public interface Shape{
public double area();
}
// 圆
public class Circle implements Shape{
public double area(){
return 3.14*r*r;
}
private double r;
public double getR(){ return r;}
public void setR(double r){ this.r = r;}
}
// 正方形
public class Square implements Shape{
public double area(){
return r*r;
}
private double r;
public double getR(){ return r;}
public void setR(double r){ this.r = r;}
}