01: // ============================================================================
02: // $Id: GenericComparator.java,v 1.5 2005/08/02 23:45:22 davidahall Exp $
03: // Copyright (c) 2003-2005 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: package net.sf.jga.util;
33:
34: import net.sf.jga.fn.UnaryFunctor;
35: import java.io.Serializable;
36: import java.util.Comparator;
37:
38: /**
39: * Comparator that applies a functor to each argument, then compares the
40: * results. The functor must return Comparable values.
41: * <p>
42: * Copyright © 2003-2005 David A. Hall
43: *
44: * @author <a href="mailto:davidahall@users.sf.net">David A. Hall</a>
45: */
46:
47: public class GenericComparator<T, R extends Comparable<? super R>>
48: implements Comparator<T>, Serializable {
49:
50: static final long serialVersionUID = -2163248795946764874L;
51:
52: // The functor applied to both arguments in order to yield the value to be compared
53: private UnaryFunctor<T, R> _fn;
54:
55: /**
56: * Builds a comparator that uses the given functor to derive the values that are to
57: * be compared.
58: */
59: public GenericComparator(UnaryFunctor<T, R> fn) {
60: if (fn == null)
61: throw new IllegalArgumentException("Functor is required");
62:
63: _fn = fn;
64: }
65:
66: /**
67: * Applies the functor to each of the two arguments, and compares the results.
68: */
69: public int compare(T x, T y) {
70: return _fn.fn(x).compareTo(_fn.fn(y));
71: }
72: }
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