How to bounce 2 shapes concurrently in JAVAFX with avoiding collision?

import javafx.animation.KeyFrame;
import javafx.animation.KeyValue;
import javafx.animation.Timeline;
import javafx.application.Application;
import javafx.geometry.Bounds;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.layout.Border;
import javafx.scene.layout.BorderStroke;
import javafx.scene.layout.BorderStrokeStyle;
import javafx.scene.layout.BorderWidths;
import javafx.scene.layout.CornerRadii;
import javafx.scene.layout.Pane;
import javafx.scene.paint.Color;
import javafx.scene.shape.Circle;
import javafx.scene.shape.Rectangle;
import javafx.scene.shape.Shape;
import javafx.stage.Stage;
import javafx.util.Duration;

public class ShapeTest extends Application {

    @Override
    public void start(Stage stage) {

        Pane pane = new Pane();
        Scene scene = new Scene(pane, 300, 300);

        //=======================================================================
        // CAR 1
        // create the car body
        Rectangle body = new Rectangle(150, 50, 100, 50);
        body.setFill(Color.RED);

        // create the wheels
        Circle wheel1 = new Circle(175, 100, 15);
        Circle wheel2 = new Circle(225, 100, 15);

        // create the car roof
        Rectangle roof = new Rectangle(160, 30, 80, 20);
        roof.setFill(Color.DARKBLUE);

        // create the windows
        Rectangle window1 = new Rectangle(170, 35, 25, 15);
        Rectangle window2 = new Rectangle(205, 35, 25, 15);
        Shape windows = Shape.union(window1, window2);
        windows.setFill(Color.LIGHTBLUE);

        // create the car group and add the shapes to it
        Group carGroup = new Group();
        carGroup.getChildren().addAll(body, wheel1, wheel2, roof, windows);
        carGroup.setLayoutX(5); // initial X position
        carGroup.setLayoutY(5); // initial Y position

        // add the car group to the pane
        pane.getChildren().add(carGroup);

        pane.setBorder(new Border(new BorderStroke(Color.RED,
                BorderStrokeStyle.SOLID, CornerRadii.EMPTY, BorderWidths.DEFAULT)));

        carGroup.relocate(5, 5);

        // move the carGroup along the X axis
        KeyValue kvX = new KeyValue(carGroup.layoutXProperty(), pane.getWidth() - pane.getBorder().getInsets().getRight() - carGroup.getBoundsInLocal().getMaxX());
        KeyFrame kfX = new KeyFrame(Duration.seconds(1), kvX);
        Timeline timelineX = new Timeline(kfX);
        timelineX.setCycleCount(Timeline.INDEFINITE);

        // move the carGroup along the Y axis
        KeyValue kvY = new KeyValue(carGroup.layoutYProperty(), pane.getHeight() - pane.getBorder().getInsets().getBottom() - carGroup.getBoundsInLocal().getMaxY());
        KeyFrame kfY = new KeyFrame(Duration.seconds(1), kvY);
        Timeline timelineY = new Timeline(kfY);
        timelineY.setCycleCount(Timeline.INDEFINITE);

        timelineX.play();
        timelineY.play();

        //=======================================================================
        // CAR 2
        // create the car body
        Rectangle body1 = new Rectangle(150, 50, 100, 50);
        body1.setFill(Color.YELLOW);

        // create the wheels
        Circle wheel11 = new Circle(175, 100, 15);
        Circle wheel22 = new Circle(225, 100, 15);

        // create the car roof
        Rectangle roof1 = new Rectangle(160, 30, 80, 20);
        roof1.setFill(Color.CYAN);

        // create the windows
        Rectangle window11 = new Rectangle(170, 35, 25, 15);
        Rectangle window22 = new Rectangle(205, 35, 25, 15);
        Shape windows1 = Shape.union(window11, window22);
        windows1.setFill(Color.PINK);

        // create the car group and add the shapes to it
        Group carGroup1 = new Group();
        carGroup1.getChildren().addAll(body1, wheel11, wheel22, roof1, windows1);
        carGroup1.setLayoutX(5); // initial X position
        carGroup1.setLayoutY(5); // initial Y position

        // add the car group to the pane
        pane.getChildren().add(carGroup1);

        carGroup1.relocate(20, 20);

        // move the carGroup along the X axis
        KeyValue kvX1 = new KeyValue(carGroup1.layoutXProperty(), pane.getWidth() - pane.getBorder().getInsets().getRight() - carGroup1.getBoundsInLocal().getMaxX());
        KeyFrame kfX1 = new KeyFrame(Duration.seconds(1), kvX1);
        Timeline timelineX1 = new Timeline(kfX);
        timelineX1.setCycleCount(Timeline.INDEFINITE);

        // move the carGroup along the Y axis
        KeyValue kvY1 = new KeyValue(carGroup1.layoutYProperty(), pane.getHeight() - pane.getBorder().getInsets().getBottom() - carGroup1.getBoundsInLocal().getMaxY());
        KeyFrame kfY1 = new KeyFrame(Duration.seconds(1), kvY1);
        Timeline timelineY1 = new Timeline(kfY1);
        timelineY1.setCycleCount(Timeline.INDEFINITE);

        timelineX1.play();
        timelineY1.play();

        //=======================================================================
        // set the stage properties and show it
        stage.setTitle("Moving Cars");
        stage.setScene(scene);
        stage.show();
    }

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