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


1 // ============================================================================
2 // $Id: Constant.java,v 1.13 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.Generator;
36
37 /**
38  * Functor that returns the constant value given at construction.
39  * <p>
40  * Copyright &copy; 2003-2005 David A. Hall
41  *
42  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
43  */
44
45 public class Constant<V> extends Generator<V> {
46
47     static final long serialVersionUID = 8451989044496281343L;
48
49     private V _value;
50
51     /**
52      * Builds a Constant functor for the given value. The value may be null:
53      * in that case, evaluating the functor will return null.
54      */
55     public Constant (V val) {
56         _value = val;
57     }
58
59
60     // Generator interface
61
62     /**
63      * Returns the constant value given at construction
64      * @return the constant value given at construction
65      */
66     
67     public V gen() {
68         return _value;
69     }
70
71     /**
72      * Calls the Visitor's <code>visit(Constant)</code> method, if it
73      * implements the nested Visitor interface.
74      */
75     public void accept(net.sf.jga.fn.Visitor v) {
76         if (v instanceof Constant.Visitor)
77             ((Constant.Visitor)v).visit(this);
78         else
79             v.visit(this);
80     }
81     
82     // Object overrides
83
84     public String JavaDoc toString() {
85         return "const " +_value;
86     }
87     
88      // AcyclicVisitor
89
90     /**
91      * Interface for classes that may interpret a <b>Constant</b> generator.
92      */
93     public interface Visitor extends net.sf.jga.fn.Visitor {
94         public void visit(Constant host);
95     }
96 }
97         
98
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