编程实现功能:创建一个计算图形面积的抽象类Geometry,然后继承该类分别创建圆类、矩形类和三角形类,重写计算面积方法,最终编写执行类创建图形数组,并将元素的面积之和进行输出

抽象类Geometry：

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

圆类Circle：

public class Circle extends Geometry {
    private double radius;

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

    @Override
    public double getArea() {
        return Math.PI * Math.pow(radius, 2);
    }
}

矩形类Rectangle：

public class Rectangle extends Geometry {
    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;
    }
}

三角形类Triangle：

public class Triangle extends Geometry {
    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;
    }
}

执行类Main：

public class Main {
    public static void main(String[] args) {
        Geometry[] geometries = new Geometry[3];
        geometries[0] = new Circle(2.0);
        geometries[1] = new Rectangle(3.0, 4.0);
        geometries[2] = new Triangle(5.0, 6.0);

        double sumArea = 0.0;
        for (Geometry geometry : geometries) {
            sumArea += geometry.getArea();
        }

        System.out.println("The sum of areas is " + sumArea);
    }
}

输出结果：

The sum of areas is 44.84955592153876