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Java > Open Source Codes > org > apache > xml > dtm > ref > CustomStringPool


1 /*
2  * Copyright 1999-2004 The Apache Software Foundation.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  * http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 /*
17  * $Id: CustomStringPool.java,v 1.5 2004/02/16 23:06:11 minchau Exp $
18  */
19
20 package org.apache.xml.dtm.ref;
21 import java.util.Hashtable JavaDoc;
22
23 /** <p>CustomStringPool is an example of appliction provided data structure
24  * for a DTM implementation to hold symbol references, e.g. elelment names.
25  * It will follow the DTMDStringPool interface and use two simple methods
26  * indexToString(int i) and stringToIndex(Sring s) to map between a set of
27  * string values and a set of integer index values. Therefore, an application
28  * may improve DTM processing speed by substituting the DTM symbol resolution
29  * tables with application specific quick symbol resolution tables.</p>
30  *
31  * %REVIEW% The only difference between this an DTMStringPool seems to be that
32  * it uses a java.lang.Hashtable full of Integers rather than implementing its
33  * own hashing. Joe deliberately avoided that approach when writing
34  * DTMStringPool, since it is both much more memory-hungry and probably slower
35  * -- especially in JDK 1.1.x, where Hashtable is synchronized. We need to
36  * either justify this implementation or discard it.
37  *
38  * <p>Status: In progress, under discussion.</p>
39  * */
40 public class CustomStringPool extends DTMStringPool {
41         //final Vector m_intToString;
42 //static final int HASHPRIME=101;
43 //int[] m_hashStart=new int[HASHPRIME];
44 final Hashtable JavaDoc m_stringToInt = new Hashtable JavaDoc();
45         public static final int NULL=-1;
46
47         public CustomStringPool()
48         {
49                 super();
50                 /*m_intToString=new Vector();
51                 System.out.println("In constructor m_intToString is " +
52                                                                                          ((null == m_intToString) ? "null" : "not null"));*/
53                 //m_stringToInt=new Hashtable();
54 //removeAllElements();
55 }
56
57         public void removeAllElements()
58         {
59                 m_intToString.removeAllElements();
60                 if (m_stringToInt != null)
61                         m_stringToInt.clear();
62         }
63
64         /** @return string whose value is uniquely identified by this integer index.
65          * @throws java.lang.ArrayIndexOutOfBoundsException
66          * if index doesn't map to a string.
67          * */
68         public String JavaDoc indexToString(int i)
69         throws java.lang.ArrayIndexOutOfBoundsException JavaDoc
70         {
71                 return(String JavaDoc) m_intToString.elementAt(i);
72         }
73
74         /** @return integer index uniquely identifying the value of this string. */
75         public int stringToIndex(String JavaDoc s)
76         {
77                 if (s==null) return NULL;
78                 Integer JavaDoc iobj=(Integer JavaDoc)m_stringToInt.get(s);
79                 if (iobj==null) {
80                         m_intToString.addElement(s);
81                         iobj=new Integer JavaDoc(m_intToString.size());
82                         m_stringToInt.put(s,iobj);
83                 }
84                 return iobj.intValue();
85         }
86 }
87
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