code: public static Map<String, CharSequence> extractFacebookParamsFromArray(Map<CharSequence, CharSequence[]> reqParams) {
      if (null == reqParams)
        return null;
      Map<String,CharSequence> result = new HashMap<String,CharSequence>(reqParams.size());
      for (Map.Entry<CharSequence,CharSequence[]> entry : reqParams.entrySet()) {
        String key = entry.getKey().toString();
        if (FacebookParam.isInNamespace(key)) {
          CharSequence[] value = entry.getValue();
          if (value.length > 0)
            result.put(key, value[0]);
        }
      }
      return result;
    }
docs: Out of the passed in <code>reqParams</code>, extracts the parameters that
  are in the FacebookParam namespace and returns them.
  @param reqParams A map of request parameters to their values. Values
  are arrays of strings, as returned by
  ServletRequest.getParameterMap(). Only the first element
  in a given array is significant.
  @return a boolean indicating whether the calculated signature matched the
  expected signature