import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.geom.GeneralPath;

import javax.swing.JFrame;

public class NationalFlag extends JFrame {
   private int width=288,height=width/3*2;
   private double maxR=0.15,minR=0.05;
   private double maxX=0.50,maxY=0.50;
   private double[] minX={0.75,0.85,0.85,0.75};
   private double[] minY={0.35,0.45,0.60,0.70};
  public NationalFlag(){
  setTitle("国旗 - by yuxiaoer");
  setDefaultCloseOperation(EXIT_ON_CLOSE);//用户单击窗口的关闭按钮时程序执行的操作
  }

public void paint(java.awt.Graphics graphics){
super.paint(graphics);
java.awt.Graphics2D g=(java.awt.Graphics2D)graphics;

g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);

//棋面
g.setColor(java.awt.Color.red);
g.fillRect(50, 50, width, height);
g.setColor(java.awt.Color.yellow);
//画大星星
double ox=height*maxX,oy=height*maxY;
g.fill(createPentacle(ox,oy,height*maxR,-Math.PI/2));

//画小星星
for(int idx=0;idx<4;idx++){
double sx=minX[idx]*height,sy=minY[idx]*height;
double theta=Math.atan2(oy-sy, ox-sy);
g.fill(createPentacle(sx,sy,height*minR,theta));
}

}
/*
* 创建一个五角星形状，该五角星的中心坐标为(sx,sy),中心到顶点的距离为radius 其中某个顶点与中心连线的偏移角度
* 为theta(弧度)
*/
public static java.awt.Shape createPentacle(double sx,double sy,double radius,double theta){
final double arc=Math.PI/5;
final double rad=Math.sin(Math.PI/10)/Math.sin(3*Math.PI/10);
GeneralPath path=new GeneralPath();
path.moveTo(1, 0);
for(int idx=0;idx<5;idx++){
path.lineTo(rad*Math.cos((1+2*idx)*arc), rad*Math.sin((1+2*idx)*arc));

path.lineTo(Math.cos(2*(idx+1)*arc), Math.sin(2*(idx+1)*arc));

}
path.closePath();
AffineTransform atf=AffineTransform.getScaleInstance(radius, radius);
atf.translate(sx/radius, sy/radius);
atf.rotate(theta);
return 
atf.createTransformedShape(path);
}

public static void main(String[] args) {
// TODO Auto-generated method stub
      NationalFlag flag=new  NationalFlag();
      flag.setBounds(100,100,400,400);
      flag.setVisible(true);
}
}