練習題- 第三章 畫近似圓

import java.lang.Math;public class FirstProject {    public static void main(String[] args) {        paint(40); //半徑40    }    public static void paint(int r) {     //假定圓心在座標(r,r);        int y = r * 2; //y的座標開始        int x = 0;        int c = 0; //中間空格數量        int z = 2; //每行遞減量        for (int j = r * 2; j >= 0; j=j-z) {            x = getX(r, y);            System.out.print(getSpace(x) + "*");            c = (r-x)*2;            System.out.println(getSpace(c) + "*");            y-=z;        }    }    public static int getX(int r, int y) {        //解圓標準方程的        int x = y - r;               double t = Math.sqrt((r * r) - (x * x));        return (int) Math.round(r-t);    }    public static String getSpace(int i) {        String s = "";        for (int j = 0; j < i; j++) {            s += " ";        }        return s;    }}