abstract class Shape {
    public abstract double getArea();
}

class Circle extends Shape {
    private double radius;
    public Circle(double radius) {
        this.radius = radius;
    }
    public double getArea() {
        return Math.PI * radius * radius;
    }
}

class Rectangle extends Shape {
    private double length;
    private double width;
    public Rectangle(double length, double width) {
        this.length = length;
        this.width = width;
    }
    public double getArea() {
        return length * width;
    }
}

class Triangle extends Shape {
    private double base;
    private double height;
    public Triangle(double base, double height) {
        this.base = base;
        this.height = height;
    }
    public double getArea() {
        return 0.5 * base * height;
    }
}

class ShapeUtil {
    public static void printArea(Shape shape) {
        System.out.println(shape.getArea());
    }
}

// 关键修改：类名与文件名完全一致
public class 图形面积计算器重构 {
    public static void main(String[] args) {
        Shape circle = new Circle(2);
        Shape rectangle = new Rectangle(3, 4);
        Shape triangle = new Triangle(3, 4);
        ShapeUtil.printArea(circle);
        ShapeUtil.printArea(rectangle);
        ShapeUtil.printArea(triangle);
    }
}