001/*
002 * Copyright (c) 2016-2017 Chris K Wensel <chris@wensel.net>. All Rights Reserved.
003 * Copyright (c) 2007-2017 Xplenty, Inc. All Rights Reserved.
004 *
005 * Project and contact information: http://www.cascading.org/
006 *
007 * This file is part of the Cascading project.
008 *
009 * Licensed under the Apache License, Version 2.0 (the "License");
010 * you may not use this file except in compliance with the License.
011 * You may obtain a copy of the License at
012 *
013 *     http://www.apache.org/licenses/LICENSE-2.0
014 *
015 * Unless required by applicable law or agreed to in writing, software
016 * distributed under the License is distributed on an "AS IS" BASIS,
017 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
018 * See the License for the specific language governing permissions and
019 * limitations under the License.
020 */
021
022package cascading.operation.aggregator;
023
024import java.beans.ConstructorProperties;
025
026import cascading.operation.Aggregator;
027import cascading.tuple.Fields;
028import cascading.tuple.Tuple;
029import cascading.tuple.TupleEntry;
030
031/**
032 * Class Last is an {@link Aggregator} that returns the last {@link Tuple} encountered.
033 * <p>
034 * By default, it returns the last Tuple of {@link Fields#ARGS} found.
035 */
036public class Last extends ExtentBase
037  {
038  /** Selects and returns the last argument Tuple encountered. */
039  public Last()
040    {
041    super( Fields.ARGS );
042    }
043
044  /**
045   * Selects and returns the last argument Tuple encountered.
046   *
047   * @param fieldDeclaration of type Fields
048   */
049  @ConstructorProperties({"fieldDeclaration"})
050  public Last( Fields fieldDeclaration )
051    {
052    super( fieldDeclaration.size(), fieldDeclaration );
053    }
054
055  /**
056   * Selects and returns the last argument Tuple encountered, unless the Tuple
057   * is a member of the set ignoreTuples.
058   *
059   * @param fieldDeclaration of type Fields
060   * @param ignoreTuples     of type Tuple...
061   */
062  @ConstructorProperties({"fieldDeclaration", "ignoreTuples"})
063  public Last( Fields fieldDeclaration, Tuple... ignoreTuples )
064    {
065    super( fieldDeclaration, ignoreTuples );
066    }
067
068  protected void performOperation( Tuple[] context, TupleEntry entry )
069    {
070    context[ 0 ] = entry.getTupleCopy();
071    }
072  }