code: public static boolean isAbsoluteURI( String uri )
      {
           //
           // This method needs to be fast, so it can't use java.net.URI.
           //
           if ( uri.length() == 0 || uri.charAt( 0 ) == '/' ) return false;
          
           for ( int i = 0, len = uri.length(); i < len; ++i )
           {
               char c = uri.charAt( i );
              
               if ( c == ':' )
               {
                   return true;
               }
               else if ( c == '/' )
               {
                   return false;
               }
           }
          
           return false;
       }
docs: This is the same logic that we have in the runtime, in PageFlowRequestProcessor.  Can't share the code, though.