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 package org.apache.hadoop.mapreduce.lib.join;
019
020 import java.io.IOException;
021 import java.util.ArrayList;
022 import java.util.Iterator;
023
024 import org.apache.hadoop.classification.InterfaceAudience;
025 import org.apache.hadoop.classification.InterfaceStability;
026 import org.apache.hadoop.conf.Configuration;
027 import org.apache.hadoop.io.Writable;
028 import org.apache.hadoop.io.WritableUtils;
029 import org.apache.hadoop.util.ReflectionUtils;
030
031 /**
032 * This class provides an implementation of ResetableIterator. The
033 * implementation uses an {@link java.util.ArrayList} to store elements
034 * added to it, replaying them as requested.
035 * Prefer {@link StreamBackedIterator}.
036 */
037 @InterfaceAudience.Public
038 @InterfaceStability.Stable
039 public class ArrayListBackedIterator<X extends Writable>
040 implements ResetableIterator<X> {
041
042 private Iterator<X> iter;
043 private ArrayList<X> data;
044 private X hold = null;
045 private Configuration conf = new Configuration();
046
047 public ArrayListBackedIterator() {
048 this(new ArrayList<X>());
049 }
050
051 public ArrayListBackedIterator(ArrayList<X> data) {
052 this.data = data;
053 this.iter = this.data.iterator();
054 }
055
056 public boolean hasNext() {
057 return iter.hasNext();
058 }
059
060 public boolean next(X val) throws IOException {
061 if (iter.hasNext()) {
062 ReflectionUtils.copy(conf, iter.next(), val);
063 if (null == hold) {
064 hold = WritableUtils.clone(val, null);
065 } else {
066 ReflectionUtils.copy(conf, val, hold);
067 }
068 return true;
069 }
070 return false;
071 }
072
073 public boolean replay(X val) throws IOException {
074 ReflectionUtils.copy(conf, hold, val);
075 return true;
076 }
077
078 public void reset() {
079 iter = data.iterator();
080 }
081
082 public void add(X item) throws IOException {
083 data.add(WritableUtils.clone(item, null));
084 }
085
086 public void close() throws IOException {
087 iter = null;
088 data = null;
089 }
090
091 public void clear() {
092 data.clear();
093 reset();
094 }
095 }