Demo of selection of Nodes by mouse click in JavaFx

MyCircle.java

import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;

public class MyCircle extends Circle implements SelectableNode {
	public MyCircle(double centerX, double centerY, double radius) {
		super(centerX, centerY, radius);
	}

	@Override
	public boolean requestSelection(boolean select) {
		return true;
	}

	@Override
	public void notifySelection(boolean select) {
		if(select)
			this.setFill(Color.RED);
		else
			this.setFill(Color.BLACK);
	}
}

SelectableNode.java

/**
 * This interface is based on jfxtras-labs <a href="https://github.com/JFXtras/jfxtras-labs/blob/8.0/src/main/java/jfxtras/labs/scene/control/window/SelectableNode.java">SelectableNode</a>
 */
public interface SelectableNode {
	public boolean requestSelection(boolean select);
	
	public void notifySelection(boolean select);
}

SelectionDemo.java

import javafx.application.Application;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.scene.input.MouseEvent;
import javafx.scene.layout.BorderPane;
import javafx.stage.Stage;

public class SelectionDemo extends Application {
    @Override
    public void start(Stage primaryStage) {
        Scene scene = new Scene(createPane(), 400, 400);
        primaryStage.setScene(scene);
        primaryStage.show();
    }
    
    private Parent createPane() {
    	BorderPane root = new BorderPane();
    	SelectionHandler selectionHandler = new SelectionHandler(root);
    	root.addEventHandler(MouseEvent.MOUSE_PRESSED, selectionHandler.getMousePressedEventHandler());
    	
    	MyCircle c1 = new MyCircle(40, 40, 20);
        MyCircle c2 = new MyCircle(40, 100, 20);
        MyCircle c3 = new MyCircle(40, 160, 20);
        root.getChildren().addAll(c1, c2, c3);

        return root;
    }

    public static void main(String[] args) {
        launch(args);
    }
}

SelectionHandler.java

import java.util.ArrayList;
import java.util.List;

import javafx.collections.FXCollections;
import javafx.collections.ObservableList;
import javafx.event.EventHandler;
import javafx.scene.Node;
import javafx.scene.Parent;
import javafx.scene.input.MouseEvent;

public class SelectionHandler {
	private Clipboard clipboard;
	
	private EventHandler<MouseEvent> mousePressedEventHandler;
	
	public SelectionHandler(final Parent root) {
		this.clipboard = new Clipboard();
		this.mousePressedEventHandler = new EventHandler<MouseEvent>() {
			@Override
			public void handle(MouseEvent event) {
				SelectionHandler.this.doOnMousePressed(root, event);
				event.consume();
			}
		};
	}
	
	public EventHandler<MouseEvent> getMousePressedEventHandler() {
		return mousePressedEventHandler;
	}
	
	private void doOnMousePressed(Parent root, MouseEvent event) {
		Node target = (Node) event.getTarget();
		if(target.equals(root))
			clipboard.unselectAll();
		if(root.getChildrenUnmodifiable().contains(target) && target instanceof SelectableNode) {
			SelectableNode selectableTarget = (SelectableNode) target;
			if(!clipboard.getSelectedItems().contains(selectableTarget))
				clipboard.unselectAll();
			clipboard.select(selectableTarget, true);
		}
	}
	
	/**
	 * This class is based on jfxtras-labs
	 *  <a href="https://github.com/JFXtras/jfxtras-labs/blob/8.0/src/main/java/jfxtras/labs/scene/control/window/Clipboard.java">Clipboard</a>
	 *  and 
	 *  <a href="https://github.com/JFXtras/jfxtras-labs/blob/8.0/src/main/java/jfxtras/labs/util/WindowUtil.java">WindowUtil</a>
	 */
	private class Clipboard {
		private ObservableList<SelectableNode> selectedItems = FXCollections.observableArrayList();

		public ObservableList<SelectableNode> getSelectedItems() {
			return selectedItems;
		}

		public boolean select(SelectableNode n, boolean selected) {
			if(n.requestSelection(selected)) {
				if (selected) {
					selectedItems.add(n);
				} else {
					selectedItems.remove(n);
				}
				n.notifySelection(selected);
				return true;
			} else {
				return false;
			}
		}

		public void unselectAll() {
			List<SelectableNode> unselectList = new ArrayList<>();
			unselectList.addAll(selectedItems);

			for (SelectableNode sN : unselectList) {
				select(sN, false);
			}
		}
	}
}