TimerKlassen

TimerKlassen are a family of programming constructs that schedule the execution of code after a delay or at regular intervals. They are used to implement timeouts, periodic updates, animations, and delayed tasks. TimerKlassen can be implemented in two broad styles: thread-based timers that run a callback on a dedicated thread, and event-loop timers that enqueue tasks in a central event loop.

Key features typically include one-shot timers (firing once after a delay) and repeating timers (firing at a fixed interval), controls to start, stop, or reset the schedule, and the ability to cancel scheduled executions. Considerations include accuracy and drift caused by scheduler resolution and thread contention, as well as thread-safety and reentrancy. Many timer classes distinguish fixed-rate versus fixed-delay semantics for repeating tasks, and some provide cancellation tokens or disposal mechanisms to ensure resources are released.

Common implementations in popular languages illustrate the concept. Java provides java.util.Timer and TimerTask, where a Timer runs a background thread and tasks are scheduled with a delay or at a fixed rate. JavaScript environments offer setTimeout and setInterval, driven by the event loop. C# offers System.Timers.Timer and System.Threading.Timer, with properties such as Interval and AutoReset and corresponding events or callbacks. Python includes threading.Timer and the sched module, while GUI frameworks and platforms like Qt provide their own timer classes (for example, QTimer) that integrate with their event loops.

Limitations include timer resolution limits and potential jitter, especially on crowded or multi-tasking systems. Proper cleanup and cancellation are important to avoid leaks or unintended repeated executions.