How to update the label box every 2 seconds in java fx?

To solve your task using Timer you need to implement TimerTask with your code and use Timer#scheduleAtFixedRate method to run that code repeatedly:

Timer timer = new Timer();
    timer.scheduleAtFixedRate(new TimerTask() {
        @Override
        public void run() {
            System.out.print("I would be called every 2 seconds");
        }
    }, 0, 2000);

Also note that calling any UI operations must be done on Swing UI thread (or FX UI thread if you are using JavaFX):

private int i = 0;
private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) {
    Timer timer = new Timer();
    timer.scheduleAtFixedRate(new TimerTask() {
        @Override
        public void run() {
            SwingUtilities.invokeLater(new Runnable() {
                @Override
                public void run() {
                    jTextField1.setText(Integer.toString(i++));
                }
            });
        }
    }, 0, 2000);
}

In case of JavaFX you need to update FX controls on "FX UI thread" instead of Swing one. To achieve that use javafx.application.Platform#runLater method instead of SwingUtilities

Here is an alternate solution which uses a JavaFX animation Timeline instead of a Timer.

I like this solution because the animation framework ensures that everything happens on the JavaFX application thread, so you don't need to worry about threading issues.

import javafx.animation.*;
import javafx.application.Application;
import javafx.beans.binding.Bindings;
import javafx.beans.property.*;
import javafx.event.*;
import javafx.scene.*;
import javafx.scene.control.*;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;
import javafx.util.Duration;

import java.util.Random;

public class ThermostatApp extends Application {
  @Override public void start(final Stage stage) throws Exception {
    final Thermostat       thermostat       = new Thermostat();
    final TemperatureLabel temperatureLabel = new TemperatureLabel(thermostat);

    VBox layout = new VBox(10);
    layout.getChildren().addAll(temperatureLabel);
    layout.setStyle("-fx-background-color: cornsilk; -fx-padding: 20; -fx-font-size: 20;");

    stage.setScene(new Scene(layout));
    stage.show();
  }

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

class TemperatureLabel extends Label {
  public TemperatureLabel(final Thermostat thermostat) {
    textProperty().bind(
      Bindings.format(
        "%3d \u00B0F",
        thermostat.temperatureProperty()
      )
    );
  }
}

class Thermostat {
  private static final Duration PROBE_FREQUENCY = Duration.seconds(2);

  private final ReadOnlyIntegerWrapper temperature;
  private final TemperatureProbe       probe;
  private final Timeline               timeline;

  public ReadOnlyIntegerProperty temperatureProperty() {
    return temperature.getReadOnlyProperty();
  }

  public Thermostat() {
    probe       = new TemperatureProbe();
    temperature = new ReadOnlyIntegerWrapper(probe.readTemperature());

    timeline = new Timeline(
        new KeyFrame(
          Duration.ZERO,
          new EventHandler<ActionEvent>() {
            @Override public void handle(ActionEvent actionEvent) {
              temperature.set(probe.readTemperature());
            }
          }
        ),
        new KeyFrame(
          PROBE_FREQUENCY
        )
    );
    timeline.setCycleCount(Timeline.INDEFINITE);
    timeline.play();
  }
}

class TemperatureProbe {
  private static final Random random = new Random();

  public int readTemperature() {
    return 72 + random.nextInt(6);
  }
}

The solution is based upon the countdown timer solution from: JavaFX: How to bind two values?