Observable Animation Timer with JavaFX 8 and RxJava

Controller.java

package sample;

import javafx.animation.AnimationTimer;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;
import javafx.scene.paint.Color;
import rx.Observable;
import rx.subscriptions.Subscriptions;

import java.net.URL;
import java.util.ResourceBundle;

public class Controller implements Initializable {
    Observable<Long> timer ;

    @FXML
    Label label ;

    @Override
    public void initialize( URL url, ResourceBundle resourceBundle ) {
        timer = Observable.create( subscriber -> {
            final AnimationTimer timer = new AnimationTimer() {
                @Override
                public void handle( long l ) {
                    subscriber.onNext( l ) ;
                }
            } ;
            timer.start() ;
            return Subscriptions.create( () -> {
                timer.stop();
                subscriber.onCompleted() ;
            } ) ;
        } ) ;
        // Change the timer text
        timer.subscribe( time -> label.setText( Long.toString( time ) ) ) ;
        
        // And the color based on time
        timer.map( time -> (int)( time % 255 ) )
             .map( limited -> Color.rgb( limited, limited, limited ) )
             .subscribe( color -> label.setTextFill( color ) ) ;
    }
}

ControllerWithDeltas.java

// This version makes 2 Observables, one for system time and
// one for the deltas since last animation update
package sample;

import javafx.animation.AnimationTimer;
import javafx.fxml.FXML;
import javafx.fxml.Initializable;
import javafx.scene.control.Label;
import javafx.scene.paint.Color;
import rx.Observable;
import rx.subscriptions.Subscriptions;
import rx.util.functions.Func1;

import java.net.URL;
import java.util.ResourceBundle;

public class Controller implements Initializable {
    Observable<Long> timer ;
    Observable<Long> deltas ;

    @FXML
    Label label ;

    @Override
    public void initialize( URL url, ResourceBundle resourceBundle ) {
        // Make an Observable of the current system time from AnimationTimer
        timer = Observable.create( subscriber -> {
            final AnimationTimer timer = new AnimationTimer() {
                @Override
                public void handle( long time ) {
                    subscriber.onNext( time ) ;
                }
            } ;
            timer.start() ;
            return Subscriptions.create( () -> {
                timer.stop();
                subscriber.onCompleted() ;
            } ) ;
        } ) ;

        // And make an observable of the deltas based on this system time
        deltas = timer.map( new Func1<Long, Long>() {
            long previous = 0 ;
            @Override
            public Long call( Long time ) {
                long delta = time - previous ;
                previous = time ;
                return delta ;
            }
        } ) ;

        // Subscribe to timer to change the timer text
        timer.subscribe( time -> label.setText( Long.toString( time ) ) ) ;

        // And the color based on deltas
        deltas.map( time -> (int)( ( time / 1000 ) % 255 ) )
             .map( limited -> Color.rgb( limited, 0, 255 - limited ) )
             .subscribe( color -> label.setTextFill( color ) ) ;
    }
}