    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.tuple;
    022
    023import java.io.Closeable;
    024import java.io.IOException;
    025import java.util.Iterator;
    026
    027/**
    028 * TupleEntryChainIterator chains the given Iterators into a single Iterator.
    029 * <p/>
    030 * As one iterator is completed, it will be closed and a new one will start.
    031 */
    032public class TupleEntryChainIterator extends TupleEntryIterator
    033  {
    034  /** Field iterator */
    035  Iterator<Tuple>[] iterators;
    036  int currentIterator = 0;
    037
    038  public TupleEntryChainIterator( Fields fields )
    039    {
    040    super( fields );
    041    this.iterators = new Iterator[ 1 ];
    042    }
    043
    044  public TupleEntryChainIterator( Fields fields, Iterator<Tuple> iterator )
    045    {
    046    this( fields );
    047    this.iterators[ 0 ] = iterator;
    048    }
    049
    050  public TupleEntryChainIterator( Fields fields, Iterator<Tuple>[] iterators )
    051    {
    052    super( fields );
    053    this.iterators = iterators;
    054    }
    055
    056  /**
    057   * Method hasNext returns true if there is a next TupleEntry
    058   *
    059   * @return boolean
    060   */
    061  public boolean hasNext()
    062    {
    063    if( iterators.length < currentIterator + 1 ) // past the end
    064      return false;
    065
    066    if( iterators[ currentIterator ].hasNext() )
    067      return true;
    068
    069    closeCurrent();
    070
    071    currentIterator++;
    072
    073    return iterators.length != currentIterator && hasNext();
    074    }
    075
    076  public void reset( Iterator<Tuple> iterator )
    077    {
    078    this.currentIterator = 0;
    079    this.iterators[ 0 ] = iterator;
    080    }
    081
    082  public void reset( Iterator<Tuple>[] iterators )
    083    {
    084    this.currentIterator = 0;
    085    this.iterators = iterators;
    086    }
    087
    088  /**
    089   * Method next returns the next TupleEntry.
    090   *
    091   * @return TupleEntry
    092   */
    093  public TupleEntry next()
    094    {
    095    hasNext(); // force roll to next iterator
    096
    097    entry.setTuple( iterators[ currentIterator ].next() );
    098
    099    return entry;
    100    }
    101
    102  /** Method remove removes the current TupleEntry from the underlying collection. */
    103  public void remove()
    104    {
    105    iterators[ currentIterator ].remove();
    106    }
    107
    108  /** Method close closes all underlying resources. */
    109  public void close()
    110    {
    111    if( iterators.length != currentIterator )
    112      closeCurrent();
    113    }
    114
    115  protected void closeCurrent()
    116    {
    117    close( iterators[ currentIterator ] );
    118    }
    119
    120  private void close( Iterator iterator )
    121    {
    122    if( iterator instanceof Closeable )
    123      {
    124      try
    125        {
    126        ( (Closeable) iterator ).close();
    127        }
    128      catch( IOException exception )
    129        {
    130        // ignore
    131        }
    132      }
    133    }
    134  }