What happens to an exception thrown inside a pooled task?

This asymmetry swallows more bugs than any other part of the API. execute(Runnable) lets the exception propagate: the thread's UncaughtExceptionHandler runs (by default printing to stderr) and ThreadPoolExecutor quietly replaces the dead worker.

submit wraps the task in a FutureTask, which catches everything and stores it. No log line, no handler, nothing, until someone calls get() and receives an ExecutionException. A fire-and-forget submit whose Future is discarded loses failures completely.

Defences: wrap task bodies in try/catch, override afterExecute to inspect both paths, or use CompletableFuture with whenComplete. For scheduled tasks it is worse, see the next question.