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


1 // ============================================================================
2 // $Id: ForEach.java,v 1.12 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 package net.sf.jga.fn.algorithm;
33
34 import java.util.Iterator JavaDoc;
35 import net.sf.jga.fn.UnaryFunctor;
36
37 /**
38  * Applies a UnaryFunctor to each element in an iteration, and returns the
39  * final result. Each element in the iteration is passed to the functor in
40  * turn. The result of the final call to the functor is returned. If the
41  * iteration was empty, then the result of this function is null.
42  * <p>
43  * Copyright &copy; 2003-2005 David A. Hall
44  *
45  * @author <a HREF="mailto:davidahall@users.sf.net">David A. Hall</a>
46  */
47
48 public class ForEach<T,R> extends UnaryFunctor<Iterator JavaDoc<? extends T>, R> {
49     static final long serialVersionUID = -2342252375909337974L;
50
51     // The functor to be applied
52 private UnaryFunctor<T,R> _fn;
53
54     /**
55      * Builds a ForEach functor that will use the given functor to process
56      * elements in an iteration.
57      * @throws IllegalArgumentException if the functor is null
58      */
59     public ForEach(UnaryFunctor<T,R> fn) {
60         if (fn == null)
61             throw new IllegalArgumentException JavaDoc();
62         
63         _fn = fn;
64     }
65
66     /**
67      * Returns the functor used to process elements in an iteration.
68      */
69     public UnaryFunctor<T,R> getFunction() {
70         return _fn;
71     }
72
73     /**
74      * Apply the functor to each element in the iteration and return the final
75      * result.
76      * @return the result of the last execution of the functor, or null if the
77      * functor is not executed.
78      */
79     public R fn(Iterator JavaDoc<? extends T> iterator) {
80         R value = null;
81         while (iterator.hasNext()) {
82             value = _fn.fn(iterator.next());
83         }
84
85         return value;
86     }
87     
88     /**
89      * Calls the Visitor's <code>visit(ForEach)</code> method, if it
90      * implements the nested Visitor interface.
91      */
92     public void accept(net.sf.jga.fn.Visitor v) {
93         if (v instanceof ForEach.Visitor)
94             ((ForEach.Visitor)v).visit(this);
95         else
96             v.visit(this);
97     }
98
99     // Object overrides
100
101     public String JavaDoc toString() {
102         return "ForEach";
103     }
104     
105     // AcyclicVisitor
106
107     /**
108      * Interface for classes that may interpret an <b>ForEach</b> functor.
109      */
110     public interface Visitor extends net.sf.jga.fn.Visitor {
111         public void visit(ForEach host);
112     }
113 }
114
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