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<FONT color="green">001</FONT>    /**<a name="line.1"></a>
<FONT color="green">002</FONT>     * Licensed to the Apache Software Foundation (ASF) under one<a name="line.2"></a>
<FONT color="green">003</FONT>     * or more contributor license agreements.  See the NOTICE file<a name="line.3"></a>
<FONT color="green">004</FONT>     * distributed with this work for additional information<a name="line.4"></a>
<FONT color="green">005</FONT>     * regarding copyright ownership.  The ASF licenses this file<a name="line.5"></a>
<FONT color="green">006</FONT>     * to you under the Apache License, Version 2.0 (the<a name="line.6"></a>
<FONT color="green">007</FONT>     * "License"); you may not use this file except in compliance<a name="line.7"></a>
<FONT color="green">008</FONT>     * with the License.  You may obtain a copy of the License at<a name="line.8"></a>
<FONT color="green">009</FONT>     *<a name="line.9"></a>
<FONT color="green">010</FONT>     *     http://www.apache.org/licenses/LICENSE-2.0<a name="line.10"></a>
<FONT color="green">011</FONT>     *<a name="line.11"></a>
<FONT color="green">012</FONT>     * Unless required by applicable law or agreed to in writing, software<a name="line.12"></a>
<FONT color="green">013</FONT>     * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.13"></a>
<FONT color="green">014</FONT>     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.14"></a>
<FONT color="green">015</FONT>     * See the License for the specific language governing permissions and<a name="line.15"></a>
<FONT color="green">016</FONT>     * limitations under the License.<a name="line.16"></a>
<FONT color="green">017</FONT>     */<a name="line.17"></a>
<FONT color="green">018</FONT>    package org.apache.hadoop.mapreduce.lib.join;<a name="line.18"></a>
<FONT color="green">019</FONT>    <a name="line.19"></a>
<FONT color="green">020</FONT>    import java.io.IOException;<a name="line.20"></a>
<FONT color="green">021</FONT>    <a name="line.21"></a>
<FONT color="green">022</FONT>    import org.apache.hadoop.classification.InterfaceAudience;<a name="line.22"></a>
<FONT color="green">023</FONT>    import org.apache.hadoop.classification.InterfaceStability;<a name="line.23"></a>
<FONT color="green">024</FONT>    import org.apache.hadoop.io.Writable;<a name="line.24"></a>
<FONT color="green">025</FONT>    <a name="line.25"></a>
<FONT color="green">026</FONT>    /**<a name="line.26"></a>
<FONT color="green">027</FONT>     * This defines an interface to a stateful Iterator that can replay elements<a name="line.27"></a>
<FONT color="green">028</FONT>     * added to it directly.<a name="line.28"></a>
<FONT color="green">029</FONT>     * Note that this does not extend {@link java.util.Iterator}.<a name="line.29"></a>
<FONT color="green">030</FONT>     */<a name="line.30"></a>
<FONT color="green">031</FONT>    @InterfaceAudience.Public<a name="line.31"></a>
<FONT color="green">032</FONT>    @InterfaceStability.Stable<a name="line.32"></a>
<FONT color="green">033</FONT>    public interface ResetableIterator&lt;T extends Writable&gt; {<a name="line.33"></a>
<FONT color="green">034</FONT>    <a name="line.34"></a>
<FONT color="green">035</FONT>      public static class EMPTY&lt;U extends Writable&gt;<a name="line.35"></a>
<FONT color="green">036</FONT>        implements ResetableIterator&lt;U&gt; {<a name="line.36"></a>
<FONT color="green">037</FONT>        public boolean hasNext() { return false; }<a name="line.37"></a>
<FONT color="green">038</FONT>        public void reset() { }<a name="line.38"></a>
<FONT color="green">039</FONT>        public void close() throws IOException { }<a name="line.39"></a>
<FONT color="green">040</FONT>        public void clear() { }<a name="line.40"></a>
<FONT color="green">041</FONT>        public boolean next(U val) throws IOException {<a name="line.41"></a>
<FONT color="green">042</FONT>          return false;<a name="line.42"></a>
<FONT color="green">043</FONT>        }<a name="line.43"></a>
<FONT color="green">044</FONT>        public boolean replay(U val) throws IOException {<a name="line.44"></a>
<FONT color="green">045</FONT>          return false;<a name="line.45"></a>
<FONT color="green">046</FONT>        }<a name="line.46"></a>
<FONT color="green">047</FONT>        public void add(U item) throws IOException {<a name="line.47"></a>
<FONT color="green">048</FONT>          throw new UnsupportedOperationException();<a name="line.48"></a>
<FONT color="green">049</FONT>        }<a name="line.49"></a>
<FONT color="green">050</FONT>      }<a name="line.50"></a>
<FONT color="green">051</FONT>    <a name="line.51"></a>
<FONT color="green">052</FONT>      /**<a name="line.52"></a>
<FONT color="green">053</FONT>       * True if a call to next may return a value. This is permitted false<a name="line.53"></a>
<FONT color="green">054</FONT>       * positives, but not false negatives.<a name="line.54"></a>
<FONT color="green">055</FONT>       */<a name="line.55"></a>
<FONT color="green">056</FONT>      public boolean hasNext();<a name="line.56"></a>
<FONT color="green">057</FONT>    <a name="line.57"></a>
<FONT color="green">058</FONT>      /**<a name="line.58"></a>
<FONT color="green">059</FONT>       * Assign next value to actual.<a name="line.59"></a>
<FONT color="green">060</FONT>       * It is required that elements added to a ResetableIterator be returned in<a name="line.60"></a>
<FONT color="green">061</FONT>       * the same order after a call to {@link #reset} (FIFO).<a name="line.61"></a>
<FONT color="green">062</FONT>       *<a name="line.62"></a>
<FONT color="green">063</FONT>       * Note that a call to this may fail for nested joins (i.e. more elements<a name="line.63"></a>
<FONT color="green">064</FONT>       * available, but none satisfying the constraints of the join)<a name="line.64"></a>
<FONT color="green">065</FONT>       */<a name="line.65"></a>
<FONT color="green">066</FONT>      public boolean next(T val) throws IOException;<a name="line.66"></a>
<FONT color="green">067</FONT>    <a name="line.67"></a>
<FONT color="green">068</FONT>      /**<a name="line.68"></a>
<FONT color="green">069</FONT>       * Assign last value returned to actual.<a name="line.69"></a>
<FONT color="green">070</FONT>       */<a name="line.70"></a>
<FONT color="green">071</FONT>      public boolean replay(T val) throws IOException;<a name="line.71"></a>
<FONT color="green">072</FONT>    <a name="line.72"></a>
<FONT color="green">073</FONT>      /**<a name="line.73"></a>
<FONT color="green">074</FONT>       * Set iterator to return to the start of its range. Must be called after<a name="line.74"></a>
<FONT color="green">075</FONT>       * calling {@link #add} to avoid a ConcurrentModificationException.<a name="line.75"></a>
<FONT color="green">076</FONT>       */<a name="line.76"></a>
<FONT color="green">077</FONT>      public void reset();<a name="line.77"></a>
<FONT color="green">078</FONT>    <a name="line.78"></a>
<FONT color="green">079</FONT>      /**<a name="line.79"></a>
<FONT color="green">080</FONT>       * Add an element to the collection of elements to iterate over.<a name="line.80"></a>
<FONT color="green">081</FONT>       */<a name="line.81"></a>
<FONT color="green">082</FONT>      public void add(T item) throws IOException;<a name="line.82"></a>
<FONT color="green">083</FONT>    <a name="line.83"></a>
<FONT color="green">084</FONT>      /**<a name="line.84"></a>
<FONT color="green">085</FONT>       * Close datasources and release resources. Calling methods on the iterator<a name="line.85"></a>
<FONT color="green">086</FONT>       * after calling close has undefined behavior.<a name="line.86"></a>
<FONT color="green">087</FONT>       */<a name="line.87"></a>
<FONT color="green">088</FONT>      // XXX is this necessary?<a name="line.88"></a>
<FONT color="green">089</FONT>      public void close() throws IOException;<a name="line.89"></a>
<FONT color="green">090</FONT>    <a name="line.90"></a>
<FONT color="green">091</FONT>      /**<a name="line.91"></a>
<FONT color="green">092</FONT>       * Close datasources, but do not release internal resources. Calling this<a name="line.92"></a>
<FONT color="green">093</FONT>       * method should permit the object to be reused with a different datasource.<a name="line.93"></a>
<FONT color="green">094</FONT>       */<a name="line.94"></a>
<FONT color="green">095</FONT>      public void clear();<a name="line.95"></a>
<FONT color="green">096</FONT>    <a name="line.96"></a>
<FONT color="green">097</FONT>    }<a name="line.97"></a>




























































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