package w5;

public class ShapeCalculator {
    abstract class Shape {
        public abstract double getArea();
    }
    class Circle extends Shape {
        private double radius;
        public Circle(double radius) {
            this.radius = radius;
        }
        @Override
        public double getArea() {
            return Math.PI * radius * radius;
        }
    }
    class Rectangle extends Shape {
        private double width;
        private double height;
        public Rectangle(double width, double height) {
            this.width = width;
            this.height = height;
        }
        @Override
        public double getArea() {
            return width * height;
        }
    }
    class Triangle extends Shape {
        private double base;
        private double height;
        public Triangle(double base, double height) {
            this.base = base;
            this.height = height;
        }
        @Override
        public double getArea() {
            return 0.5 * base * height;
        }
    }
    class ShapeUtil {
        public static void printArea(Shape shape) {
            System.out.println("图形面积为：" + shape.getArea());
        }
    }
    public static void main(String[] args) {
        ShapeCalculator calculator = new ShapeCalculator();
        Shape circle = calculator.new Circle(5);
        Shape rectangle = calculator.new Rectangle(4,6);
        Shape triangle = calculator.new Triangle(3,8);
        System.out.println("====== 图形面积计算器 ======");
        ShapeUtil.printArea(circle);
        ShapeUtil.printArea(rectangle);
        ShapeUtil.printArea(triangle);
    }
}