Java-006 对象的组合与复用实例

如果一个对象a组合了另一个对象b，那么对象a就可以委托对象b调用其方法：

class Circle {
	double r;		//定义圆的半径
	double area;	//定义圆的面积
	Circle(double R) {
		r = R;
	}
	void setR(double R) {
		r = R;
	}
	double getR() {
		return r;
	}
	double getArea() {
		area = 3.14*r*r;
		return area;
	}
}

class Circular {
	Circle bottom;	//定义圆锥的底
	double height;	//定义高
	Circular (Circle c,double h){
		bottom = c;
		height = h;
	}
	double getVolme() {
		return bottom.getArea() * height/3;
	}
}
public class Example3 {
	public static void main(String[] args) {
		Circle c = new Circle(6);
		System.out.println("半径是："+c.getR());
		Circular circular = new Circular(c, 20);
		System.out.println("圆锥体积是："+circular.getVolme());
	}
}