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com.tangosol.util.aggregator
Class AbstractComparableAggregator

java.lang.Object
com.tangosol.util.Base
com.tangosol.util.BitHelper
com.tangosol.util.ExternalizableHelper
com.tangosol.util.aggregator.AbstractAggregator
com.tangosol.util.aggregator.AbstractComparableAggregator

All Implemented Interfaces:

ExternalizableLite, PortableObject, InvocableMap.EntryAggregator, InvocableMap.ParallelAwareAggregator, Serializable

Direct Known Subclasses:

ComparableMax, ComparableMin

public abstract class AbstractComparableAggregator

extends AbstractAggregator

Abstract aggregator that processes values extracted from a set of entries in a Map, with knowledge of how to compare those values. There are two way to use the AbstractComparableAggregator:

• All the extracted objects must implement Comparable, or
• The AbstractComparableAggregator has to be provided with a Comparator object.

If the set of entries passed to AbstractAggregator.aggregate(java.util.Set) is empty, a null result is returned.

Since:

Coherence 3.2

Author:

gg 2006.02.13

Field Summary

protected Comparator	m_comparator The comparator to use for comparing extracted values.
protected int	m_count The count of processed entries.
protected Object	m_oResult The running result value.

Fields inherited from class com.tangosol.util.aggregator.AbstractAggregator

m_fParallel

Constructor Summary

AbstractComparableAggregator()
Default constructor (necessary for the ExternalizableLite interface).

AbstractComparableAggregator(String sMethod)
Construct an AbstractComparableAggregator object.

AbstractComparableAggregator(ValueExtractor extractor)
Construct an AbstractComparableAggregator object.

AbstractComparableAggregator(ValueExtractor extractor, Comparator comparator)
Construct an AbstractComparableAggregator object.

Method Summary

protected Object	finalizeResult(boolean fFinal) Obtain the result of the aggregation.
protected void	init(boolean fFinal) Initialize the aggregation result.
void	readExternal(DataInput in) Restore the contents of this object by loading the object's state from the passed DataInput object.
void	readExternal(PofReader in) Restore the contents of a user type instance by reading its state using the specified PofReader object.
void	writeExternal(DataOutput out) Save the contents of this object by storing the object's state into the passed DataOutput object.
void	writeExternal(PofWriter out) Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

Methods inherited from class com.tangosol.util.aggregator.AbstractAggregator

aggregate, aggregateResults, equals, getParallelAggregator, getValueExtractor, hashCode, process, processEntry, toString

Methods inherited from class com.tangosol.util.BitHelper

countBits, countBits, countBits, indexOfLSB, indexOfLSB, indexOfLSB, indexOfMSB, indexOfMSB, indexOfMSB, rotateLeft, rotateLeft, rotateLeft, rotateRight, rotateRight, rotateRight, toBitString, toBitString, toBitString

Field Detail

m_count

protected transient int m_count

The count of processed entries.

m_oResult

protected transient Object m_oResult

The running result value.

m_comparator

protected Comparator m_comparator

The comparator to use for comparing extracted values.

Constructor Detail

AbstractComparableAggregator

public AbstractComparableAggregator()

Default constructor (necessary for the ExternalizableLite interface).

AbstractComparableAggregator

public AbstractComparableAggregator(ValueExtractor extractor)

Construct an AbstractComparableAggregator object.

Parameters:

extractor - the extractor that provides a value in the form of any object that implements the Comparable interface

AbstractComparableAggregator

public AbstractComparableAggregator(ValueExtractor extractor,
                                    Comparator comparator)

Construct an AbstractComparableAggregator object.

Parameters:

extractor - the extractor that provides an object to be compared

comparator - the comparator used to compare the extracted object

AbstractComparableAggregator

public AbstractComparableAggregator(String sMethod)

Construct an AbstractComparableAggregator object.

Parameters:

sMethod - the name of the method that returns a value in the form of any object that implements the Comparable interface

Method Detail

init

protected void init(boolean fFinal)

Initialize the aggregation result.

Specified by:

init in class AbstractAggregator

Parameters:

fFinal - true is passed if the aggregation process that is being initialized must produce a final aggregation result; this will only be false if a parallel approach is being used and the initial (partial) aggregation process is being initialized

finalizeResult

protected Object finalizeResult(boolean fFinal)

Obtain the result of the aggregation. <p/> If the fFinal parameter is true, the returned object must be the final result of the aggregation; otherwise, the returned object will be treated as a partial result that should be incorporated into the final result.

Specified by:

finalizeResult in class AbstractAggregator

Parameters:

fFinal - true to indicate that the final result of the aggregation process should be returned; this will only be false if a parallel approach is being used

Returns:

the result of the aggregation process

readExternal

public void readExternal(DataInput in)
                  throws IOException

Restore the contents of this object by loading the object's state from the passed DataInput object.

Specified by:

readExternal in interface ExternalizableLite

Overrides:

readExternal in class AbstractAggregator

Parameters:

in - the DataInput stream to read data from in order to restore the state of this object

Throws:

IOException - if an I/O exception occurs

NotActiveException - if the object is not in its initial state, and therefore cannot be deserialized into

writeExternal

public void writeExternal(DataOutput out)
                   throws IOException

Save the contents of this object by storing the object's state into the passed DataOutput object.

Specified by:

writeExternal in interface ExternalizableLite

Overrides:

writeExternal in class AbstractAggregator

Parameters:

out - the DataOutput stream to write the state of this object to

Throws:

IOException - if an I/O exception occurs

readExternal

public void readExternal(PofReader in)
                  throws IOException

Restore the contents of a user type instance by reading its state using the specified PofReader object.

Specified by:

readExternal in interface PortableObject

Overrides:

readExternal in class AbstractAggregator

Parameters:

in - the PofReader from which to read the object's state

Throws:

IOException - if an I/O error occurs

writeExternal

public void writeExternal(PofWriter out)
                   throws IOException

Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

Specified by:

writeExternal in interface PortableObject

Overrides:

writeExternal in class AbstractAggregator

Parameters:

out - the PofWriter to which to write the object's state

Throws:

IOException - if an I/O error occurs

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