用方法的重载，实现圆，矩形，三角形的面积

在面向对象编程中，你可以通过方法的重载（Overloading）来实现计算圆、矩形和三角形面积的功能。这里是一个简单的例子，假设我们有一个Shape接口，然后有Circle、Rectangle和Triangle这三个类分别继承自Shape并提供各自的面积计算方法：

// Shape接口
public interface Shape {
    double getArea();
}

// Circle类实现了Shape接口
public class Circle implements Shape {
    private double radius;

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

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

// Rectangle类也实现Shape接口
public class Rectangle implements 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;
    }
}

// Triangle类同样实现Shape接口
public class Triangle implements 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; // 使用海伦公式或其他适合三角形的方式
    }
}

// 在主函数中，你可以创建任意形状的对象并调用getArea方法来获取面积
public static void main(String[] args) {
    Shape circle = new Circle(5);
    Shape rectangle = new Rectangle(4, 6);
    Shape triangle = new Triangle(3, 7);

    System.out.println("Circle area: " + circle.getArea());
    System.out.println("Rectangle area: " + rectangle.getArea());
    System.out.println("Triangle area: " + triangle.getArea());
}