定义一个圆类（Circle），私有数据成员为半径（radius）、圆周长和面积

class Circle
{
private int r;//半径

public int R()
{
return r;
}
private double perimeter;//周长

public double Perimeter()
{
return 3.14*r;
}
private double area;//面积

public double Area()
{
return 3.14 * r * r;

}

public Circle(int r)
{
this.r = r;

}
public Circle()
{
this.r = 0;
}
}
主程序： Circle c = new Circle();
Console.WriteLine(c.Area());
Console.WriteLine(c.R());
Console.WriteLine(c.Perimeter());
Circle c = new Circle(5);
Console.WriteLine(c.Area());
Console.WriteLine(c.R());
Console.WriteLine(c.Perimeter());

import java.util.*;
public class Circle{
pravite static int radius=0;
pravite float zouchang,mianji;
Circle(){
zouchang=2*3.1415926*radius;
mianji=3.1415926*radius*radius;
System.out.println(zoushang\nmianji\nradius);
}
public Circle(int r)
{
radius=r;
zouchang=2*3.1415926*r;
mianji=3.1415926*r*r;

}
public static getr(){
int p;
Scanner inputr=new Scanner(System.in);
p=inputr.nextInt();
radius=p;
return p;
}
public static void main(String args[]){

Circle circle0=new Circle(getr());
Circle circle1=new Circle(8);
System.out.println(circle0.zoushang\ncircle0.mianji\ncircle0.radius);
System.out.println(circle1.zoushang\ncircle0.mianji\ncircle.radius);
new Circle();
}

}

你去问老师