private String getBodyAsString(byte[] body, Map<String, Collection<String>> headers) {
      Charset charset = getResponseCharset(headers);
      if (charset == null) {
        charset = Util.UTF_8;
      }
      return getResponseBody(body, charset);
    }
The Response body.

@return an Optional wrapping the response body.
core/src/main/java/feign/FeignException.java