| package org.apache.lucene.search; |
| |
| /** |
| * Copyright 2004 The Apache Software Foundation |
| * |
| * Licensed 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: Implements scoring for a class of queries. */ |
| public abstract class Scorer { |
| private Similarity similarity; |
| |
| /** Constructs a Scorer. */ |
| protected Scorer(Similarity similarity) { |
| this.similarity = similarity; |
| } |
| |
| /** Returns the Similarity implementation used by this scorer. */ |
| public Similarity getSimilarity() { |
| return this.similarity; |
| } |
| |
| /** Scores all documents and passes them to a collector. */ |
| public void score(HitCollector hc) throws IOException { |
| while (next()) { |
| hc.collect(doc(), score()); |
| } |
| } |
| |
| /** Advance to the next document matching the query. Returns true iff there |
| * is another match. */ |
| public abstract boolean next() throws IOException; |
| |
| /** Returns the current document number. Initially invalid, until {@link |
| * #next()} is called the first time. */ |
| public abstract int doc(); |
| |
| /** Returns the score of the current document. Initially invalid, until |
| * {@link #next()} is called the first time. */ |
| public abstract float score() throws IOException; |
| |
| /** Skips to the first match beyond the current whose document number is |
| * greater than or equal to <i>target</i>. <p>Returns true iff there is such |
| * a match. <p>Behaves as if written: <pre> |
| * boolean skipTo(int target) { |
| * do { |
| * if (!next()) |
| * return false; |
| * } while (target > doc()); |
| * return true; |
| * } |
| * </pre> |
| * Most implementations are considerably more efficient than that. |
| */ |
| public abstract boolean skipTo(int target) throws IOException; |
| |
| /** Returns an explanation of the score for <code>doc</code>. */ |
| public abstract Explanation explain(int doc) throws IOException; |
| |
| } |