Updating UI from not FX Thread

/**
 * in MainLayoutController.java
 * calling download method in Task<> in new Thread
 */

final int buffer = 10000; // On my hardware no more makes sense

Downloader.setController(this);
Task<Void> downloadTask = new Task<Void>() {
    @Override
    protected Void call() throws Exception {
        Downloader.downloadFile(URL, PATH, buffer);

        return null;
    }
};
new Thread(downloadTask).start();


/**
 * Downloader.java
 */

package com.ddownloader.util;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.math.BigDecimal;
import java.net.HttpURLConnection;
import java.net.URL;

import com.ddownloader.view.MainLayoutController;

import javafx.application.Platform;

public class Downloader {
    private static MainLayoutController mlController;

    public static void setController(MainLayoutController c) {
        mlController = c;
    }

    public static void downloadFile(String url, String savePath, int buffSize) {
        try {
            /* Get connection */
            URL connection = new URL(url);
            HttpURLConnection urlconn;
            long size;

            urlconn = (HttpURLConnection) connection.openConnection();
            urlconn.setRequestMethod("GET");
            size = urlconn.getContentLengthLong();
            urlconn.connect();

            /* Set input stream */
            InputStream in = null;

            try {
                in = urlconn.getInputStream();
            }
            catch (IOException e) {
                Platform.runLater(() -> mlController.throwAlert(e.getMessage()));
                mlController.doneQuantity++;
                Platform.runLater(() ->
                mlController.downloadedLabel.setText(mlController.doneQuantity + "/" + mlController.quantity)
                );
                Platform.runLater(() ->
                    mlController.updateDownloadedPB((1.0 / mlController.quantity) * mlController.doneQuantity)
                );
                Platform.runLater(() -> mlController.downloadingLabel.setText("Done"));
                Platform.runLater(() -> mlController.sizeLabel.setText("Size:"));
                Platform.runLater(() -> mlController.speedLabel.setText("Speed:"));
                return;
            }

            /* Find file full path */
            String[] tempArr = url.split("/");

            String fullPath = savePath + tempArr[tempArr.length - 1];

            /* Set Labels */
            Platform.runLater(() -> mlController.downloadingLabel.setText(tempArr[tempArr.length - 1]));
            Platform.runLater(() -> mlController.downloadingPB.setProgress(0.0));

            Platform.runLater(() ->
                mlController.downloadedLabel.setText(mlController.doneQuantity + "/" + mlController.quantity)
            );
            if (mlController.doneQuantity == 0) Platform.runLater(() -> mlController.downloadedPB.setProgress(0.0));

            Double dTemp = new BigDecimal(size / Math.pow(10, 6))
                    .setScale(3, BigDecimal.ROUND_HALF_UP)
                    .doubleValue();
            Platform.runLater(() -> mlController.sizeLabel.setText("Size: " + dTemp + " Mb"));

            /* Set write stream */
            OutputStream writer = new FileOutputStream(fullPath);
            byte buffer[] = new byte[buffSize]; // Max bytes per one reception

            /* Download */
            int i = 0;
            long i_sum = 0;
            long delta_t = System.nanoTime();
            double getted_b = 0.0;

            while ((i = in.read(buffer)) > 0) {
                writer.write(buffer, 0, i);
                getted_b += i;
                i_sum += i;

                mlController.updateDownloadingPB(size, i_sum); // with method cause lambda needs final values

                if ((System.nanoTime() - delta_t) >= 1E9) { // If the second was over
                    Double speed = new BigDecimal(getted_b / Math.pow(10, 6))
                            .setScale(3, BigDecimal.ROUND_HALF_UP)
                            .doubleValue();

                    Platform.runLater(() -> mlController.speedLabel.setText("Speed: " + speed + " Mb/s"));

                    delta_t = System.nanoTime(); // Set to zero
                    getted_b = 0.0;
                }
                if (size == i_sum) { // ==> Download is complete
                    mlController.doneQuantity++;

                    Platform.runLater(() ->
                        mlController.downloadedLabel.setText(mlController.doneQuantity + "/" + mlController.quantity)
                    );
                    Platform.runLater(() ->
                        mlController.updateDownloadedPB((1.0 / mlController.quantity) * mlController.doneQuantity)
                    );

                    Platform.runLater(() -> mlController.downloadingLabel.setText("Done"));
                    Platform.runLater(() -> mlController.sizeLabel.setText("Size:"));
                    Platform.runLater(() -> mlController.speedLabel.setText("Speed:"));
                }
            }

            /* Cleaning */
            writer.flush();
            writer.close();
            in.close();
        } catch (IOException e) {
            System.out.println(e);
        }
    }
}