common_helper/src/main/java/com/xiongyingqi/util/WeakReferenceMonitor.java
private static boolean keepMonitoringThreadAlive() {
        synchronized (WeakReferenceMonitor.class) {
            if (!trackedEntries.isEmpty()) {
                return true;
            } else {
                logger.debug("No entries left to track - stopping reference monitor thread");
                monitoringThread = null;
                return false;
            }
        }
    }
private static boolean keepMonitoringThreadAlive() {
        synchronized (WeakReferenceMonitor.class) {
            if (!trackedEntries.isEmpty()) {
                return true;
            } else {
                logger.debug("No entries left to track - stopping reference monitor thread");
                monitoringThread = null;
                return false;
            }
        }
    }
Check whether to keep the monitoring thread alive,
i.e. whether there are still entries being tracked.