question: public void readOSM ( File file ) { if ( file . exists ( ) ) { streetLayer . openOSM ( file ) ; } else { LOG . info ( "osm.mapdb doesn't exist in graph folder. This means that street names won't be shown" ) ; } }
target:  Opens OSM MapDB database if it exists Otherwise it prints a warning OSM MapDB is used for names of streets. Since they are needed only in display of paths. They aren't saved in street layer.