com.espertech.esper.epl.agg.aggregator
Class AggregatorNth

java.lang.Object
  com.espertech.esper.epl.agg.aggregator.AggregatorNth

All Implemented Interfaces:

AggregationMethod

public class AggregatorNth
extends java.lang.Object
implements AggregationMethod

Aggregator to return the Nth oldest element to enter, with N=1 the most recent value is returned. If N is larger than the enter minus leave size, null is returned. A maximum N historical values are stored, so it can be safely used to compare recent values in large views without incurring excessive overhead.

Field Summary

protected java.lang.Object[]	circularBuffer
protected int	currentBufferElementPointer
protected long	numDataPoints
protected java.lang.Class	returnType
protected int	sizeBuf

Constructor Summary

AggregatorNth(java.lang.Class returnType, int sizeBuf)
Ctor.

Method Summary

void	clear() Clear out the collection.
void	enter(java.lang.Object value) Apply the value as entering aggregation (entering window).
java.lang.Object	getValue() Returns the current value held.
java.lang.Class	getValueType() Returns the type of the current value.
void	leave(java.lang.Object value) Apply the value as leaving aggregation (leaving window).

Methods inherited from class java.lang.Object

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

Field Detail

returnType

protected final java.lang.Class returnType

sizeBuf

protected final int sizeBuf

circularBuffer

protected java.lang.Object[] circularBuffer

currentBufferElementPointer

protected int currentBufferElementPointer

numDataPoints

protected long numDataPoints

Constructor Detail

AggregatorNth

public AggregatorNth(java.lang.Class returnType,
                     int sizeBuf)

Ctor.

Parameters:

returnType - return type

sizeBuf - size

Method Detail

enter

public void enter(java.lang.Object value)

Description copied from interface: AggregationMethod

Apply the value as entering aggregation (entering window).

The value can be null since 'null' values may be counted as unique separate values.

Specified by:

enter in interface AggregationMethod

Parameters:

value - to add to aggregate

leave

public void leave(java.lang.Object value)

Description copied from interface: AggregationMethod

Apply the value as leaving aggregation (leaving window).

The value can be null since 'null' values may be counted as unique separate values.

Specified by:

leave in interface AggregationMethod

Parameters:

value - to remove from aggregate

getValueType

public java.lang.Class getValueType()

Description copied from interface: AggregationMethod

Returns the type of the current value.

Specified by:

getValueType in interface AggregationMethod

Returns:

type of values held

getValue

public java.lang.Object getValue()

Description copied from interface: AggregationMethod

Returns the current value held.

Specified by:

getValue in interface AggregationMethod

Returns:

current value

clear

public void clear()

Description copied from interface: AggregationMethod

Clear out the collection.

Specified by:

clear in interface AggregationMethod