cascading.operation.aggregator
Class First

java.lang.Object
  cascading.operation.BaseOperation<Tuple[]>
      cascading.operation.aggregator.ExtentBase
          cascading.operation.aggregator.First

All Implemented Interfaces:

Aggregator<Tuple[]>, Operation<Tuple[]>, Serializable

public class First
extends ExtentBase

Class First is an Aggregator that returns the first Tuple encountered.

By default, it returns the first Tuple of Fields.ARGS found.

See Also:

Serialized Form

Field Summary

Fields inherited from class cascading.operation.BaseOperation

fieldDeclaration, numArgs, trace

Fields inherited from interface cascading.operation.Operation

ANY

Constructor Summary

First()
Selects and returns the first argument Tuple encountered.

First(Fields fieldDeclaration)
Selects and returns the first argument Tuple encountered.

First(Fields fieldDeclaration, Tuple... ignoreTuples)
Selects and returns the first argument Tuple encountered, unless the Tuple is a member of the set ignoreTuples.

Method Summary

protected void

performOperation(Tuple[] context, TupleEntry entry)

Methods inherited from class cascading.operation.aggregator.ExtentBase

aggregate, complete, getResult, start

Methods inherited from class cascading.operation.BaseOperation

cleanup, getFieldDeclaration, getNumArgs, getTrace, prepare, printOperationInternal, toString, toStringInternal

Methods inherited from class java.lang.Object

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

Methods inherited from interface cascading.operation.Operation

cleanup, getFieldDeclaration, getNumArgs, prepare

Constructor Detail

First

public First()

Selects and returns the first argument Tuple encountered.

First

public First(Fields fieldDeclaration)

Selects and returns the first argument Tuple encountered.

Parameters:

fieldDeclaration - of type Fields

First

public First(Fields fieldDeclaration,
             Tuple... ignoreTuples)

Selects and returns the first argument Tuple encountered, unless the Tuple is a member of the set ignoreTuples.

Parameters:

fieldDeclaration - of type Fields

ignoreTuples - of type Tuple...

Method Detail

performOperation

protected void performOperation(Tuple[] context,
                                TupleEntry entry)

Specified by:

performOperation in class ExtentBase