java用“*”在控制台打印出一个圆

import java.util.Scanner;

public class Circle {
public static void main(String[] args) {
System.out.println("请输入圆的半径:");
Scanner sc = new Scanner(System.in);
int r = sc.nextInt();
for (int y = 0; y <= 2 * r; y += 2) {//y的步长为2,改变y的步长可以将圆形变成椭圆
int x = (int)Math.round(r - Math.sqrt(2 * r * y - y * y));
int len = 2 * (r - x);

for (int i = 0; i <= x; i++) {
System.out.print(' ');
}
System.out.print('*');

for (int j = 0; j <= len; j++) {
System.out.print(' ');
}

System.out.println('*');

}
}
}