public void init() {
      if (state.counts != null) {
        // We reuse the same hashmap to reduce new object allocation.
        // This means counts can be empty when there is no input data.
        state.counts.clear();
      }
    }
The evaluator for percentile computation based on long for an array of percentiles.
ql/src/java/org/apache/hadoop/hive/ql/udf/UDAFPercentile.java