/*

  * 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.commons.pool.impl;

 import java.util.Timer;

 import java.util.TimerTask;

 /**

  * <p>

  * Provides a shared idle object eviction timer for all pools. This class wraps

  * the standard {@link Timer} and keeps track of how many pools are using it.

  * If no pools are using the timer, it is canceled. This prevents a thread

  * being left running which, in application server environments, can lead to

  * memory leads and/or prevent applications from shutting down or reloading

  * cleanly.

  * </p>

  * <p>

  * This class has package scope to prevent its inclusion in the pool public API.

  * The class declaration below should *not* be changed to public.

  * </p>

  */

 class EvictionTimer {

     /** Timer instance */

     private static Timer _timer;

     /** Static usage count tracker */

     private static int _usageCount;

     /** Prevent instantiation */

     private EvictionTimer() {

         // Hide the default constuctor

     }

     /**

      * Add the specified eviction task to the timer. Tasks that are added with a

      * call to this method *must* call {@link #cancel(TimerTask)} to cancel the

      * task to prevent memory and/or thread leaks in application server

      * environments.

      * @param task      Task to be scheduled

      * @param delay     Delay in milliseconds before task is executed

      * @param period    Time in milliseconds between executions

      */

     static synchronized void schedule(TimerTask task, long delay, long period) {

         if (null == _timer) {

             _timer = new Timer(true);

         }

         _usageCount++;

         _timer.schedule(task, delay, period);

     }

     /**

      * Remove the specified eviction task from the timer.

      * @param task      Task to be scheduled

      */

     static synchronized void cancel(TimerTask task) {

         task.cancel();

         _usageCount--;

         if (_usageCount == 0) {

             _timer.cancel();

             _timer = null;

         }

     }

 }