如果上述类不是通过继承机制，而是采用类的复用机制呢？例如，圆锥类的一个 成员变量为圆类的对象。将上述类按这种要求实现一遍。 java

以下是通过类的复用机制实现的代码：

1. 圆的类：

public class Circle {
    protected double radius;

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

    public double getPerimeter() {
        return 2 * Math.PI * radius;
    }

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

2.1 环的类：

public class Ring {
    protected Circle outerCircle;
    protected Circle innerCircle;

    public Ring(double innerRadius, double outerRadius) {
        this.outerCircle = new Circle(outerRadius);
        this.innerCircle = new Circle(innerRadius);
    }

    public double getPerimeter() {
        return outerCircle.getPerimeter() + innerCircle.getPerimeter();
    }

    public double getArea() {
        return outerCircle.getArea() - innerCircle.getArea();
    }
}

2.2 扇形的类：

public class Sector {
    protected Circle circle;
    protected double angle;

    public Sector(double radius, double angle) {
        this.circle = new Circle(radius);
        this.angle = angle;
    }

    public double getPerimeter() {
        return circle.getPerimeter() * angle / 360;
    }

    public double getArea() {
        return circle.getArea() * angle / 360;
    }
}

2.3 圆锥的类：

public class Cone {
    protected Circle base;
    protected double height;

    public Cone(Circle base, double height) {
        this.base = base;
        this.height = height;
    }

    public double getSurfaceArea() {
        double l = Math.sqrt(base.radius * base.radius + height * height);
        return Math.PI * base.radius * l + Math.PI * base.radius * base.radius;
    }

    public double getVolume() {
        return Math.PI * base.radius * base.radius * height / 3;
    }
}

2.4 圆台的类：

public class Frustum {
    protected Cone cone1;
    protected Cone cone2;

    public Frustum(double bottomRadius, double topRadius, double height) {
        Circle bottomCircle = new Circle(bottomRadius);
        Circle topCircle = new Circle(topRadius);
        this.cone1 = new Cone(bottomCircle, height);
        this.cone2 = new Cone(topCircle, height);
    }

    public double getSurfaceArea() {
        return cone1.getSurfaceArea() + cone2.getSurfaceArea() + Math.PI * (cone1.base.radius + cone2.base.radius) * Math.sqrt((cone1.base.radius - cone2.base.radius) * (cone1.base.radius - cone2.base.radius) + cone1.height * cone1.height);
    }

    public double getVolume() {
        return cone1.getVolume() - cone2.getVolume();
    }
}