question: private static String quadTree ( final MapTile aTile ) { StringBuilder quadKey = new StringBuilder ( ) ; for ( int i = aTile . zoomLevel ; i > 0 ; i -- ) { int digit = 0 ; int mask = 1 << ( i - 1 ) ; if ( ( aTile . x & mask ) != 0 ) digit += 1 ; if ( ( aTile . y & mask ) != 0 ) digit += 2 ; quadKey . append ( digit ) ; } return quadKey . toString ( ) ; }
target:  Converts TMS tile coordinates to QuadTree