@Override
  public double divideForAvg(Double d1, Long l2) {
    return (l2 == null || d1 == null) ? Double.NaN : (d1.doubleValue() / l2.doubleValue());
  }
a concrete column interpreter implementation. The cell value is a Double value and its promoted
data type is also a Double value. For computing aggregation function, this class is used to find
the datatype of the cell value. Client is supposed to instantiate it and passed along as a
parameter. See TestDoubleColumnInterpreter methods for its sample usage. Its methods handle null
arguments gracefully.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/coprocessor/DoubleColumnInterpreter.java