public synchronized Set<String> getInViewport(final Viewport viewport) {
        final Set<String> geocodes = new HashSet<>();
        for (final Geocache cache : cachesCache.values()) {
            if (cache.getCoords() == null) {
                // FIXME: this kludge must be removed, it is only present to help us debug the cases where
                // caches contain null coordinates.
                Log.w("CacheCache.getInViewport: got cache with null coordinates: " + cache.getGeocode());
                continue;
            }
            if (viewport.contains(cache)) {
                geocodes.add(cache.getGeocode());
            }
        }
        return geocodes;
    }
@param geocode Geocode of the cache to retrieve from the cache
@return cache if found, null else
main/src/main/java/cgeo/geocaching/storage/CacheCache.java