JavaFX - Drawing a Polygon

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Polygon is geometrically defined as a closed shape formed by a number of coplanar line segments connected from end to end. The name "polygon" is derived from the Greek words, "poly" meaning "many" and "gonia" meaning "angles".

A polygon is described by two parameters, namely, the length of its sides and the measures of its interior angles.

There are various types of Polygons based on the numbers of sides and angles. They are listed below −

• If a polygon has three sides, then it is referred to as a triangle.

• If a polygon has four sides, then it is known as quadrilateral. Shapes like rectangles, squares, parallelogram etc., are all types of quadrilaterals.

• If a polygon has five sides, then it is known as a pentagon. Similarly, the polygon with six sides is called hexagon, seven sides is heptagon, eight sides is octagon etc.

Polygon in JavaFX

In JavaFX, a polygon is represented by a class named Polygon. This class belongs to the package javafx.scene.shape.

By instantiating this class, you can create a polygon node in JavaFX. You need to pass the x, y coordinates of the points by which the polygon should be defined in the form of a double array.

You can pass the double array as a parameter of the constructor of this class as shown below −

Polygon polygon = new Polygon(doubleArray);

Or, by using the getPoints() method as follows −

polygon.getPoints().addAll(new Double[]{ List of XY coordinates separated by commas });

Steps to Draw Polygon

To draw a polygon in JavaFX, follow the steps given below.

Step 1: Creating a Polygon

Create a polygon in JavaFX by instantiating the class named Polygon which belongs to a package javafx.scene.shape within the start() method. You can instantiate this class as follows.

public class ClassName extends Application {     
   public void start(Stage primaryStage) throws Exception {
      //Creating an object of the class Polygon 
      Polygon hexagon = new Polygon();   
   }    
}

Step 2: Setting Properties to the Polygon

Specify a double array holding the XY coordinates of the points of the required polygon (hexagon in this example) separated by commas, using the getPoints() method of the Polygon class, as follows.

//Adding coordinates to the hexagon 
hexagon.getPoints().addAll(new Double[]{        
   200.0, 50.0, 
   400.0, 50.0, 
   450.0, 150.0,          
   400.0, 250.0, 
   200.0, 250.0,                   
   150.0, 150.0, 
})

Step 3: Adding Polygon Object to Group

In the start() method, instantiate the class named Group, which belongs to the package javafx.scene, by passing the Polygon object, created in the previous step, as a parameter value to its constructor.

Group root = new Group(hexagon);

Step 4: Launching Application

Once the 2D object is created, follow the given steps below to launch the application properly −

• Firstly, instantiate the class named Scene by passing the Group object as a parameter value to its constructor. To this constructor, you can also pass dimensions of the application screen as optional parameters.

• Then, set the title to the stage using the setTitle() method of the Stage class.

• Now, a Scene object is added to the stage using the setScene() method of the class named Stage.

• Display the contents of the scene using the method named show().

• Lastly, the application is launched with the help of the launch() method.

Example

Following is a program which generates a Polygon (hexagon) using JavaFX. Save this code in a file with the name PolygonExample.java.

import javafx.application.Application; 
import javafx.scene.Group; 
import javafx.scene.Scene; 
import javafx.scene.shape.Polygon; 
import javafx.stage.Stage;  

public class PolygonExample extends Application { 
   @Override 
   public void start(Stage stage) {        
      //Creating a Polygon 
      Polygon polygon = new Polygon();  
       
      //Adding coordinates to the polygon 
      polygon.getPoints().addAll(new Double[]{ 
         200.0, 50.0, 
         400.0, 50.0, 
         450.0, 150.0,          
         400.0, 250.0, 
         200.0, 250.0,                   
         150.0, 150.0, 
      }); 
          
      //Creating a Group object  
      Group root = new Group(polygon); 
         
      //Creating a scene object 
      Scene scene = new Scene(root, 600, 300);  
      
      //Setting title to the Stage 
      stage.setTitle("Drawing a Polygon"); 
         
      //Adding scene to the stage 
      stage.setScene(scene); 
      
      //Displaying the contents of the stage 
      stage.show(); 
   } 
   public static void main(String args[]){ 
      launch(args); 
   } 
}

Compile and execute the saved java file from the command prompt using the following commands.

javac --module-path %PATH_TO_FX% --add-modules javafx.controls PolygonExample.java 
java --module-path %PATH_TO_FX% --add-modules javafx.controls PolygonExample

Output

On executing, the above program generates a JavaFX window displaying a polygon as shown below.

Example

Now, let us try to draw polygons other than a hexagon, say a rhombus. Save this code in a file with the name RhombusExample.java.

import javafx.application.Application; 
import javafx.scene.Group; 
import javafx.scene.Scene; 
import javafx.scene.shape.Polygon; 
import javafx.stage.Stage;  

public class RhombusExample extends Application { 
   @Override 
   public void start(Stage stage) {        
      //Creating a Polygon 
      Polygon polygon = new Polygon();  
       
      //Adding coordinates to the polygon 
      polygon.getPoints().addAll(new Double[]{ 
         300.0, 50.0, 
         450.0, 150.0, 
         300.0, 250.0, 
         150.0, 150.0, 
      }); 
          
      //Creating a Group object  
      Group root = new Group(polygon); 
         
      //Creating a scene object 
      Scene scene = new Scene(root, 600, 300);  
      
      //Setting title to the Stage 
      stage.setTitle("Drawing a Polygon"); 
         
      //Adding scene to the stage 
      stage.setScene(scene); 
      
      //Displaying the contents of the stage 
      stage.show(); 
   } 
   public static void main(String args[]){ 
      launch(args); 
   } 
}

Compile and execute the saved java file from the command prompt using the following commands.

javac --module-path %PATH_TO_FX% --add-modules javafx.controls RhombusExample.java 
java --module-path %PATH_TO_FX% --add-modules javafx.controls RhombusExample

Output

On executing, the above program generates a JavaFX window displaying a rhombus as shown below.