code: public void clear() {
  		Mutator<K> mutator = HFactory.createMutator(this.keyspace, this.keySerializer, new BatchSizeHint(1, this.mutateInterval));
  
  		SliceCounterQuery<K, N> query = HFactory.createCounterSliceQuery(this.keyspace, this.keySerializer, this.nameSerializer).
  						setColumnFamily(this.cf).
  						setKey(this.rowKey);
  
  		SliceCounterIterator<K, N> iterator =
  						new SliceCounterIterator<K, N>(query, null, (N) null, false, this.count);
  
  		while(iterator.hasNext()) {
  			HCounterColumn<N> column = iterator.next();
  			mutator.incrementCounter(this.rowKey, this.cf, column.getName(), column.getValue() * -1);
  		}
  
  		mutator.execute();
  	}
docs: Clear the counter columns.