From 312400842fec93eaea07cb75ce6a11a21461300d Mon Sep 17 00:00:00 2001 From: Michael McCandless Date: Mon, 27 Jul 2009 10:02:34 +0000 Subject: [PATCH] LUCENE-1754: add EmptyDocIdSetIterator git-svn-id: https://svn.apache.org/repos/asf/lucene/java/trunk@798091 13f79535-47bb-0310-9956-ffa450edef68 --- .../lucene/search/EmptyDocIdSetIterator.java | 42 +++++++++++++++++++ 1 file changed, 42 insertions(+) create mode 100644 src/java/org/apache/lucene/search/EmptyDocIdSetIterator.java diff --git a/src/java/org/apache/lucene/search/EmptyDocIdSetIterator.java b/src/java/org/apache/lucene/search/EmptyDocIdSetIterator.java new file mode 100644 index 00000000000..5bd15f0228a --- /dev/null +++ b/src/java/org/apache/lucene/search/EmptyDocIdSetIterator.java @@ -0,0 +1,42 @@ +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; + +/** + * An empty implementation for {@link DocIdSetIterator}. This can be used by + * classes which receive a null {@link DocIdSet} from + * {@link Filter#getDocIdSet(org.apache.lucene.index.IndexReader)}. + */ +public final class EmptyDocIdSetIterator extends DocIdSetIterator { + + private static final DocIdSetIterator instance = new EmptyDocIdSetIterator(); + + public static DocIdSetIterator getInstance() { return instance; } + + // to prevent instantiation + private EmptyDocIdSetIterator() { } + + public int advance(int target) throws IOException { return NO_MORE_DOCS; } + + public int docID() { return NO_MORE_DOCS; } + + public int nextDoc() throws IOException { return NO_MORE_DOCS; } + +}