java.util.concurrent.ScheduledThreadPoolExecutor instances in which
corePoolSize is set to zero via the setCorePoolSize method or
the object constructor.
A ScheduledThreadPoolExecutor with zero core threads will run nothing.
Example:
void foo(int corePoolSize) {
if (corePoolSize != 0) return;
ThreadPoolExecutor executor = new ScheduledThreadPoolExecutor(corePoolSize); // warning
executor.setCorePoolSize(corePoolSize); // warning
}