import javafx.application.Application;

import javafx.event.ActionEvent;

import javafx.event.EventHandler;

import javafx.geometry.Pos;

import javafx.scene.Scene;

import javafx.scene.control.Button;

import javafx.scene.layout.BorderPane;

import javafx.scene.layout.HBox;

import javafx.scene.layout.StackPane;

import javafx.scene.paint.Color;

import javafx.scene.shape.Circle;

import javafx.stage.Stage;

public class ControlCircle extends Application {

private CirclePane circlePane = new CirclePane();

@Override

public void start(Stage primaryStage) throws Exception {

HBox hBox = new HBox();

hBox.setSpacing(10);

hBox.setAlignment(Pos.CENTER);

Button btEnlarge = new Button("Enlarge");

Button btShrink = new Button("Shrink");

hBox.getChildren().add(btEnlarge);

hBox.getChildren().add(btShrink);

btEnlarge.setOnAction(new EnlargeHandler());

btShrink.setOnAction(new ShrinkHandler());

BorderPane borderPane = new BorderPane();

borderPane.setCenter(circlePane);

borderPane.setBottom(hBox);

BorderPane.setAlignment(hBox, Pos.CENTER);

Scene scene = new Scene(borderPane, 200, 150);

primaryStage.setScene(scene);

primaryStage.show();

}

class EnlargeHandler implements EventHandler<ActionEvent> {

@Override

public void handle(ActionEvent event) {

circlePane.enlarge();

}

}

class ShrinkHandler implements EventHandler<ActionEvent> {

@Override

public void handle(ActionEvent event) {

circlePane.shrink();

}

}

}

class CirclePane extends StackPane {

private Circle circle = new Circle(50);

public CirclePane() {

getChildren().add(circle);

circle.setStroke(Color.BLACK);

circle.setFill(Color.YELLOWGREEN);

}

public void enlarge() {

circle.setRadius(circle.getRadius() + 2);

}

public void shrink () {

circle.setRadius(circle.getRadius() > 2 ? circle.getRadius() - 2 : circle.getRadius());

}

}