.w = w;
25        this.h = h;
26    }
27 
28    int size() {
29        return w * h;
30    }
31 
32    int round() {
33        return 2 * (w + h);
34    }
35}
36 
37public class Main {
38    public static void main(String[] args) {
39        Shape[] arr = {new Circle(2), new Rect(3, 4), new Shape()};
40        int total = 0;
41        for (Shape s : arr) {
42            if (s ( ① ) Rect) {
43                Rect r = (Rect) s;
44                total += r.round();
45            } else {
46                total += s.size();
47            }
48        }
49        System.out.println(total);
50        try {
51            Rect bad = (Rect) arr[0];
52            System.out.println(bad.w);
53        } catch (ClassCastException e) {
54            System.out.println("cast fail " + total % 10);
55        }
56    }
57}