KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > net > sf > jga > fn > algorithm > Count


1 // ============================================================================
2 // $Id: Count.java,v 1.14 2006/01/08 00:52:25 davidahall Exp $
3 // Copyright (c) 2003-2005 David A. Hall
4 // ============================================================================
5 // The contents of this file are subject to the Common Development and
6 // Distribution License (CDDL), Version 1.0 (the License); you may not use this
7 // file except in compliance with the License. You should have received a copy
8 // of the the License along with this file: if not, a copy of the License is
9 // 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.algorithm;
34
35 import java.util.Iterator JavaDoc;
36 import net.sf.jga.fn.UnaryFunctor;
37 import net.sf.jga.fn.comparison.Equality;
38 import net.sf.jga.fn.comparison.EqualTo;
39 import net.sf.jga.util.FindIterator;
40
41 /**
42  * Counts values in an iteration.
43  * <p>
44  * Copyright &copy; 2003-2005 David A. Hall
45  *
46  * @author <a HREF="mailto:davidahall@users.sf.net">David A. Hall</a>
47  */
48
49 public class Count<T> extends UnaryFunctor<Iterator JavaDoc<? extends T>,Long JavaDoc> {
50
51     static final long serialVersionUID = 5477750093695096889L;
52     
53     // the predicate used to determine if an element should be counted
54 private UnaryFunctor<T,Boolean JavaDoc> _eq;
55
56     /**
57      * Builds a Count functor that counts instances of a specific value in an
58      * iteration, using the value's equals() method.
59      */
60     public Count (T value) {
61         this(new EqualTo<T>().bind2nd(value));
62     }
63     
64     /**
65      * Builds a Count functor that counts instances of a specific value in an
66      * iteration, using the given Equality predicate.
67      */
68     public Count (Equality<T> eq, T value) {
69         this(eq.bind2nd(value));
70     }
71
72     /**
73      * Builds a Count functor that counts instances in an iteration for which
74      * the given predicate is true
75      */
76     public Count (UnaryFunctor<T,Boolean JavaDoc> eq) {
77         _eq = eq;
78     }
79
80     /**
81      * Returns the predicate used to determine if an element should be counted.
82      */
83     public UnaryFunctor<T,Boolean JavaDoc> getComparisonFn() {
84         return _eq;
85     }
86
87     /**
88      * Returns the number of elements in the iteration that meet the given
89      * criteria.
90      */
91     public Long JavaDoc fn (Iterator JavaDoc<? extends T> iterator) {
92         long count = 0;
93         FindIterator<T> finder = new FindIterator<T>(iterator);
94         
95         while (finder.findNext(_eq)) {
96             ++count;
97             finder.next();
98         }
99      
100         return new Long JavaDoc(count);
101     }
102
103     /**
104      * Calls the Visitor's <code>visit(Count)</code> method, if it
105      * implements the nested Visitor interface.
106      */
107     public void accept(net.sf.jga.fn.Visitor v) {
108         if (v instanceof Count.Visitor)
109             ((Count.Visitor)v).visit(this);
110         else
111             v.visit(this);
112     }
113
114     // Object overrides
115
116     public String JavaDoc toString() {
117         return "Count["+_eq+"]";
118     }
119     
120     // AcyclicVisitor
121
122     /**
123      * Interface for classes that may interpret an <b>Count</b> functor.
124      */
125     public interface Visitor extends net.sf.jga.fn.Visitor {
126         public void visit(Count host);
127     }
128 }
129
Popular Tags