Complete Gasket

Here is the complete program. Notice how the parameters in the recursive calls (that draw hollow triangles) are the same as in the base cases (that draw solid triangles.)

import javafx.application.*;  
import javafx.stage.*;        
import javafx.scene.*;  
import javafx.scene.shape.*; 
import javafx.scene.paint.*;  

class STriangle extends Group
{
  STriangle( Color color, int order, int limit, double x0, double y0, double x1, double y1, double x2, double y2 )
  {    
    // Calculate midpoints of the three sides
    double xL = (x0+x1)/2.0; double yL = (y0+y1)/2.0;
    double xR = (x1+x2)/2.0; double yR = (y1+y2)/2.0;
    double xB = (x0+x2)/2.0; double yB = (y0+y2)/2.0;
    
    // If the depth limit has not been reached,
    // construct the current triangle as three hollow little triangles
    // recursively using this very method.
    if ( order < limit )
    {
      order++ ;
      STriangle triL = new STriangle( color, order, limit, x0, y0, xL, yL, xB, yB ); // lower left
      STriangle triR = new STriangle( color, order, limit, xB, yB, xR, yR, x2, y2 ); // lower right
      STriangle triT = new STriangle( color, order, limit, xL, yL, x1, y1, xR, yR ); // top
      getChildren().addAll( triL, triR, triT );  
    }
    
    // If the depth limit has been reached,
    // construct the current triangle as three solid little triangles
    else
    {
      Polygon triL = new Polygon( x0, y0, xL, yL, xB, yB ); // lower left
      triL.setFill( color );
      Polygon triR = new Polygon( xB, yB, xR, yR, x2, y2 ); // lower right
      triR.setFill( color );
      Polygon triT = new Polygon( xL, yL, x1, y1, xR, yR ); // top
      triT.setFill( color );
      getChildren().addAll( triL, triR, triT );  
    }
  
  }
}
  
public class Sierpinski extends Application
{ 
  
  public void start(Stage stage) 
  { 
    double sceneWidth=400, sceneHeight=400 ;  
  
    double x0 = 0, y0 = sceneHeight, x1= sceneWidth/2, y1=0, x2= sceneWidth, y2= sceneHeight;
    STriangle tri = new STriangle(  Color.BLUE, 1, 6, x0, y0, x1, y1, x2, y2 );
    
    Scene scene = new Scene( tri, sceneWidth, sceneHeight, Color.SNOW ); 
    stage.setTitle("Sierpinski Gasket"); 
    stage.setScene(scene); 
    stage.show(); 
  }      

}

Line line = new Line(  ,  , ,  );