public class PaintRound{
    /**
     * @author Dream_e.
     * @version  v1.0
     */
    private int r;//圓的半徑
    PaintRound(int r){
        this.r = r;
    }
    public void paint(){
        int y = 2*r;//y的最大值為半徑的2倍
        int x = 0;
        int c = 0;
        int z = 2;//座標軸遞減量.
        for(int j = y; j >= 0; j-=z){
            x = getX(r,y);
            System.out.print(getSpace(x)+"*");
            c = (r-x)*2;
            System.out.println(getSpace(c)+"*");
            y-=z;
        }
    }
    //計算X座標.
    private int getX(int r, int y){
        double temp = Math.sqrt(r*r-(r-y)*(r-y));//根據圓內的正角三角形計算出圓上某點到圓心的X軸距離
        int x = (int)Math.round(r-temp);
        return x;
    }
    //計算要列印的空格數量.
    private String getSpace(int c){
        String space = " ";
        for(int i = 0; i < c; i++){
            space += " ";
        }
        return space;
    }
    public static void main(String[] args){
        new PaintRound(10).paint();
    }
}