@Override
    public void close() {
        for (PhysicalFile f : fileCache.values()) {
            if (f != null) {
                f.close();
            }
        }
    }
get a node for the given id with all link-targets also non-hollow
<p>
It is required that an instance of the start-node does not yet
exist, not even a hollow instance, so getStartNode should only
be called once right after resetting the cache

@param id the id of the node to load
@return the fully expanded node for id, or null if it was not found
main/src/main/java/cgeo/geocaching/brouter/mapaccess/NodesCache.java