code: @Nonnull
      public String createNewSessionId( @Nonnull final String sessionId, @Nonnull final String newMemcachedId) {
          final int idxDot = sessionId.indexOf( '.' );
          if ( idxDot != -1 ) {
              final String plainSessionId = sessionId.substring( 0, idxDot );
              final String jvmRouteWithDot = sessionId.substring( idxDot );
              return appendOrReplaceMemcachedId( plainSessionId, newMemcachedId ) + jvmRouteWithDot;
          }
          else {
              return appendOrReplaceMemcachedId( sessionId, newMemcachedId );
          }
      }
docs: Change the provided session id (optionally already including a memcachedId) so that it
  contains the provided newMemcachedId.
  
  @param sessionId
  the session id that may contain a former memcachedId.
  @param newMemcachedId
  the new memcached id.
  @return the sessionId which now contains the new memcachedId instead the
  former one.