# Package cascading.operation.aggregator

- Class Summary
  Class | Description
  --- | ---
  Average | Class Average is an `Aggregator` that returns the average of all numeric values in the current group.
  Average.Context | Class Context is used to hold intermediate values.
  Count | Class Count is an `Aggregator` that calculates the number of items in the current group.
  ExtentBase | Class ExtentBase is the base class for First and Last.
  ExtremaValueBase | Class ExtremaValueBase is the base class for MaxValue and MinValue where the values are expected to by `Comparable` types and the `Comparable.compareTo(Object)` result is use for max/min comparison.
  ExtremaValueBase.Context |
  First | Class First is an `Aggregator` that returns the first `Tuple` encountered in a grouping.
  Last | Class Last is an `Aggregator` that returns the last `Tuple` encountered.
  MaxValue | Class MaxValue is an `Aggregator` that returns the maximum value encountered in the current group.
  MinValue | Class Min is an `Aggregator` that returns the minimum value encountered in the current group.
  Sum | Class Sum is an `Aggregator` that returns the sum of all numeric values in the current group.

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