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Java > Open Source Codes > org > jaxen > function > SumFunction


1 /*
2  * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/SumFunction.java,v 1.9 2005/06/26 16:07:23 elharo Exp $
3  * $Revision: 1.9 $
4  * $Date: 2005/06/26 16:07:23 $
5  *
6  * ====================================================================
7  *
8  * Copyright (C) 2000-2002 bob mcwhirter & James Strachan.
9  * All rights reserved.
10  *
11  * Redistribution and use in source and binary forms, with or without
12  * modification, are permitted provided that the following conditions
13  * are met:
14  *
15  * 1. Redistributions of source code must retain the above copyright
16  * notice, this list of conditions, and the following disclaimer.
17  *
18  * 2. Redistributions in binary form must reproduce the above copyright
19  * notice, this list of conditions, and the disclaimer that follows
20  * these conditions in the documentation and/or other materials
21  * provided with the distribution.
22  *
23  * 3. The name "Jaxen" must not be used to endorse or promote products
24  * derived from this software without prior written permission. For
25  * written permission, please contact license@jaxen.org.
26  *
27  * 4. Products derived from this software may not be called "Jaxen", nor
28  * may "Jaxen" appear in their name, without prior written permission
29  * from the Jaxen Project Management (pm@jaxen.org).
30  *
31  * In addition, we request (but do not require) that you include in the
32  * end-user documentation provided with the redistribution and/or in the
33  * software itself an acknowledgement equivalent to the following:
34  * "This product includes software developed by the
35  * Jaxen Project (http://www.jaxen.org/)."
36  * Alternatively, the acknowledgment may be graphical using the logos
37  * available at http://www.jaxen.org/
38  *
39  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
40  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
41  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
42  * DISCLAIMED. IN NO EVENT SHALL THE Jaxen AUTHORS OR THE PROJECT
43  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
44  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
45  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
46  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
47  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
48  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
49  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
50  * SUCH DAMAGE.
51  *
52  * ====================================================================
53  * This software consists of voluntary contributions made by many
54  * individuals on behalf of the Jaxen Project and was originally
55  * created by bob mcwhirter <bob@werken.com> and
56  * James Strachan <jstrachan@apache.org>. For more information on the
57  * Jaxen Project, please see <http://www.jaxen.org/>.
58  *
59  * $Id: SumFunction.java,v 1.9 2005/06/26 16:07:23 elharo Exp $
60  */

61
62
63 package org.jaxen.function;
64
65 import java.util.Iterator JavaDoc;
66 import java.util.List JavaDoc;
67
68 import org.jaxen.Context;
69 import org.jaxen.Function;
70 import org.jaxen.FunctionCallException;
71 import org.jaxen.Navigator;
72
73 /**
74  * <p><b>4.4</b> <code><i>number</i> sum(<i>node-set</i>)</code> </p>
75  *
76  * <blockquote SRC="http://www.w3.org/TR/xpath#function-sum">
77  * The sum function returns the sum, for each node in the argument node-set,
78  * of the result of converting the string-values of the node to a number.
79  * </blockquote>
80  *
81  * @author bob mcwhirter (bob @ werken.com)
82  * @see <a HREF="http://www.w3.org/TR/xpath#function-sum" target="_top">Section 4.4 of the XPath Specification</a>
83  */

84 public class SumFunction implements Function
85 {
86
87     /**
88      * Create a new <code>SumFunction</code> object.
89      */

90     public SumFunction() {}
91     
92     /** Returns the sum of its arguments.
93      *
94      * @param context the context at the point in the
95      * expression when the function is called
96      * @param args a list that contains exactly one item, also a <code>List</code>
97      *
98      * @return a <code>Double</code> containing the sum of the items in <code>args.get(0)</code>
99      *
100      * @throws FunctionCallException if <code>args</code> has more or less than one item;
101      * or if the first argument is not a <code>List</code>
102      */

103     public Object JavaDoc call(Context context,
104                        List JavaDoc args) throws FunctionCallException
105     {
106
107         if (args.size() == 1)
108         {
109             return evaluate( args.get(0),
110                              context.getNavigator() );
111         }
112
113         throw new FunctionCallException( "sum() requires one argument." );
114     }
115
116     /**
117      * Returns the sum of the items in a list.
118      * If necessary, each item in the list is first converted to a <code>Double</code>
119      * as if by the XPath <code>number()</code> function.
120      *
121      * @param obj a <code>List</code> of numbers to be summed
122      * @param nav ignored
123      *
124      * @return the sum of the list
125      *
126      * @throws FunctionCallException if <code>obj</code> is not a <code>List</code>
127      */

128     public static Double JavaDoc evaluate(Object JavaDoc obj,
129                                   Navigator nav) throws FunctionCallException
130     {
131         double sum = 0;
132
133         if (obj instanceof List JavaDoc)
134         {
135             Iterator JavaDoc nodeIter = ((List JavaDoc)obj).iterator();
136             while ( nodeIter.hasNext() )
137             {
138                 double term = NumberFunction.evaluate( nodeIter.next(),
139                                                 nav ).doubleValue();
140                 sum += term;
141             }
142         }
143         else
144         {
145             throw new FunctionCallException("The argument to the sum function must be a node-set");
146         }
147
148         return new Double JavaDoc(sum);
149     }
150     
151 }
152
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