content: /*
   * This library is part of OpenCms -
   * the Open Source Content Management System
   *
   * Copyright (c) Alkacon Software GmbH & Co. KG (https://www.alkacon.com)
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * This library is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
   * Lesser General Public License for more details.
   *
   * For further information about Alkacon Software, please see the
   * company website: https://www.alkacon.com
   *
   * For further information about OpenCms, please see the
   * project website: https://www.opencms.org
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, write to the Free Software
   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
   */
  
  package org.opencms.util;
  
  /**
   * Simple utility class for caching a single value with a given cache expiration time.<p>
   *
   * If the time between the last write operation and a read operation is longer than the expiration time,
   * null will be returned from the read operation.<p>
   *
   * @param <T> the type of the cached value
   */
  public class CmsExpiringValue<T> {
  
      /** The cached value. */
      private T m_value;
  
      /** Last time the value was set. */
      private long m_lastUpdate;
  
      /** The expiration time. */
      private long m_expirationTime;
  
      /**
       * Creates a new instance.<p>
       *
       * @param expirationTime the expiration time in milliseconds
       */
      public CmsExpiringValue(long expirationTime) {
          m_expirationTime = expirationTime;
      }
  
      /**
       * Gets the cached value.<p>
       *
       * Returns null if the last update was longer ago than the expiration time.
       *
       * @return the cached value
       */
      public synchronized T get() {
  
          if ((System.currentTimeMillis() - m_lastUpdate) > m_expirationTime) {
              return null;
          }
          return m_value;
      }
  
      /**
       * Sets the cached value.<p>
       *
       * @param value the cached value
       */
      public synchronized void set(T value) {
  
          m_lastUpdate = System.currentTimeMillis();
          m_value = value;
      }
  
  }
  