public V get(K key) {
        final Map<K, V> map = ref != null ? ref.get() : null;
        return map != null ? map.get(key) : null;
    }
Gets a value from cache.
@param key the cache entry key
@return the cache entry value
standalone-metastore/metastore-common/src/main/java/org/apache/hadoop/hive/metastore/properties/SoftCache.java