public abstract class AbstractDatabaseManager extends OrmLiteSqliteOpenHelper {

    private static final Map<Class<? extends AbstractDatabaseManager>, AtomicInteger> sUsageCounters = new HashMap<Class<? extends AbstractDatabaseManager>, AtomicInteger>();
    private static final Map<Class<? extends AbstractDatabaseManager>, AbstractDatabaseManager> sInstances = new HashMap<Class<? extends AbstractDatabaseManager>, AbstractDatabaseManager>();

    protected Context mContext;

    public static <T extends AbstractDatabaseManager> T getHelper(Class<T> clazz, Context context) {
        synchronized (clazz) {
            if (!sInstances.containsKey(clazz)) {
                try {
                    Constructor<T> constructor = clazz.getConstructor(Context.class);
                    T instance = constructor.newInstance(context);
                    sInstances.put(clazz, instance);
                } catch (ReflectiveOperationException e) {
                    return null;
                } catch (IllegalArgumentException e) {
                    return null;
                }
            }
            if (!sUsageCounters.containsKey(clazz)) {
                sUsageCounters.put(clazz, new AtomicInteger(0));
            }
            sUsageCounters.get(clazz).incrementAndGet();
            return cast(sInstances.get(clazz));
        }
    }

    @Override
    public void close() {
        if (sUsageCounters.get(getClass()).decrementAndGet() == 0) {
            super.close();
            sInstances.remove(getClass());
            mContext = null;
        }
    }
}