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


1 // ============================================================================
2 // $Id: Identity.java,v 1.9 2006/01/08 00:52:25 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.adaptor;
34
35 import net.sf.jga.fn.UnaryFunctor;
36     
37 /**
38  * Unary Functor that returns the runtime argument.
39  * <p>
40  * Copyright &copy; 2002-2005 David A. Hall
41  *
42  * @author <a HREF="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
43  */
44
45 public class Identity<T> extends UnaryFunctor<T, T> {
46     
47     static final long serialVersionUID = -1170897535180697025L;
48
49     // the last value passed to fn()
50 private transient T _last;
51     
52     /**
53      * Returns the last argument that was given, or null if called prior to the
54      * first call to fn(). This value does not persist when the functor is
55      * serialized.
56      *
57      * @return the last argument that was given or null.
58      */
59     public T arg() {
60         return _last;
61     }
62     
63     // UnaryFunctor interface
64
65     /**
66      * Given one argument, returns it.
67      *
68      * @return x
69      */
70     public T fn(T x) {
71         _last = x;
72         return x;
73     }
74
75     /**
76      * Calls the Visitor's <code>visit(Identity)</code> method, if it
77      * implements the nested Visitor interface.
78      */
79     public void accept(net.sf.jga.fn.Visitor v) {
80         if (v instanceof Identity.Visitor)
81             ((Identity.Visitor)v).visit(this);
82         else
83             v.visit(this);
84     }
85
86     // Object overrides
87
88     public String JavaDoc toString() {
89         return "Identity";
90     }
91     
92      // AcyclicVisitor
93
94     /**
95      * Interface for classes that may interpret an <b>Identity</b> functor.
96      */
97     public interface Visitor extends net.sf.jga.fn.Visitor {
98         public void visit(Identity host);
99     }
100 }
101         
102
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