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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    */
IteratorPool(DTMIterator original)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    */
getInstanceOrThrow()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    */
getInstance()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    */
freeInstance(DTMIterator obj)115   public synchronized void freeInstance(DTMIterator obj)
116   {
117     m_freeStack.add(obj);
118   }
119 }
120