interface A{
public abstract void Circumference();
public abstract void Area();
}
class Rectangular implements A{
double circumference=0;
double area=0 ;
public void Circumference(double a,double b){
circumference=2*(a+b);
}
public void Area(double a,double b){
area=a*b ;
}
}
说无法实现第二个方法Area