急求Java代码,定义一个Circle(圆类型)答:public class Exam { public static void main(String[] args){ Circle c=new Circle(3,4,5);System.out.printf("圆心:(%f,%f),半径:%f,面积:%f",c.x,c.y,c.r,c.countArea());} } class Circle { public Circle(){ this(0,0,0);} public Circle(double x,double y,double...