public String terminate() {
      Collections.sort(data);
      StringBuilder sb = new StringBuilder();
      for (int i = 0; i < data.size(); i++) {
        sb.append(data.get(i));
      }
      return sb.toString();
    }
Terminates the aggregation and return the final result.
contrib/src/java/org/apache/hadoop/hive/contrib/udaf/example/UDAFExampleGroupConcat.java