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      1 /*
      2  * Licensed to the Apache Software Foundation (ASF) under one
      3  * or more contributor license agreements. See the NOTICE file
      4  * distributed with this work for additional information
      5  * regarding copyright ownership. The ASF licenses this file
      6  * to you under the Apache License, Version 2.0 (the  "License");
      7  * you may not use this file except in compliance with the License.
      8  * You may obtain a copy of the License at
      9  *
     10  *     http://www.apache.org/licenses/LICENSE-2.0
     11  *
     12  * Unless required by applicable law or agreed to in writing, software
     13  * distributed under the License is distributed on an "AS IS" BASIS,
     14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     15  * See the License for the specific language governing permissions and
     16  * limitations under the License.
     17  */
     18 /*
     19  * $Id: IteratorPool.java 475981 2006-11-16 23:35:53Z minchau $
     20  */
     21 package org.apache.xpath.axes;
     22 
     23 import java.util.ArrayList;
     24 
     25 import org.apache.xml.dtm.DTMIterator;
     26 import org.apache.xml.utils.WrappedRuntimeException;
     27 
     28 /**
     29  * Pool of object of a given type to pick from to help memory usage
     30  * @xsl.usage internal
     31  */
     32 public final class IteratorPool implements java.io.Serializable
     33 {
     34     static final long serialVersionUID = -460927331149566998L;
     35 
     36   /**
     37    * Type of objects in this pool.
     38    */
     39   private final DTMIterator m_orig;
     40 
     41   /**
     42    * Stack of given objects this points to.
     43    */
     44   private final ArrayList m_freeStack;
     45 
     46   /**
     47    * Constructor IteratorPool
     48    *
     49    * @param original The original iterator from which all others will be cloned.
     50    */
     51   public IteratorPool(DTMIterator original)
     52   {
     53     m_orig = original;
     54     m_freeStack = new ArrayList();
     55   }
     56 
     57   /**
     58    * Get an instance of the given object in this pool
     59    *
     60    * @return An instance of the given object
     61    */
     62   public synchronized DTMIterator getInstanceOrThrow()
     63     throws CloneNotSupportedException
     64   {
     65     // Check if the pool is empty.
     66     if (m_freeStack.isEmpty())
     67     {
     68 
     69       // Create a new object if so.
     70       return (DTMIterator)m_orig.clone();
     71     }
     72     else
     73     {
     74       // Remove object from end of free pool.
     75       DTMIterator result = (DTMIterator)m_freeStack.remove(m_freeStack.size() - 1);
     76       return result;
     77     }
     78   }
     79 
     80   /**
     81    * Get an instance of the given object in this pool
     82    *
     83    * @return An instance of the given object
     84    */
     85   public synchronized DTMIterator getInstance()
     86   {
     87     // Check if the pool is empty.
     88     if (m_freeStack.isEmpty())
     89     {
     90 
     91       // Create a new object if so.
     92       try
     93       {
     94         return (DTMIterator)m_orig.clone();
     95       }
     96       catch (Exception ex)
     97       {
     98         throw new WrappedRuntimeException(ex);
     99       }
    100     }
    101     else
    102     {
    103       // Remove object from end of free pool.
    104       DTMIterator result = (DTMIterator)m_freeStack.remove(m_freeStack.size() - 1);
    105       return result;
    106     }
    107   }
    108 
    109   /**
    110    * Add an instance of the given object to the pool
    111    *
    112    *
    113    * @param obj Object to add.
    114    */
    115   public synchronized void freeInstance(DTMIterator obj)
    116   {
    117     m_freeStack.add(obj);
    118   }
    119 }
    120