protected void startReloadThread() {
        if (this.reloadIntervalSeconds > 0) {
            this.scheduler = Executors.newSingleThreadScheduledExecutor();
            ((ScheduledExecutorService) this.scheduler)
                    .scheduleAtFixedRate(this, reloadIntervalSeconds, reloadIntervalSeconds, TimeUnit.SECONDS);
        }
    }
Destroy reload scheduler if one exists.
core/src/main/java/org/apache/shiro/realm/text/PropertiesRealm.java