| /*- |
| * 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. |
| */ |
| |
| package org.apache.sling.query.impl.iterator; |
| |
| import java.util.Collections; |
| import java.util.HashSet; |
| import java.util.Iterator; |
| import java.util.Set; |
| |
| import org.apache.sling.query.api.internal.Option; |
| |
| /** |
| * Provides an iteration of unique objects. During the iteration process this |
| * iterator maintains a {@link HashSet} of previously seen items that will be |
| * used as filter to prevent duplicates |
| * |
| * @param <T> |
| */ |
| public class UniqueIterator<T> extends AbstractIterator<Option<T>> { |
| |
| private Iterator<Option<T>> iterator; |
| |
| private Set<T> seen; |
| |
| public UniqueIterator(Iterator<Option<T>> input) { |
| this.iterator = input; |
| seen = new HashSet<>(); |
| } |
| |
| @Override |
| protected Option<T> getElement() { |
| if (!iterator.hasNext()) { |
| iterator = Collections.emptyIterator(); |
| seen = null; |
| return null; |
| } |
| Option<T> candidate = iterator.next(); |
| if (!candidate.isEmpty()) { |
| if (!seen.add(candidate.getElement())) { |
| return Option.empty(candidate.getArgumentId()); |
| } |
| } |
| return candidate; |
| } |
| |
| } |