src/main/java/io/reactivex/internal/schedulers/SchedulerPoolFactory.java
public static void shutdown() {
        ScheduledExecutorService exec = PURGE_THREAD.getAndSet(null);
        if (exec != null) {
            exec.shutdownNow();
        }
        POOLS.clear();
    }
public static void shutdown() {
        ScheduledExecutorService exec = PURGE_THREAD.getAndSet(null);
        if (exec != null) {
            exec.shutdownNow();
        }
        POOLS.clear();
    }
Stops the purge thread.