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Interval

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24.02
Java API

The Interval class represents a timer that triggers an event with a fixed time delay between each triggering.

You can start, stop, and restart an Interval as needed and add multiple listeners for the elapsed event. In webforJ, an Interval has better performance compared to a standard Java timer or Swing timer.

Usages​

The Interval class triggers events at a fixed time delay. By using Intervals creatively, you can create dynamic and interesting experiences in your app:

  1. Check for Inactivity: Display a Dialog component if there hasn't been any interaction on a form within a given time.

  2. Featured Content: Rotate through featured articles, products, or promotions on your homepage on each Interval. This keeps the content dynamic and engaging.

  3. Live Data: Refresh data on your app, such as stock prices, news feeds, or weather updates, on each Interval to keep the data current.

Managing Interval states: starting, stopping, and restart​

An Interval requires manual activation; use the start() method to initiate it. To stop an Interval, use the stop() method. The restart() method can be used to restart the Interval.

Adjusting the Interval delay​

To modify the delay of an Interval, use the setDelay(float delay) method. The new delay value is applied after the Interval is either stopped or restarted.

//Changing the Delay
Interval.setDelay(2f);
Interval.restart();
tip

The delay can be fractional seconds to millisecond in resolution, but a very small timeout value causes a flood of events faster than the program can respond to them.

Adding listeners​

You can attach additional listeners to an Interval using the addElapsedListener(EventListener\<Interval.ElapsedEvent\> listener) method. Once a listener is added, it automatically triggers on the next interval if the Interval is already running.

// Adding Listeners
float dealy = 2f;

EventListener<Interval.ElapsedEvent> firstListener = (e -> {
// Executable code
});

Interval interval = new Interval(delay, firstListener);

EventListener<Interval.ElapsedEvent> secondListener = (e -> {
// Executable code
});

interval.addElapsedListener(secondListener);

Performance​

The Interval class is specifically designed to provide better performance and reliability for the large loads encountered by web apps. In Java Swing, the same behavior can be sufficiently managed by a Timer or a new thread, but that approach doesn't scale well for web apps. Web apps are likely to have many concurrent users, and if each user creates a new Timer or thread, the system can quickly break when it runs out of threads.

There are several viable options that work at this scale: virtual threads, Spring TaskExecutor and TaskScheduler, and Interval. Depending on your app and use-case, any of these may be the best option for you. As a default, Interval is a reliable choice specifically designed to work with webforJ, and requires no additional configuration.