private void onEmptyBuckets(List<BucketId> bucketIds) {
            StringBuilder buckets = new StringBuilder();
            for(BucketId bid : bucketIds) {
                buckets.append(" ");
                buckets.append(bid.toString());
            }
            log.log(Level.INFO, "Got EmptyBuckets: " + buckets);
        }
A visitor data and progress handler that writes to STDOUT.

Due to java not being able to inherit two classes, and neither being an
interface this had to be implemented by creating a wrapper class.

@author Thomas Gundersen
vespaclient-java/src/main/java/com/yahoo/vespavisit/StdOutVisitorHandler.java