Can't increase ThreadPoolExecutor's core pool size I'm having issues dynamically increasing the core pool size of a ThreadPoolExecutor in kotlin. First I define my ThreadPoolExecutor like this: val POOL = Executors.newFixedThreadPool(20) as ThreadPoolExecutor Then I add some tasks to the ThreadPoolExecutor. After some time, in a different thread, while the tasks are still running: POOL.corePoolSize += 20 It returns: Exception in thread "Thread-0" java.lang.IllegalArgumentException at...