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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;
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 call(Context context,
100                        List 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 evaluate(Object obj) throws FunctionCallException
120     {
121       
122         if (obj instanceof List)
123         {
124             return new Double( ((List) obj).size() );
125         }
126       
127         throw new FunctionCallException("count() function can only be used for node-sets");
128         
129     }
130     
131 }