001: // ============================================================================
002: // $Id: Count.java,v 1.14 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:
033: package net.sf.jga.fn.algorithm;
034:
035: import java.util.Iterator;
036: import net.sf.jga.fn.UnaryFunctor;
037: import net.sf.jga.fn.comparison.Equality;
038: import net.sf.jga.fn.comparison.EqualTo;
039: import net.sf.jga.util.FindIterator;
040:
041: /**
042: * Counts values in an iteration.
043: * <p>
044: * Copyright © 2003-2005 David A. Hall
045: *
046: * @author <a href="mailto:davidahall@users.sf.net">David A. Hall</a>
047: */
048:
049: public class Count<T> extends UnaryFunctor<Iterator<? extends T>, Long> {
050:
051: static final long serialVersionUID = 5477750093695096889L;
052:
053: // the predicate used to determine if an element should be counted
054: private UnaryFunctor<T, Boolean> _eq;
055:
056: /**
057: * Builds a Count functor that counts instances of a specific value in an
058: * iteration, using the value's equals() method.
059: */
060: public Count(T value) {
061: this (new EqualTo<T>().bind2nd(value));
062: }
063:
064: /**
065: * Builds a Count functor that counts instances of a specific value in an
066: * iteration, using the given Equality predicate.
067: */
068: public Count(Equality<T> eq, T value) {
069: this (eq.bind2nd(value));
070: }
071:
072: /**
073: * Builds a Count functor that counts instances in an iteration for which
074: * the given predicate is true
075: */
076: public Count(UnaryFunctor<T, Boolean> eq) {
077: _eq = eq;
078: }
079:
080: /**
081: * Returns the predicate used to determine if an element should be counted.
082: */
083: public UnaryFunctor<T, Boolean> getComparisonFn() {
084: return _eq;
085: }
086:
087: /**
088: * Returns the number of elements in the iteration that meet the given
089: * criteria.
090: */
091: public Long fn(Iterator<? extends T> iterator) {
092: long count = 0;
093: FindIterator<T> finder = new FindIterator<T>(iterator);
094:
095: while (finder.findNext(_eq)) {
096: ++count;
097: finder.next();
098: }
099:
100: return new Long(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 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: }
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