001/*
002 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved.
003 *
004 * Project and contact information: http://www.cascading.org/
005 *
006 * This file is part of the Cascading project.
007 *
008 * Licensed under the Apache License, Version 2.0 (the "License");
009 * you may not use this file except in compliance with the License.
010 * You may obtain a copy of the License at
011 *
012 *     http://www.apache.org/licenses/LICENSE-2.0
013 *
014 * Unless required by applicable law or agreed to in writing, software
015 * distributed under the License is distributed on an "AS IS" BASIS,
016 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
017 * See the License for the specific language governing permissions and
018 * limitations under the License.
019 */
020
021package cascading.operation.aggregator;
022
023import java.beans.ConstructorProperties;
024
025import cascading.operation.Aggregator;
026import cascading.tuple.Fields;
027import cascading.tuple.Tuple;
028import cascading.tuple.TupleEntry;
029
030/**
031 * Class Last is an {@link Aggregator} that returns the last {@link Tuple} encountered.
032 * <p/>
033 * By default, it returns the last Tuple of {@link Fields#ARGS} found.
034 */
035public class Last extends ExtentBase
036  {
037  /** Selects and returns the last argument Tuple encountered. */
038  public Last()
039    {
040    super( Fields.ARGS );
041    }
042
043  /**
044   * Selects and returns the last argument Tuple encountered.
045   *
046   * @param fieldDeclaration of type Fields
047   */
048  @ConstructorProperties({"fieldDeclaration"})
049  public Last( Fields fieldDeclaration )
050    {
051    super( fieldDeclaration.size(), fieldDeclaration );
052    }
053
054  /**
055   * Selects and returns the last argument Tuple encountered, unless the Tuple
056   * is a member of the set ignoreTuples.
057   *
058   * @param fieldDeclaration of type Fields
059   * @param ignoreTuples     of type Tuple...
060   */
061  @ConstructorProperties({"fieldDeclaration", "ignoreTuples"})
062  public Last( Fields fieldDeclaration, Tuple... ignoreTuples )
063    {
064    super( fieldDeclaration, ignoreTuples );
065    }
066
067  protected void performOperation( Tuple[] context, TupleEntry entry )
068    {
069    context[ 0 ] = entry.getTupleCopy();
070    }
071  }