apollo-client/src/main/java/com/ctrip/framework/apollo/internals/AbstractConfig.java/AbstractConfig/newCache
class AbstractConfig:  private <T> Cache<String, T> newCache() {
    Cache<String, T> cache = CacheBuilder.newBuilder()
        .maximumSize(m_configUtil.getMaxConfigCacheSize())
        .expireAfterAccess(m_configUtil.getConfigCacheExpireTime(), m_configUtil.getConfigCacheExpireTimeUnit())
        .build();
    allCaches.add(cache);
    return cache;
  }