If you look at it mathematically, the Union operation was fundamentally used in the concept of set theory. This operation is defined as the combination of two different sets into one. In here, all the elements of one set and merged within another set, regardless of any duplicities. This concept is then adopted by various techniques in computer programming.

For instance, union operation when performed in SQL combines two or more result-sets into one common result set. It is also used in programming languages like C, C++, Java, Python etc. as an operator or a method.

Similarly, JavaFX also provides union operation on 2D shapes.

Union Operation in JavaFX

JavaFX provides union operation which can be performed on 2D shapes. In here, the areas of two or more shapes are combined together to form a bigger and a more complex shape. Thus, the union operation takes two or more shapes as inputs and returns the combined area occupied by them as shown below.

You can perform union operation on the shapes using the method called union(). Since this is a static method, you should call it using the class name (Shape or its subclasses) as shown below.

Shape shape = Shape.subtract(circle1, circle2); 

Example

Following is an example of the union operation. In here, we are drawing two circles and performing a union operation on them. Save this code in a file with the name unionExample.java.

import javafx.application.Application; 
import javafx.scene.Group; 
import javafx.scene.Scene; 
import javafx.scene.paint.Color; 
import javafx.stage.Stage; 
import javafx.scene.shape.Circle; 
import javafx.scene.shape.Shape; 
         
public class UnionExample extends Application {  
   @Override 
   public void start(Stage stage) { 
      //Drawing Circle1 
      Circle circle1 = new Circle();         
      
      //Setting the position of the circle 
      circle1.setCenterX(250.0f); 
      circle1.setCenterY(135.0f); 
      
      //Setting the radius of the circle 
      circle1.setRadius(100.0f); 
      
      //Setting the color of the circle 
      circle1.setFill(Color.DARKSLATEBLUE);     
       
      //Drawing Circle2 
      Circle circle2 = new Circle();         
      
      //Setting the position of the circle 
      circle2.setCenterX(350.0f);
      circle2.setCenterY(135.0f); 
      
      //Setting the radius of the circle 
      circle2.setRadius(100.0f); 
      
      //Setting the color of the circle  
      circle2.setFill(Color.BLUE);  
       
      //Performing union operation on the circle 
      Shape shape = Shape.union(circle1, circle2); 
      
      //Setting the fill color to the result 
      shape.setFill(Color.DARKSLATEBLUE); 
       
      //Creating a Group object  
      Group root = new Group(shape); 
         
      //Creating a scene object 
      Scene scene = new Scene(root, 600, 300);  
      
      //Setting title to the Stage 
      stage.setTitle("Union Example"); 
         
      //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 UnionExample.java 
java --module-path %PATH_TO_FX% --add-modules javafx.controls UnionExample

Output

On executing, the above program generates a JavaFX window displaying the following output −

Example

Let us try to perform union operation on shapes other than a circle, like an ellipse. Save this file under the name EllipseUnionOperation.java.

import javafx.application.Application; 
import javafx.scene.Group; 
import javafx.scene.Scene; 
import javafx.scene.paint.Color; 
import javafx.stage.Stage; 
import javafx.scene.shape.Ellipse; 
import javafx.scene.shape.Shape; 
         
public class EllipseUnionOperation extends Application {  
   @Override 
   public void start(Stage stage) { 
      Ellipse ellipse1 = new Ellipse();               
      ellipse1.setCenterX(250.0f); 
      ellipse1.setCenterY(100.0f); 
      ellipse1.setRadiusX(150.0f); 
      ellipse1.setRadiusY(75.0f); 
      ellipse1.setFill(Color.BLUE);     

      Ellipse ellipse2 = new Ellipse();      
      ellipse2.setCenterX(350.0f); 
      ellipse2.setCenterY(100.0f); 
      ellipse2.setRadiusX(150.0f); 
      ellipse2.setRadiusY(75.0f);     
      ellipse2.setFill(Color.RED);  
 
      Shape shape = Shape.union(ellipse1, ellipse2); 
      
      //Setting the fill color to the result 
      shape.setFill(Color.DARKSLATEBLUE); 
       
      //Creating a Group object  
      Group root = new Group(shape); 
         
      //Creating a scene object 
      Scene scene = new Scene(root, 600, 300);  
      
      //Setting title to the Stage 
      stage.setTitle("Union Example"); 
         
      //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 EllipseUnionOperation.java 
java --module-path %PATH_TO_FX% --add-modules javafx.controls EllipseUnionOperation

Output

On executing, the above program generates a JavaFX window displaying the following output −