@Override
  public Class<?> getClassByName(String name) throws ClassNotFoundException {
    if (mutableConf != null) {
      Class<?> value = mutableConf.getClassByName(name);
      if (value != null) {
        return value;
      }
    }

    for (ImmutableConfigMap m : this.configs) {
      Class<?> value = m.getClassByName(name);
      if (value != null) {
        return value;
      }
    }
    throw new ClassNotFoundException();
  }
Add String map to config list. This map is generally created by HTableDescriptor or
HColumnDescriptor, but can be abstractly used. The added configuration overrides the previous
ones if there are name collisions.
@return this, for builder pattern
hbase-common/src/main/java/org/apache/hadoop/hbase/CompoundConfiguration.java