001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one
003     * or more contributor license agreements.  See the NOTICE file
004     * distributed with this work for additional information
005     * regarding copyright ownership.  The ASF licenses this file
006     * to you under the Apache License, Version 2.0 (the
007     * "License"); you may not use this file except in compliance
008     * with the License.  You may obtain a copy of the License at
009     *
010     *     http://www.apache.org/licenses/LICENSE-2.0
011     *
012     * Unless required by applicable law or agreed to in writing, software
013     * distributed under the License is distributed on an "AS IS" BASIS,
014     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015     * See the License for the specific language governing permissions and
016     * limitations under the License.
017     */
018    
019    package org.apache.hadoop.mapreduce;
020    
021    import java.io.IOException;
022    import java.util.Iterator;
023    
024    import org.apache.hadoop.classification.InterfaceAudience;
025    import org.apache.hadoop.classification.InterfaceStability;
026    
027    /**
028     * <code>MarkableIterator</code> is a wrapper iterator class that 
029     * implements the {@link MarkableIteratorInterface}.
030     * 
031     */
032    @InterfaceAudience.Public
033    @InterfaceStability.Evolving
034    public class MarkableIterator<VALUE> 
035      implements MarkableIteratorInterface<VALUE> {
036    
037      MarkableIteratorInterface<VALUE> baseIterator;
038    
039      /**
040       * Create a new iterator layered on the input iterator
041       * @param itr underlying iterator that implements MarkableIteratorInterface
042       */
043      public MarkableIterator(Iterator<VALUE> itr)  {
044        if (!(itr instanceof MarkableIteratorInterface)) {
045          throw new IllegalArgumentException("Input Iterator not markable");
046        }
047        baseIterator = (MarkableIteratorInterface<VALUE>) itr;
048      }
049    
050      @Override
051      public void mark() throws IOException {
052        baseIterator.mark();
053      }
054    
055      @Override
056      public void reset() throws IOException {
057        baseIterator.reset();
058      }
059    
060      @Override
061      public void clearMark() throws IOException {
062        baseIterator.clearMark();
063      }
064    
065      @Override
066      public boolean hasNext() { 
067        return baseIterator.hasNext();
068      }
069    
070      @Override
071      public VALUE next() {
072        return baseIterator.next();
073      }
074    
075      @Override
076      public void remove() {
077        throw new UnsupportedOperationException("Remove Not Implemented");
078      }
079    }