code: protected void setURI() {
          if (_scheme != null) {
              if (_scheme.length == 4 && Arrays.equals(_scheme, HTTP_SCHEME)) {
                  _scheme = HTTP_SCHEME;
              } else if (_scheme.length == 5
                      && Arrays.equals(_scheme, HTTPS_SCHEME)) {
                  _scheme = HTTPS_SCHEME;
              }
          }
          super.setURI();
      }
docs: Coalesce _scheme to existing instances, where appropriate.
  
  In the web-crawl domain, most _schemes are 'http' or 'https',
  but the superclass always creates a new char[] instance. For
  these two cases, we replace the created instance with a
  long-lived instance from a static field, saving 12-14 bytes
  per instance.
  
  @see org.apache.commons.httpclient.URI#setURI()