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Java > Open Source Codes > net > sf > jga > fn > logical > UnaryNegate


1 // ============================================================================
2 // $Id: UnaryNegate.java,v 1.14 2006/08/07 03:56:27 davidahall Exp $
3 // Copyright (c) 2002-2005 David A. Hall
4 // ============================================================================
5 // The contents of this file are subject to the Common Development and
6 // Distribution License (CDDL), Version 1.0 (the License); you may not use this
7 // file except in compliance with the License. You should have received a copy
8 // of the the License along with this file: if not, a copy of the License is
9 // available from Sun Microsystems, Inc.
10 //
11 // http://www.sun.com/cddl/cddl.html
12 //
13 // From time to time, the license steward (initially Sun Microsystems, Inc.) may
14 // publish revised and/or new versions of the License. You may not use,
15 // distribute, or otherwise make this file available under subsequent versions
16 // of the License.
17 //
18 // Alternatively, the contents of this file may be used under the terms of the
19 // GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
20 // case the provisions of the LGPL are applicable instead of those above. If you
21 // wish to allow use of your version of this file only under the terms of the
22 // LGPL, and not to allow others to use your version of this file under the
23 // terms of the CDDL, indicate your decision by deleting the provisions above
24 // and replace them with the notice and other provisions required by the LGPL.
25 // If you do not delete the provisions above, a recipient may use your version
26 // of this file under the terms of either the CDDL or the LGPL.
27 //
28 // This library is distributed in the hope that it will be useful,
29 // but WITHOUT ANY WARRANTY; without even the implied warranty of
30 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
31 // ============================================================================
32
33 package net.sf.jga.fn.logical;
34
35 import net.sf.jga.fn.UnaryPredicate;
36 import net.sf.jga.fn.UnaryFunctor;
37
38 /**
39  * Unary Predicate that logically negates the result of a child predicate.
40  * Returns true when child predicate <b>p</b> returns false given object
41  * argument <b>x</b>.
42  * <p>
43  * Copyright &copy; 2002-2005 David A. Hall
44  *
45  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
46  **/
47
48 public class UnaryNegate<T> extends UnaryPredicate<T> {
49
50     static final long serialVersionUID = -722445812960547108L;
51     
52     private UnaryFunctor<? super T, Boolean JavaDoc> _p;
53     
54     /**
55      * Builds a UnaryNegate predicate wrapping the given Unary Predicate.
56      * @throws IllegalArgumentException when no child predicate is given
57      */
58     public UnaryNegate(UnaryFunctor<? super T, Boolean JavaDoc> p) {
59         if (p == null) {
60             throw new IllegalArgumentException JavaDoc("Child Predicate may not be null");
61         }
62         
63         _p = p;
64     }
65
66     /**
67      * Returns the child predicate.
68      * @return the child predicate.
69      */
70     public UnaryFunctor<? super T,Boolean JavaDoc> getPredicate() { return _p; }
71
72     // UnaryPredicate interface
73
74     /**
75      * Given argument <b>x</b>, returns true when child
76      * predicate <b>p</b> returns false for x, otherwise returns true.
77      *
78      * @return !(p.p(x))
79      */
80     public Boolean JavaDoc fn(T x) {
81         return ! _p.fn(x);
82     }
83     
84     /**
85      * Calls the Visitor's <code>visit(UnaryNegate)</code> method, if it
86      * implements the nested Visitor interface.
87      */
88     public void accept(net.sf.jga.fn.Visitor v) {
89         if (v instanceof UnaryNegate.Visitor)
90             ((UnaryNegate.Visitor)v).visit(this);
91         else
92             v.visit(this);
93     }
94
95     // Object overrides
96
97     public String JavaDoc toString() {
98         return "UnaryNegate";
99     }
100     
101     // Acyclic Visitor
102
103     /**
104      * Interface for classes that may interpret a <b>UnaryNegate</b>
105      * predicate.
106      */
107     public interface Visitor extends net.sf.jga.fn.Visitor {
108         public void visit(UnaryNegate host);
109     }
110 }
111
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