You can list the keys for the bucket and call delete for each. Or if you put the keys (and kept track of them in your test) you can delete them one at a time (without incurring the cost of calling list first.)
Something like:
String bucket = "my_bucket"; BucketResponse bucketResponse = riakClient.listBucket(bucket); RiakBucketInfo bucketInfo = bucketResponse.getBucketInfo(); for(String key : bucketInfo.getKeys()) { riakClient.delete(bucket, key); }
would do it.
See also
http://wiki.basho.com/REST-API.html#Bucket-operations
which says
"At the moment there is no straightforward way to delete an entire
Bucket. There is, however, an open ticket for the feature. To delete all
the keys in a bucket, you’ll need to delete them all individually."