01: // ============================================================================
02: // $Id: Visitor.java,v 1.4 2006/01/08 00:52:25 davidahall Exp $
03: // Copyright (c) 2002-2005 David A. Hall
04: // ============================================================================
05: // The contents of this file are subject to the Common Development and
06: // Distribution License (CDDL), Version 1.0 (the License); you may not use this
07: // file except in compliance with the License. You should have received a copy
08: // of the the License along with this file: if not, a copy of the License is
09: // 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;
34:
35: /**
36: * Defines an interface for classes that may interpret functors or predicates.
37: * <p>
38: * jga uses the <a href="http://www.objectmentor.com/resources/articles/acv.pdf">AcyclicVisitor</a>
39: * pattern to provide a structure for implementing Visitor. Within jga, each
40: * class that implements Visitable does so with the following boilerplate:<br>
41: * <pre>
42: * public class Foo implements Visitable
43: * public void accept(net.sf.jga.fn.Visitor v) {
44: * if (v instanceof Foo.Visitor)
45: * ((Foo.Visitor)v).visit(this);
46: else
47: v.visit(this);
48: * }
49: *
50: * public interface Visitor extends net.sf.jga.fn.Visitor {
51: * public void visit(Foo host);
52: * }
53: * </pre>
54: * Implementations of Visitor will declare suport for a given class by
55: * implementing that class' Visitor interface.<br>
56: * <pre>
57: * public class FooBarCounter implements Foo.Visitor, Bar.Visitor {
58: * private int count = 0;
59: * public int getCount() { return count; }
60: * public void visit(Visitable host) {}
61: * public void visit(Foo host) { ++count; }
62: * public void visit(Bar host) { ++count; }
63: * }
64: * </pre>
65: * <p>
66: * Copyright © 2002-2005 David A. Hall
67: *
68: * @author <a href="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
69: **/
70:
71: public interface Visitor {
72: /**
73: * Call-back method, called by the Visitable object in response to a
74: * call to its <code>accept(Visitor)</code> method.
75: */
76: public void visit(Visitable visitable);
77: }
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