Explain the Union operation on 2D shapes in JavaFX

This operation takes two or more shapes as inputs and returns the area occupied by them combined as shown below.

The union() (static) method of the javafx.scene.shape.Shape class accepts two Shape objects and returns the result of the union operation of the given objects.

Example

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 JavaFXUnionExample extends Application {
   public void start(Stage stage) {
      //Drawing circle1
      Circle circle1 = new Circle();
      circle1.setCenterX(230.0f);
      circle1.setCenterY(100.0f);
      circle1.setRadius(75.0f);
      circle1.setFill(Color.DARKRED);
      //Drawing Circle2
      Circle circle2 = new Circle();
      circle2.setCenterX(280.0f);
      circle2.setCenterY(170.0f);
      circle2.setRadius(75.0f);
      circle2.setFill(Color.DARKRED);
      //Drawing Circle3
      Circle circle3 = new Circle();
      circle3.setCenterX(330.0f);
      circle3.setCenterY(100.0f);
      circle3.setRadius(75.0f);
      circle3.setFill(Color.DARKRED);
      //Union operation
      Shape union = Shape.union(circle1, circle2);
      union = Shape.union(union, circle3);
      union.setFill(Color.RED);
      //Setting the stage
      Group root = new Group(circle1, circle2, circle3, union);
      Scene scene = new Scene(root, 595, 300);
      stage.setTitle("Union Operation");
      stage.setScene(scene);
      stage.show();
   }
   public static void main(String args[]){
      launch(args);
   }
}

Output