新手JAVA-接口练习2

//fimename MyInterface.java
import java.text.DecimalFormat;
interface Shape//接口
{
public static final float PI = 3.14F;//接口常量声明
abstract double area();//抽象方法
abstract double volume();
}
class Cylinder implements Shape
{
private double radius;
private int height;
public Cylinder(double r, int h)
{
radius = r;
height = h;
}
public double area(){
return PI * radius *radius;
}
public double volume(){
return area() * height;
}
}
class MyInterface
{
public static void main(String[] args)
{
Cylinder a = new Cylinder(2,3);
DecimalFormat myFormat = new DecimalFormat("0.00");//格式,保留2位小数点
System.out.println("圆柱体底面积是" + myFormat.format(a.area()));
System.out.println("圆柱体底体积是" + myFormat.format(a.volume()));
}
}