| /* |
| * 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.iotdb.db.utils; |
| |
| import java.util.ArrayList; |
| import java.util.Iterator; |
| import java.util.LinkedList; |
| import java.util.List; |
| |
| /** |
| * this class can just guarantee some behavior in a concurrent thread safety mode: |
| * |
| * @param <T> |
| */ |
| public class CopyOnReadLinkedList<T> { |
| |
| LinkedList<T> data = new LinkedList<>(); |
| List<T> readCopy; |
| |
| public synchronized void add(T d) { |
| data.add(d); |
| } |
| |
| public synchronized boolean contains(T d) { |
| return data.contains(d); |
| } |
| |
| public synchronized void remove(T d) { |
| data.remove(d); |
| } |
| |
| public synchronized Iterator<T> iterator() { |
| readCopy = new ArrayList<>(data); |
| return readCopy.iterator(); |
| } |
| |
| public synchronized void reset() { |
| readCopy = null; |
| } |
| |
| public synchronized List<T> cloneList() { |
| if (readCopy == null) { |
| readCopy = new ArrayList<>(data); |
| } |
| return readCopy; |
| } |
| |
| public boolean isEmpty() { |
| return size() == 0; |
| } |
| |
| public int size() { |
| return data.size(); |
| } |
| } |