    001    /*
    002     * Copyright (c) 2007-2014 Concurrent, 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
    021    package cascading.tuple;
    022
    023    import java.io.Closeable;
    024    import java.io.IOException;
    025    import 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     */
    032    public class TupleEntryChainIterator extends TupleEntryIterator
    033      {
    034      /** Field iterator */
    035      Iterator<Tuple>[] iterators;
    036      int currentIterator = 0;
    037
    038      public TupleEntryChainIterator( Fields fields, Iterator<Tuple>... iterators )
    039        {
    040        super( fields );
    041        this.iterators = iterators;
    042        }
    043
    044      /**
    045       * Method hasNext returns true if there is a next TupleEntry
    046       *
    047       * @return boolean
    048       */
    049      public boolean hasNext()
    050        {
    051        if( iterators.length < currentIterator + 1 ) // past the end
    052          return false;
    053
    054        if( iterators[ currentIterator ].hasNext() )
    055          return true;
    056
    057        closeCurrent();
    058
    059        currentIterator++;
    060
    061        return iterators.length != currentIterator && hasNext();
    062        }
    063
    064      public void reset( Iterator<Tuple>... iterators )
    065        {
    066        this.currentIterator = 0;
    067        this.iterators = iterators;
    068        }
    069
    070      /**
    071       * Method next returns the next TupleEntry.
    072       *
    073       * @return TupleEntry
    074       */
    075      public TupleEntry next()
    076        {
    077        hasNext(); // force roll to next iterator
    078
    079        entry.setTuple( iterators[ currentIterator ].next() );
    080
    081        return entry;
    082        }
    083
    084      /** Method remove removes the current TupleEntry from the underlying collection. */
    085      public void remove()
    086        {
    087        iterators[ currentIterator ].remove();
    088        }
    089
    090      /** Method close closes all underlying resources. */
    091      public void close()
    092        {
    093        if( iterators.length != currentIterator )
    094          closeCurrent();
    095        }
    096
    097      protected void closeCurrent()
    098        {
    099        close( iterators[ currentIterator ] );
    100        }
    101
    102      private void close( Iterator iterator )
    103        {
    104        if( iterator instanceof Closeable )
    105          {
    106          try
    107            {
    108            ( (Closeable) iterator ).close();
    109            }
    110          catch( IOException exception )
    111            {
    112            // ignore
    113            }
    114          }
    115        }
    116      }