flink sql hop????????udaf????

[bigdata]

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    flink1.10.1 
sql??????hop??????udaf??merge??????????????????????????????????????????????????merge??????
org.apache.flink.table.planner.codegen.CodeGenException: No matching merge 
method found for AggregateFunction com.autoai.cns.udaf.PercentileUDAF'
def merge(accumulator: ListBuffer[Float], its: Iterable[ListBuffer[Float]]): 
Unit = {
  its.foreach(i => accumulator ++ i)
}