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Java > Open Source Codes > net > sf > jga > fn > adaptor > ConstantUnary


1 // ============================================================================
2 // $Id: ConstantUnary.java,v 1.7 2006/01/08 00:52:25 davidahall Exp $
3 // Copyright (c) 2003-2005 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.adaptor;
34
35 import net.sf.jga.fn.UnaryFunctor;
36     
37 /**
38  * Functor that returns the constant value given at construction.
39  * <p>
40  * To Serialize a ConstantUnary, the generic parameter V must be serializable.
41  * <p>
42  * Copyright &copy; 2003-2005 David A. Hall
43  *
44  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
45  */
46
47 public class ConstantUnary<T,V> extends UnaryFunctor<T,V> {
48
49     static final long serialVersionUID = 236974866552446215L;
50
51     // the constant value
52 private V _value;
53
54     /**
55      * Builds a Constant functor for the given value. The value may be null:
56      * in that case, evaluating the functor will return null.
57      */
58     public ConstantUnary (V val) {
59         _value = val;
60     }
61
62     // UnaryFunctor interface
63
64     /**
65      * Given one argument, summarily ignores it and returns the constant value
66      * given at construction. The argument will not be evaluated in any way by
67      * this functor.
68      *
69      * @return the constant value given at construction
70      */
71     
72     public V fn(T unused) {
73         return _value;
74     }
75
76     /**
77      * Calls the Visitor's <code>visit(ConstantUnary)</code> method, if it
78      * implements the nested Visitor interface.
79      */
80     public void accept(net.sf.jga.fn.Visitor v) {
81         if (v instanceof ConstantUnary.Visitor)
82             ((ConstantUnary.Visitor)v).visit(this);
83         else
84             v.visit(this);
85     }
86     
87     // Object overrides
88
89     public String JavaDoc toString() {
90         return "const " +_value;
91    }
92     
93      // AcyclicVisitor
94
95     /**
96      * Interface for classes that may interpret a <b>ConstantUnary</b> functor.
97      */
98     public interface Visitor extends net.sf.jga.fn.Visitor {
99         public void visit(ConstantUnary host);
100     }
101 }
102         
103
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