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


1 /*
2  * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/CountFunction.java,v 1.11 2005/06/26 16:07:22 elharo Exp $
3  * $Revision: 1.11 $
4  * $Date: 2005/06/26 16:07:22 $
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: CountFunction.java,v 1.11 2005/06/26 16:07:22 elharo Exp $
60  */
61
62 package org.jaxen.function;
63
64 import java.util.List JavaDoc;
65
66 import org.jaxen.Context;
67 import org.jaxen.Function;
68 import org.jaxen.FunctionCallException;
69
70 /**
71  * <p><b>4.1</b> <code><i>number</i> count(<i>node-set</i>)</code>
72  *
73  * <blockquote SRC="http://www.w3.org/TR/xpath#function-count">
74  * The <b>count</b> function returns the number of nodes in the argument node-set.
75  * </blockquote>
76  * @author bob mcwhirter (bob @ werken.com)
77  * @see <a HREF="http://www.w3.org/TR/xpath#function-count">Section 4.1 of the XPath Specification</a>
78  */
79 public class CountFunction implements Function
80 {
81
82     /**
83      * Create a new <code>CountFunction</code> object.
84      */
85     public CountFunction() {}
86     
87     /**
88      * <p>
89      * Returns the number of nodes in the specified node-set.
90      * </p>
91      * @param context ignored
92      * @param args the function arguments
93      *
94      * @return a <code>Double</code> giving the integral number of items in the first argument
95      *
96      * @throws FunctionCallException if args does not have exactly one
97      * item; or that item is not a <code>List</code>
98      */
99     public Object JavaDoc call(Context context,
100                        List JavaDoc args) throws FunctionCallException
101     {
102         if (args.size() == 1)
103         {
104             return evaluate( args.get(0) );
105         }
106
107         throw new FunctionCallException( "count() requires one argument." );
108     }
109
110     /**
111      * <p>
112      * Returns the number of nodes in the specified node-set.
113      * </p>
114      *
115      * @param obj a <code>List</code> of nodes
116      * @return the integral number of items in the list
117      * @throws FunctionCallException if obj is not a <code>List</code>
118      */
119     public static Double JavaDoc evaluate(Object JavaDoc obj) throws FunctionCallException
120     {
121       
122         if (obj instanceof List JavaDoc)
123         {
124             return new Double JavaDoc( ((List JavaDoc) obj).size() );
125         }
126       
127         throw new FunctionCallException("count() function can only be used for node-sets");
128         
129     }
130     
131 }
132
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