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Java > Open Source Codes > net > sf > jga > fn > arithmetic > Average


1 // ============================================================================
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// $Id: Average.java,v 1.3 2006/01/08 00:52:25 davidahall Exp $
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// Copyright (c) 2005 David A. Hall
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// ============================================================================
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// The contents of this file are subject to the Common Development and
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// Distribution License (CDDL), Version 1.0 (the License); you may not use this
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// file except in compliance with the License. You should have received a copy
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// of the the License along with this file: if not, a copy of the License is
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// available from Sun Microsystems, Inc.
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//
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// http://www.sun.com/cddl/cddl.html
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//
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// From time to time, the license steward (initially Sun Microsystems, Inc.) may
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// publish revised and/or new versions of the License. You may not use,
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// distribute, or otherwise make this file available under subsequent versions
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// of the License.
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//
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// Alternatively, the contents of this file may be used under the terms of the
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// GNU Lesser General Public License Version 2.1 or later (the "LGPL"), in which
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// case the provisions of the LGPL are applicable instead of those above. If you
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// wish to allow use of your version of this file only under the terms of the
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// LGPL, and not to allow others to use your version of this file under the
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// terms of the CDDL, indicate your decision by deleting the provisions above
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// and replace them with the notice and other provisions required by the LGPL.
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// If you do not delete the provisions above, a recipient may use your version
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// of this file under the terms of either the CDDL or the LGPL.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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// ============================================================================
32

33 package net.sf.jga.fn.arithmetic;
34
35 import java.text.MessageFormat JavaDoc;
36 import java.util.Iterator JavaDoc;
37 import net.sf.jga.fn.UnaryFunctor;
38
39 /**
40  * Averages numeric values in an iteration.
41  * <p>
42  * Copyright &copy; 2005 David A. Hall
43  *
44  * @author <a HREF="mailto:davidahall@users.sf.net">David A. Hall</a>
45  */

46
47 public class Average<T extends Number JavaDoc> extends UnaryFunctor<Iterator JavaDoc<T>,T> {
48
49     static final long serialVersionUID = -8341653586442484621L;
50     
51     // Utility class that performs the addition as appropriate for the
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// class given at construction
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private Arithmetic<T> _math;
54
55     /**
56      * Builds a functor that averages numeric values in an iteration
57      */

58     public Average(Class JavaDoc<T> type) {
59          _math = ArithmeticFactory.getArithmetic(type);
60          if (_math == null) {
61              String JavaDoc msg = "No implementation of Arithmetic registered for {0}";
62              throw new IllegalArgumentException JavaDoc(MessageFormat.format(msg, new Object JavaDoc[]{type}));
63          }
64     }
65     
66     /**
67      * Returns the average of the elements in the iteration
68      */

69     public T fn (Iterator JavaDoc<T> iterator) {
70         int count = 0;
71         T sum = _math.zero();
72         
73         while (iterator.hasNext()) {
74             T value = iterator.next();
75             sum = _math.plus(sum, value);
76             ++count;
77         }
78      
79         return _math.divides(sum, _math.valueOf(count));
80     }
81
82     /**
83      * Calls the Visitor's <code>visit(Average)</code> method, if it
84      * implements the nested Visitor interface.
85      */

86     public void accept(net.sf.jga.fn.Visitor v) {
87         if (v instanceof Average.Visitor)
88             ((Average.Visitor)v).visit(this);
89         else
90             v.visit(this);
91     }
92
93     // Object overrides
94

95     public String JavaDoc toString() {
96         return "Average[]";
97     }
98     
99     // AcyclicVisitor
100

101     /**
102      * Interface for classes that may interpret an <b>Average</b> functor.
103      */

104     public interface Visitor extends net.sf.jga.fn.Visitor {
105         public void visit(Average host);
106     }
107 }
108
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