protected String buildCacheKey(int x,int y,int z,String fileExt){
  return buildFilePath(x,y,z,fileExt);
}

protected String buildCacheKey ( int x , int y , int z , String fileExt ) { return buildFilePath ( x , y , z , fileExt ) ; }
creates a unique cache key for this tile based on zoom , x , y . this method was created so the servermaptilefactory could override it and use local cache names for keys if a local cache was being used .
