public class Cone<E> {
	    double height;
	    E bottom;           //用泛型类E声明对象bottom
	    public Cone(E b) {
		    bottom = b;
	    }
	    public void setHeight(double h) {
		    height = h;
	    }
	    public double computerVolume() {
		    String s = bottom.toString();//泛型变量只能调用从Object类继承的或重写的方法
		    double area = Double.parseDouble(s);
		    return 1.0 / 3.0 * area * height;
	    }
}