Polygon从顶点制作一个，然后填充它，方法是
fillPolygon(...)：
// A simple triangle.x[0]=100; x[1]=150; x[2]=50;y[0]=100; y[1]=150; y[2]=150;n = 3;Polygon p = new Polygon(x, y, n); // This polygon represents a triangle with the above // vertices.g.fillPolygon(p); // Fills the triangle above.
