Trying to implement a coding solution for a programming project, below is what the output should be:

Specifically, the relavant goal in non-picture form is:

 A private event handler that handles mouse clicks that adds a point with a left click,
removes a point with a right click and recomputes the maximal point set afterward

 A private method that finds the maximal set and draws the lines that connect them

My implementation (or where I’ve narrowed down the errors):

public class PointPane extends Pane {

private final ArrayList<Point> points;

public PointPane(ArrayList<Point> points) {
    
    this.points = points;
    drawPoints();
    
    this.setOnMouseClicked(this::handleMouseClick);
}

// this is the section with the first issue

private void handleMouseClick(MouseEvent event) {

    // after entry it should be checking for the left or right mouse button, but
    // it does not enter either the if or the else if and goes directly to
    // drawPoints();

    if (event.isPrimaryButtonDown()) { // Left click
        points.add(new Point(event.getX(), event.getY()));

    } else if (event.isSecondaryButtonDown()) { // Right click            
        Point pointToRemove = null;

        for (Point point : points) {
            if (Math.abs(point.getX() - event.getX()) 
                    < 5 && Math.abs(point.getY() - event.getY()) < 5) {
                pointToRemove = point;
                break;
            }
        }

        if (pointToRemove != null) {
            points.remove(pointToRemove);
        }
    }
    drawPoints();
}

private void drawPoints() {

    this.getChildren().clear();

    for (Point point : points) {
        
        javafx.scene.shape.Circle circle = 
            new javafx.scene.shape.Circle(
            point.getX(), point.getY(), 5);

        this.getChildren().add(circle);
    }

    findAndDrawMaximalSet();
}

… // This is the second issue

private void findAndDrawMaximalSet() {
    ArrayList<Point> maximalSet = new ArrayList<>();
    for (Point point : points) {
        boolean isMaximal = true;
        for (Point other : points) {
            if (point != other && point.isBelowAndToLeftOf(other)) {
                isMaximal = false;
                break;
            }
        }
        if (isMaximal) {
            maximalSet.add(point);
        }
    }
    if (maximalSet.size() >= 2) {
        Collections.sort(maximalSet);
        drawLines(maximalSet);
    }
}

private void drawLines(ArrayList<Point> maximalSet) {
    
    this.getChildren().removeIf(node -> node instanceof Line);

    if (maximalSet.size() >= 2) {
        for (int i = 0; i < maximalSet.size() - 1; i++) {
            Point p1 = maximalSet.get(i);
            Point p2 = maximalSet.get(i + 1);
            Line line = new Line(p1.getX(), p1.getY(), 
            p2.getX(), p2.getY());
            this.getChildren().add(line);
        }
    }
}

}