apollo-client/src/main/java/com/ctrip/framework/apollo/internals/AbstractConfig.java/AbstractConfig/getFloatProperty
class AbstractConfig:  @Override
  public Float getFloatProperty(String key, Float defaultValue) {
    try {
      if (m_floatCache == null) {
        synchronized (this) {
          if (m_floatCache == null) {
            m_floatCache = newCache();
          }
        }
      }

      return getValueFromCache(key, Functions.TO_FLOAT_FUNCTION, m_floatCache, defaultValue);
    } catch (Throwable ex) {
      Tracer.logError(new ApolloConfigException(
          String.format("getFloatProperty for %s failed, return default value %f", key,
              defaultValue), ex));
    }
    return defaultValue;
  }