Package org.apache.storm.streams.operations.aggregators

Class Count<T>

java.lang.Object

org.apache.storm.streams.operations.aggregators.Count<T>

Type Parameters:

T - the value type

All Implemented Interfaces:

Serializable, CombinerAggregator<T,Long,Long>, Operation

public class Count<T>
extends Object
implements CombinerAggregator<T,Long,Long>

Computes the count of values.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor	Description
Count()

Method Summary

Modifier and Type	Method	Description
Long	apply(Long accum, T value)	Updates the accumulator by applying the current accumulator with the value.
Long	init()	The initial value of the accumulator to start with.
Long	merge(Long accum1, Long accum2)	Merges two accumulators and returns the merged accumulator.
Long	result(Long accum)	Produces a result value out of the accumulator.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Count

public Count()

Method Detail

init

public Long init()

Description copied from interface: CombinerAggregator

The initial value of the accumulator to start with.

Specified by:

init in interface CombinerAggregator<T,Long,Long>

Returns:

the initial value of the accumulator

apply

public Long apply(Long accum,
                  T value)

Description copied from interface: CombinerAggregator

Updates the accumulator by applying the current accumulator with the value.

Specified by:

apply in interface CombinerAggregator<T,Long,Long>

Parameters:

accum - the current accumulator

value - the value

Returns:

the updated accumulator

merge

public Long merge(Long accum1,
                  Long accum2)

Description copied from interface: CombinerAggregator

Merges two accumulators and returns the merged accumulator.

Specified by:

merge in interface CombinerAggregator<T,Long,Long>

Parameters:

accum1 - the first accumulator

accum2 - the second accumulator

Returns:

the merged accumulator

result

public Long result(Long accum)

Description copied from interface: CombinerAggregator

Produces a result value out of the accumulator.

Specified by:

result in interface CombinerAggregator<T,Long,Long>

Parameters:

accum - the accumulator

Returns:

the result