public CCircle(double r) //建構元
System.out.println("area="+pi*radius*radius);
public class instance_vs_class_01
public static void main(String args[])
CCircle cir1=new CCircle(1.0);
cir1.show(); //透過物件來呼叫show
CCircle cir2=new CCircle(2.0);
cir2.show(); //透過物件來呼叫show