// InterfaceDemo4.java
//接口shape
interface shape{
	double PI=3.14159;
	abstract double area();
}
//定義Rectangle類實現接口shape
class Rectangle implements shape{
	double width,height;
	public Rectangle(double w,double h){
	       width=w;
	       height=h;
	}
	public double area(){
	        return width*height;
	 }
}
      //定義Circle類實現接口shape
class Circle implements shape{
	  double radius;
	  public Circle(double r){
	          radius=r;
	  }
	  public double area(){
	          return PI*radius*radius;
	 }
}
public class InterfaceDemo4{
	   public static void main(String args[]){
	   Rectangle rect=new Rectangle(15,20);
	   System.out.println("Rectanle area="+rect.area());
	   Circle cir=new Circle(10);
	   System.out.println("Circle area="+cir.area());
}
}