One Triangle as a Group

Here is a program that draws a solid triangle. The three vertices of the triangle are

• (x0, y0) — bottom left
• (x1, y1) — top
• (x2, y2) — bottom right

Class Triangle extends Group. The class contains a single Polygon. If all you wanted was one triangle you could just add a Polygon to a Pane and put it in the scene graph in start(). But more will be done with our Triangle.

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

class Triangle extends Group
{
  Triangle( Color color, double x0, double y0, double x1, double y1, double x2, double y2 )
  {
    Polygon tri = new Polygon( x0, y0, x1, y1, x2, y2 );  
    tri.setFill( color );
    getChildren().add( tri );
  }
}
  
public class DrawTriangle extends Application
{ 
  
  public void start(Stage stage) 
  { 
    double sceneWidth=200, sceneHeight=200 ;  
  
    double x0=0, y0=sceneHeight, x1=sceneWidth/2, y1=0, x2= sceneWidth, y2=sceneHeight;
    Triangle solid = new Triangle(  Color.BLUE, x0, y0, x1, y1, x2, y2 );
    
    Scene scene = new Scene( solid, sceneWidth, sceneHeight, Color.SNOW ); 
    stage.setTitle("Solid Triangle"); 
    stage.setScene(scene); 
    stage.show(); 
  }      

}