Redraw Circle in JavaFX

Hi all,

Having problems with redrawing circle in FX dependent on user input. Code compiles fine(no Syntax errors) but nothing renders.

Code:

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import javafx.application.Application;
import javafx.event.ActionEvent;
import javafx.event.EventHandler;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;
import javafx.scene.control.TextField;
import javafx.geometry.Pos;
import javafx.scene.text.Font;
import javafx.scene.shape.*;
import javafx.scene.Group;
import javafx.scene.control.Label;
import javafx.scene.layout.GridPane;
import javafx.geometry.HPos;
import java.util.Scanner;

public class PP4o15 extends Application {
    private Label result;
    private TextField input;
 
    public void start(Stage primaryStage) {
        int r;
        double pi= 3.14, area;
        Circle circle= new Circle(100,65,20);
        circle.setFill(null);
     
       
        Scanner q = new Scanner(System.in);
        r=q.nextInt();
        //Pi Method
        area=pi*r*r;
     
 
        Font font= new Font(18);
        input= new TextField();
        //Changed Font below
        input.setFont(new Font("Arial",30));
        input.setPrefWidth(50);
        input.setAlignment(Pos.CENTER);
       
        //Stacking input TextField ontop of circle
        //StackPane pane= new StackPane(circle);
        //pane.getChildren().addAll(circle,input);
       
        Group root= new Group(circle);
        Scene scene= new Scene(root,400,200);
       
        result = new Label("");
        result.setFont(font);
        GridPane.setHalignment(result,HPos.CENTER);
       
        primaryStage.setTitle("Enter in Radius");
        primaryStage.setScene(scene);
        primaryStage.show();
    }
    //Create method that has return
    public void processReturn(ActionEvent event)
    {
      //Method to process return
        input.setOnAction(this::processReturn);
    }
}

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