程序5-13
interface Shape2D{ //定义Shape2D接口
final double pi=3.14; //数据成员一定要初始化
public abstract double area(); //抽象方法，不需要定义处理方式
}
class Circle implements Shape2D{
double radius;
public Circle(double r){ //构造方法
radius=r;
}
public double area(){
return (pi * radius * radius);
}
}
class Rectangle implements Shape2D{
int width,height;
public Rectangle(int w,int h){ //构造方法
width=w;
height=h;
}
public double area(){
return (width * height);
}
}
public class InterfaceTester {
public static void main(String args[]){
Rectangle rect=new Rectangle(5,6);
System.out.println("Area of rect = " + rect.area());
Circle cir=new Circle(2.0);
System.out.println("Area of cir = " + cir.area());
}
}