Java参数应用&for循环作图“以漩涡图形实验为例”

Q21. 写一条利用for循环程序画出下面的图形。窗口大小为：170 x 170 px
“spiral” 从 (0,10),向右 160,向下 150,向左 150, 向上140…

import java.awt.*;
//调取图形包
public class Q28 {
//这个实验看上去很复杂，其实是很入门的算法
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		
		spiral(32);
		//旋转32次
	}
	public static void spiral(int num) {
		int x1 = 0;
		int y1 = 10;
		int x2 = 0;
		int y2 = 10;
		//初始坐标
		DrawingPanel panel = new DrawingPanel(170, 170);
		for (int i=1;i<=num;i++) {
		Graphics g = panel.getgraphics();
		//获得图形
		g.setColor(Color.BLACK);
		
		//每一次的旋转以四次为周期，没旋转一次减少/增加20 px
		if (i%4 ==0) {
			y2 = y1 -160 + (i/4)*20;
		}else if (i%4==1 ) {
			x2 = x1 + 160 -(i/4)*20;
		}else if (i%4==2) {
			y2 = y1 + 150 - (i/4)*20;
		}else if (i%4 ==3) {
			x2 = x1 - 150 +(i/4)*20;
		}
		g.drawLine(x1, y1, x2, y2);
		x1 = x2;
		y1 = y2;
		
		}
	}
}