code: public static String getPrefixedUri(String prefix, String uri) {
          String localURI = uri;
          if (localURI.length() > 0) {
              // Put a / between the prefix and the tail only if:
              // the prefix does not ends with a /
              // the tail does not start with a /
              // the tail starts with an alphanumeric character.
              if (!localURI.startsWith("/")
                      && !prefix.endsWith("/")
                      && Character.isLetterOrDigit(localURI.indexOf(0))) {
                  localURI = prefix + "/" + localURI;
              } else {
                  localURI = prefix + localURI;
              }
          } else {
              // Empty tail, just return the prefix.
              return prefix;
          }
          return localURI;
      }
docs: Prepends the given prefix to the given uri.
  
  @param prefix the prefix
  @param uri    the uri
  @return the full uri