1 /*
2 * $Header$
3 * $Revision$
4 * $Date$
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 * $Id$
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 import org.jaxen.Navigator;
56
57 /**
58 * <p><b>4.3</b> <code><i>boolean</i> not(<i>boolean</i>)</code> </p>
59 *
60 *
61 * <blockquote cite="http://www.w3.org/TR/xpath#function-not">
62 * The <b>not</b> function returns true if its argument is false, and false otherwise.
63 * </blockquote>
64 *
65 * @author bob mcwhirter (bob @ werken.com)
66 * @see <a href="https://www.w3.org/TR/xpath#function-not" target="_top">Section 4.3 of the XPath Specification</a>
67 */
68 public class NotFunction implements Function
69 {
70
71 /**
72 * Create a new <code>NotFunction</code> object.
73 */
74 public NotFunction() {}
75
76 /**
77 * Returns <code>Boolean.TRUE</code> if the boolean value of
78 * <code>args.get(0)</code> is false, and <code>Boolean.FALSE</code> otherwise.
79 * The boolean value is calculated as if by the XPath <code>boolean</code>
80 * function.
81 *
82 * @param context the context at the point in the
83 * expression where the function is called
84 * @param args a single element list
85 *
86 * @return <code>Boolean.TRUE</code> if the boolean value of
87 * <code>obj</code> is false, and <code>Boolean.FALSE</code> otherwise
88 *
89 * @throws FunctionCallException if <code>args</code> does not have exactly one argument
90 */
91 public Object call(Context context,
92 List args) throws FunctionCallException
93 {
94 if (args.size() == 1)
95 {
96 return evaluate( args.get(0), context.getNavigator() );
97 }
98
99 throw new FunctionCallException( "not() requires one argument." );
100 }
101
102 /**
103 * Returns <code>Boolean.TRUE</code> if the boolean value of
104 * <code>obj</code> is false, and <code>Boolean.FALSE</code> otherwise.
105 * The boolean value is calculated as if by the XPath <code>boolean</code>
106 * function.
107 *
108 * @param obj the object whose boolean value is inverted
109 * @param nav the <code>Navigator</code> used to calculate the boolean value of <code>obj</code>
110 *
111 * @return <code>Boolean.TRUE</code> if the boolean value of
112 * <code>obj</code> is false, and <code>Boolean.FALSE</code> otherwise
113 */
114 public static Boolean evaluate(Object obj, Navigator nav)
115 {
116 return ( ( BooleanFunction.evaluate( obj, nav ).booleanValue() )
117 ? Boolean.FALSE
118 : Boolean.TRUE
119 );
120 }
121
122 }