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1   /*
2    * $Header: /home/projects/jaxen/scm/jaxen/src/java/main/org/jaxen/function/CountFunction.java,v 1.14 2006/02/05 21:47:41 elharo Exp $
3    * $Revision: 1.14 $
4    * $Date: 2006/02/05 21:47:41 $
5    *
6    * ====================================================================
7    *
8    * Copyright 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 are
13   * met:
14   * 
15   *   * Redistributions of source code must retain the above copyright
16   *     notice, this list of conditions and the following disclaimer.
17   * 
18   *   * Redistributions in binary form must reproduce the above copyright
19   *     notice, this list of conditions and the following disclaimer in the
20   *     documentation and/or other materials provided with the distribution.
21   * 
22   *   * Neither the name of the Jaxen Project nor the names of its
23   *     contributors may be used to endorse or promote products derived 
24   *     from this software without specific prior written permission.
25   * 
26   * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
27   * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28   * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
29   * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
30   * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
31   * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
32   * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
33   * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
34   * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
35   * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
36   * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
37   *
38   * ====================================================================
39   * This software consists of voluntary contributions made by many 
40   * individuals on behalf of the Jaxen Project and was originally 
41   * created by bob mcwhirter <bob@werken.com> and 
42   * James Strachan <jstrachan@apache.org>.  For more information on the 
43   * Jaxen Project, please see <http://www.jaxen.org/>.
44   * 
45   * $Id: CountFunction.java,v 1.14 2006/02/05 21:47:41 elharo Exp $
46   */
47  
48  package org.jaxen.function;
49  
50  import java.util.List;
51  
52  import org.jaxen.Context;
53  import org.jaxen.Function;
54  import org.jaxen.FunctionCallException;
55  
56  /***
57   *  <p><b>4.1</b> <code><i>number</i> count(<i>node-set</i>)</code></p> 
58   *  
59   * <blockquote src="http://www.w3.org/TR/xpath#function-count">
60   * The <b>count</b> function returns the number of nodes in the argument node-set.
61   * </blockquote>
62   * @author bob mcwhirter (bob @ werken.com)
63   * @see <a href="http://www.w3.org/TR/xpath#function-count">Section 4.1 of the XPath Specification</a>
64   */
65  public class CountFunction implements Function
66  {
67  
68      /***
69       * Create a new <code>CountFunction</code> object.
70       */
71      public CountFunction() {}
72      
73      /***
74       * <p>
75       * Returns the number of nodes in the specified node-set.
76       * </p>
77       * @param context ignored
78       * @param args the function arguments
79       * 
80       * @return a <code>Double</code> giving the integral number of items in the first argument
81       * 
82       * @throws FunctionCallException if args does not have exactly one 
83       *     item; or that item is not a <code>List</code>
84       */
85      public Object call(Context context,
86                         List args) throws FunctionCallException
87      {
88          if (args.size() == 1)
89          {
90              return evaluate( args.get(0) );
91          }
92  
93          throw new FunctionCallException( "count() requires one argument." );
94      }
95  
96      /***
97       * <p>
98       * Returns the number of nodes in the specified node-set.
99       * </p>
100      * 
101      * @param obj a <code>List</code> of nodes
102      * @return the integral number of items in the list
103      * @throws FunctionCallException if obj is not a <code>List</code>
104      */
105     public static Double evaluate(Object obj) throws FunctionCallException
106     {
107       
108         if (obj instanceof List)
109         {
110             return new Double( ((List) obj).size() );
111         }
112       
113         throw new FunctionCallException("count() function can only be used for node-sets");
114         
115     }
116     
117 }