| /* |
| 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.wiki.util; |
| |
| import java.util.AbstractList; |
| import java.util.ArrayList; |
| import java.util.Iterator; |
| import java.util.concurrent.locks.ReadWriteLock; |
| import java.util.concurrent.locks.ReentrantReadWriteLock; |
| |
| /** |
| * Provides a List in which all items store their addition time. This |
| * can then be used to clean the list from old items. |
| * <p> |
| * This class is thread-safe - all modifications are blocking, but |
| * reading is non-blocking (unless a write is ongoing). |
| * |
| * @param <T> The class you wish to store here |
| * @since 2.8 |
| */ |
| public class TimedCounterList<T> extends AbstractList<T> |
| { |
| private final ArrayList<CounterItem<T>> m_list = new ArrayList<CounterItem<T>>(); |
| private final ReadWriteLock m_lock = new ReentrantReadWriteLock(); |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public T set(final int index, final T element ) |
| { |
| m_lock.writeLock().lock(); |
| |
| T t; |
| |
| try |
| { |
| t = m_list.set(index,new CounterItem<T>(element)).m_obj; |
| } |
| finally |
| { |
| m_lock.writeLock().unlock(); |
| } |
| |
| return t; |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public T get(final int index ) |
| { |
| m_lock.readLock().lock(); |
| |
| T t; |
| |
| try |
| { |
| t = m_list.get(index).m_obj; |
| } |
| finally |
| { |
| m_lock.readLock().unlock(); |
| } |
| |
| return t; |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public int size() |
| { |
| m_lock.readLock().lock(); |
| int size = 0; |
| |
| try |
| { |
| size = m_list.size(); |
| } |
| finally |
| { |
| m_lock.readLock().unlock(); |
| } |
| |
| return size; |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public void add(final int index, final T element ) |
| { |
| m_lock.writeLock().lock(); |
| |
| try |
| { |
| m_list.add(index, new CounterItem<T>(element)); |
| } |
| finally |
| { |
| m_lock.writeLock().unlock(); |
| } |
| } |
| |
| /** |
| * {@inheritDoc} |
| */ |
| @Override |
| public T remove(final int index ) |
| { |
| m_lock.writeLock().lock(); |
| T t; |
| |
| try |
| { |
| t = m_list.remove( index ).m_obj; |
| } |
| finally |
| { |
| m_lock.writeLock().unlock(); |
| } |
| |
| return t; |
| } |
| |
| /** |
| * Returns the count how many times this object is available in |
| * this list, using equals(). |
| * |
| * @param obj The object to count. |
| * @return The count of the objects. |
| */ |
| public int count(final T obj ) |
| { |
| int c = 0; |
| m_lock.readLock().lock(); |
| |
| try |
| { |
| for( final CounterItem< T > i : m_list ) |
| { |
| if( i.m_obj.equals( obj ) ) |
| { |
| c++; |
| } |
| } |
| } |
| finally |
| { |
| m_lock.readLock().unlock(); |
| } |
| |
| return c; |
| } |
| |
| /** |
| * Performs a cleanup of all items older than maxage. |
| * |
| * @param maxage The maximum age in milliseconds after an item is removed. |
| */ |
| public void cleanup(final long maxage ) |
| { |
| m_lock.writeLock().lock(); |
| |
| try |
| { |
| final long now = System.currentTimeMillis(); |
| |
| for(final Iterator<CounterItem<T>> i = m_list.iterator(); i.hasNext(); ) |
| { |
| final CounterItem<T> ci = i.next(); |
| |
| final long age = now - ci.m_addTime; |
| |
| if( age > maxage ) |
| { |
| i.remove(); |
| } |
| } |
| } |
| finally |
| { |
| m_lock.writeLock().unlock(); |
| } |
| } |
| |
| /** |
| * Returns the time when this particular item was added on the list. |
| * |
| * @param index The index of the object. |
| * @return The addition time in milliseconds (@see System.currentTimeMillis()). |
| */ |
| public long getAddTime(final int index ) |
| { |
| m_lock.readLock().lock(); |
| long res = 0; |
| |
| try |
| { |
| res = m_list.get( index ).m_addTime; |
| } |
| finally |
| { |
| m_lock.readLock().unlock(); |
| } |
| |
| return res; |
| } |
| |
| private static class CounterItem<E> |
| { |
| private final E m_obj; |
| private final long m_addTime; |
| |
| public CounterItem(final E o) |
| { |
| m_addTime = System.currentTimeMillis(); |
| m_obj = o; |
| } |
| } |
| |
| |
| } |