001: // ============================================================================
002: // $Id: LessEqual.java,v 1.16 2006/01/08 00:52:25 davidahall Exp $
003: // Copyright (c) 2002-2005 David A. Hall
004: // ============================================================================
005: // The contents of this file are subject to the Common Development and
006: // Distribution License (CDDL), Version 1.0 (the License); you may not use this
007: // file except in compliance with the License. You should have received a copy
008: // of the the License along with this file: if not, a copy of the License is
009: // available from Sun Microsystems, Inc.
010: //
011: // http://www.sun.com/cddl/cddl.html
012: //
013: // From time to time, the license steward (initially Sun Microsystems, Inc.) may
014: // publish revised and/or new versions of the License. You may not use,
015: // distribute, or otherwise make this file available under subsequent versions
016: // of the License.
017: //
018: // Alternatively, the contents of this file may be used under the terms of the
019: // GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
020: // case the provisions of the LGPL are applicable instead of those above. If you
021: // wish to allow use of your version of this file only under the terms of the
022: // LGPL, and not to allow others to use your version of this file under the
023: // terms of the CDDL, indicate your decision by deleting the provisions above
024: // and replace them with the notice and other provisions required by the LGPL.
025: // If you do not delete the provisions above, a recipient may use your version
026: // of this file under the terms of either the CDDL or the LGPL.
027: //
028: // This library is distributed in the hope that it will be useful,
029: // but WITHOUT ANY WARRANTY; without even the implied warranty of
030: // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
031: // ============================================================================
032:
033: package net.sf.jga.fn.comparison;
034:
035: import java.util.Comparator;
036: import net.sf.jga.fn.BinaryPredicate;
037: import net.sf.jga.util.ComparableComparator;
038:
039: /**
040: * Binary Predicate that returns TRUE for arguments <b>x</b> and <b>y</b> when
041: * x <= y. The comparison is performed using a comparator supplied at
042: * construction time, although a default comparator will be used if the nested
043: * Comparable class' default constructor is used.
044: * The behaviour of this class in the presence of null arguments is left to the
045: * implementation of the specific Comparator, however it is generally safe to
046: * assume that using null arguments will cause a NullPointerException to be
047: * thrown.
048: * <p>
049: * To serialize a LessEqual predicate , the comparator passed at construction
050: * must be Serializable.
051: * <p>
052: * Copyright © 2002-2005 David A. Hall
053: *
054: * @author <a href="mailto:davidahall@users.sourceforge.net">David A. Hall</a>
055: **/
056:
057: public class LessEqual<T> extends BinaryPredicate<T, T> {
058:
059: static final long serialVersionUID = -4317901638908328747L;
060:
061: // The Comparator used to compare elements.
062: private Comparator/*@*/<? super T>/*@*/_comp;
063:
064: /**
065: * Builds a LessEqual predicate using the given Comparator.
066: * @throws IllegalArgumentException if the argument is null
067: */
068: public LessEqual(Comparator/*@*/<? super T>/*@*/comp) {
069: if (comp == null) {
070: throw new IllegalArgumentException(
071: "Comparator may not be null");
072: }
073:
074: _comp = comp;
075: }
076:
077: /**
078: * Returns the comparator in use by this functor
079: * @return the comparator in use by this functor
080: */
081: public Comparator<? super T> getComparator() {
082: return _comp;
083: }
084:
085: // BinaryPredicate interface
086:
087: /**
088: * Given Comparable arguments <b>x</b> and <b>y</b>, returns x <= y.
089: *
090: * @throws NullPointerException if either argument is null
091: * @return x <= y
092: */
093:
094: public Boolean fn(T x, T y) {
095: return Boolean.valueOf(_comp.compare(x, y) <= 0);
096: }
097:
098: /**
099: * Calls the Visitor's <code>visit(LessEqual)</code> method, if it
100: * implements the nested Visitor interface.
101: */
102: public void accept(net.sf.jga.fn.Visitor v) {
103: if (v instanceof LessEqual.Visitor)
104: ((LessEqual.Visitor) v).visit(this );
105: else
106: v.visit(this );
107: }
108:
109: // Object overrides
110:
111: public String toString() {
112: return "LessEqual";
113: }
114:
115: // Acyclic Visitor
116:
117: /**
118: * Interface for classes that may interpret a <b>LessEqual</b> predicate.
119: */
120: public interface Visitor extends net.sf.jga.fn.Visitor {
121: public void visit(LessEqual host);
122: }
123:
124: /**
125: * LessEqual predicate for use with Comparable arguments. This class exists
126: * as an implementation detail that works around a limit in the javac
127: * inferencer -- in all substantive ways, this is simply a LessEqual functor.
128: */
129:
130: static public class Comparable<T extends java.lang.Comparable/*@*/<? super T>/*@*/>
131: extends LessEqual<T> {
132: static final long serialVersionUID = 2318301997226073587L;
133:
134: public Comparable() {
135: super (new ComparableComparator<T>());
136: }
137: }
138: }
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