Doesn't compile with opencv project?

Question

Java

As I just did not try to run an example from their site. Explain how to avoid such errors in the future and how to overcome this one. I have included the library here:

The compiler outputs this:

package sample;

import javafx.application.Application;
import javafx.fxml.FXMLLoader;
import javafx.scene.Parent;
import javafx.scene.Scene;
import javafx.stage.Stage;

import java.io.IOException;

public class Main extends Application {

    @Override
    public void start(Stage primaryStage) {
        Parent root = null;
        try {
            root = FXMLLoader.load(getClass().getResource("sample/sample.fxml"));
        } catch (IOException e) {
            e.printStackTrace();
        }
        primaryStage.setTitle("cv");
        primaryStage.setScene(new Scene(root, 400, 375));
        primaryStage.show();
    }


    public static void main(String[] args) {

        launch(args);
    }
}

package sample;

import javafx.event.ActionEvent;
import javafx.fxml.FXML;
import javafx.scene.control.Button;
import javafx.scene.image.ImageView;

public class Controller {

    static {
        System.load(opencvpath + org.opencv.core.Core.NATIVE_LIBRARY_NAME);
    }

    private  org.opencv.videoio.VideoCapture capture = new org.opencv.videoio.VideoCapture();

    @FXML
    private ImageView cameraFrame;

    @FXML
    private Button start_btn;

    @FXML
    void startCamera(ActionEvent event) {
    }



}

<?xml version="1.0" encoding="UTF-8"?>

<?import javafx.scene.image.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>


<BorderPane fx:controller="sample.Controller" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns:fx="http://javafx.com/fxml/1">
    <bottom>
        <Button fx:id="start_btn" mnemonicParsing="false" onAction="#startCamera" text="Start camera" BorderPane.alignment="CENTER" />
    </bottom>
    <center>
        <ImageView fx:id="cameraFrame" fitHeight="150.0" fitWidth="200.0" pickOnBounds="true" preserveRatio="true" BorderPane.alignment="CENTER" />
    </center>
</BorderPane>