package org.apache.lucene.search;/** * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements.  See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License.  You may obtain a copy of the License at * *     http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */import java.io.IOException;/** * Expert: Common scoring functionality for different types of queries. * * <p> * A <code>Scorer</code> either iterates over documents matching a * query in increasing order of doc Id, or provides an explanation of * the score for a query for a given document. * </p> * <p> * Document scores are computed using a given <code>Similarity</code> * implementation. * </p> * @see BooleanQuery#setAllowDocsOutOfOrder */public abstract class Scorer extends DocIdSetIterator {  private Similarity similarity;  /** Constructs a Scorer.   * @param similarity The <code>Similarity</code> implementation used by this scorer.   */  protected Scorer(Similarity similarity) {    this.similarity = similarity;  }  /** Returns the Similarity implementation used by this scorer. */  public Similarity getSimilarity() {    return this.similarity;  }  /** Scores and collects all matching documents.   * @param hc The collector to which all matching documents are passed through   * {@link HitCollector#collect(int, float)}.   * <br>When this method is used the {@link #explain(int)} method should not be used.   */  public void score(HitCollector hc) throws IOException {    while (next()) {      hc.collect(doc(), score());    }  }  /** Expert: Collects matching documents in a range.  Hook for optimization.   * Note that {@link #next()} must be called once before this method is called   * for the first time.   * @param hc The collector to which all matching documents are passed through   * {@link HitCollector#collect(int, float)}.   * @param max Do not score documents past this.   * @return true if more matching documents may remain.   */  protected boolean score(HitCollector hc, int max) throws IOException {    while (doc() < max) {      hc.collect(doc(), score());      if (!next())        return false;    }    return true;  }  /** Returns the score of the current document matching the query.   * Initially invalid, until {@link #next()} or {@link #skipTo(int)}   * is called the first time.   */  public abstract float score() throws IOException;  /** Returns an explanation of the score for a document.   * <br>When this method is used, the {@link #next()}, {@link #skipTo(int)} and   * {@link #score(HitCollector)} methods should not be used.   * @param doc The document number for the explanation.   */  public abstract Explanation explain(int doc) throws IOException;}