What Happens if a Timer Task Throws an Exception in Java? — IT Interview Guide

Java’s class is a powerful tool for scheduling tasks at fixed-rate or fixed-delay intervals. While it’s convenient for performing repeated actions or scheduling a one-time task, it comes with some potential pitfalls, especially when it comes to error handling. Specifically, what happens when a TimerTask throws an exception during its execution?

In Java, when a TimerTask throws an uncaught exception, it has a significant effect on the Timer object. Typically, the exception is not propagated outside the task itself, but it can lead to some unexpected behaviors if not handled correctly. The task will be terminated, and depending on the nature of the exception, the Timer may continue or stop working entirely.

What Happens Internally?

The Timer class runs tasks in a single background thread. When a TimerTask throws an exception during its execution, the default behavior is that the exception is caught by the Timer itself. However, this will cause the task that threw the exception to be terminated. If the exception is thrown in a recurring task, the task will no longer be executed on subsequent intervals, which may not be the desired behavior in many cases.