code: public void insertMulti(String columnName, Map<String, String> keyValues) {
      Mutator<String> m = createMutator(keyspace, serializer);
      for (Map.Entry<String, String> keyValue: keyValues.entrySet()) {
        m.addInsertion(keyValue.getKey(), columnFamilyName,
            createColumn(columnName, keyValue.getValue(), keyspace.createClock(), serializer, serializer));
      }
      m.execute();
    }
docs: Insert multiple values for a given columnName