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