001: // ============================================================================
002: // $Id: ForEach.java,v 1.12 2006/01/08 00:52:25 davidahall Exp $
003: // Copyright (c) 2003-2005 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: package net.sf.jga.fn.algorithm;
033:
034: import java.util.Iterator;
035: import net.sf.jga.fn.UnaryFunctor;
036:
037: /**
038: * Applies a UnaryFunctor to each element in an iteration, and returns the
039: * final result. Each element in the iteration is passed to the functor in
040: * turn. The result of the final call to the functor is returned. If the
041: * iteration was empty, then the result of this function is null.
042: * <p>
043: * Copyright © 2003-2005 David A. Hall
044: *
045: * @author <a href="mailto:davidahall@users.sf.net">David A. Hall</a>
046: */
047:
048: public class ForEach<T, R> extends
049: UnaryFunctor<Iterator<? extends T>, R> {
050: static final long serialVersionUID = -2342252375909337974L;
051:
052: // The functor to be applied
053: private UnaryFunctor<T, R> _fn;
054:
055: /**
056: * Builds a ForEach functor that will use the given functor to process
057: * elements in an iteration.
058: * @throws IllegalArgumentException if the functor is null
059: */
060: public ForEach(UnaryFunctor<T, R> fn) {
061: if (fn == null)
062: throw new IllegalArgumentException();
063:
064: _fn = fn;
065: }
066:
067: /**
068: * Returns the functor used to process elements in an iteration.
069: */
070: public UnaryFunctor<T, R> getFunction() {
071: return _fn;
072: }
073:
074: /**
075: * Apply the functor to each element in the iteration and return the final
076: * result.
077: * @return the result of the last execution of the functor, or null if the
078: * functor is not executed.
079: */
080: public R fn(Iterator<? extends T> iterator) {
081: R value = null;
082: while (iterator.hasNext()) {
083: value = _fn.fn(iterator.next());
084: }
085:
086: return value;
087: }
088:
089: /**
090: * Calls the Visitor's <code>visit(ForEach)</code> method, if it
091: * implements the nested Visitor interface.
092: */
093: public void accept(net.sf.jga.fn.Visitor v) {
094: if (v instanceof ForEach.Visitor)
095: ((ForEach.Visitor) v).visit(this );
096: else
097: v.visit(this );
098: }
099:
100: // Object overrides
101:
102: public String toString() {
103: return "ForEach";
104: }
105:
106: // AcyclicVisitor
107:
108: /**
109: * Interface for classes that may interpret an <b>ForEach</b> functor.
110: */
111: public interface Visitor extends net.sf.jga.fn.Visitor {
112: public void visit(ForEach host);
113: }
114: }
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