01: // ============================================================================
02: // $Id: Visitable.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 be interpreted by a Visitor.
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 provides a nested interface called Visitor
41: * that defines a <code>visit</code> method for the class. This is typically
42: * implemented with the following boilerplate:<br>
43: * <pre>
44: * public class Foo implements Visitable
45: * public void accept(net.sf.jga.fn.Visitor v) {
46: * if (v instanceof Foo.Visitor)
47: * ((Foo.Visitor)v).visit(this);
48: else
49: v.visit(this);
50: * }
51: *
52: * public interface Visitor extends net.sf.jga.fn.Visitor {
53: * public void visit(Foo host);
54: * }
55: * </pre>
56: * <p>
57: * Copyright © 2002-2005 David A. Hall
58: *
59: * @author <a href="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
60: **/
61:
62: public interface Visitable {
63: /**
64: * Determine if the visitor is appropriate (typically by testing against
65: * a specific interface) and if so, call pass the implementing object to
66: * the visitor's visit method.
67: */
68: public void accept(Visitor visitor);
69: }
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