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    1   package org.apache.lucene.search.highlight;
    2   
    3   /**
    4    * Licensed to the Apache Software Foundation (ASF) under one or more
    5    * contributor license agreements.  See the NOTICE file distributed with
    6    * this work for additional information regarding copyright ownership.
    7    * The ASF licenses this file to You under the Apache License, Version 2.0
    8    * (the "License"); you may not use this file except in compliance with
    9    * the License.  You may obtain a copy of the License at
   10    *
   11    *     http://www.apache.org/licenses/LICENSE-2.0
   12    *
   13    * Unless required by applicable law or agreed to in writing, software
   14    * distributed under the License is distributed on an "AS IS" BASIS,
   15    * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   16    * See the License for the specific language governing permissions and
   17    * limitations under the License.
   18    */
   19   
   20   import java.io.IOException;
   21   
   22   import org.apache.lucene.analysis.TokenStream;
   23   
   24   /**
   25    * A Scorer is responsible for scoring a stream of tokens. These token scores
   26    * can then be used to compute {@link TextFragment} scores.
   27    */
   28   public interface Scorer {
   29   
   30     /**
   31      * Called to init the Scorer with a {@link TokenStream}. You can grab references to
   32      * the attributes you are interested in here and access them from {@link #getTokenScore()}.
   33      * 
   34      * @param tokenStream the {@link TokenStream} that will be scored.
   35      * @return either a {@link TokenStream} that the Highlighter should continue using (eg
   36      *         if you read the tokenSream in this method) or null to continue
   37      *         using the same {@link TokenStream} that was passed in.
   38      * @throws IOException
   39      */
   40     public TokenStream init(TokenStream tokenStream) throws IOException;
   41   
   42     /**
   43      * Called when a new fragment is started for consideration.
   44      * 
   45      * @param newFragment the fragment that will be scored next
   46      */
   47     public void startFragment(TextFragment newFragment);
   48   
   49     /**
   50      * Called for each token in the current fragment. The {@link Highlighter} will
   51      * increment the {@link TokenStream} passed to init on every call.
   52      * 
   53      * @return a score which is passed to the {@link Highlighter} class to influence the
   54      *         mark-up of the text (this return value is NOT used to score the
   55      *         fragment)
   56      */
   57     public float getTokenScore();
   58   
   59     /**
   60      * Called when the {@link Highlighter} has no more tokens for the current fragment -
   61      * the Scorer returns the weighting it has derived for the most recent
   62      * fragment, typically based on the results of {@link #getTokenScore()}.
   63      * 
   64      */
   65     public float getFragmentScore();
   66   
   67   }

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