01: // ============================================================================
02: // $Id: IteratorComparator.java,v 1.9 2005/08/02 23:45:22 davidahall Exp $
03: // Copyright (c) 2003-2005 David A. Hall
04: // ============================================================================
05: // The contents of this file are subject to the Common Development and
06: // Distribution License (CDDL), Version 1.0 (the License); you may not use this
07: // file except in compliance with the License. You should have received a copy
08: // of the the License along with this file: if not, a copy of the License is
09: // 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.util;
34:
35: import java.io.Serializable;
36: import java.util.Comparator;
37: import java.util.Iterator;
38: import net.sf.jga.fn.comparison.Equality;
39:
40: /**
41: * Comparator used to compare iterations lexically.
42: *
43: * @author <a href="mailto:davidahall@users.sf.net">David A. Hall</a>
44: */
45:
46: public class IteratorComparator<T> implements
47: Comparator<Iterator<? extends T>>, Serializable {
48:
49: static final long serialVersionUID = 1110218880817939318L;
50:
51: // The comparator used to compare the elements of the two argument comparators
52: private Comparator<? super T> _comp;
53:
54: /**
55: * Builds an IteratorComparator that uses the given Comparator to compare
56: * the elements of an iteration.
57: */
58: public IteratorComparator(Comparator<? super T> comp) {
59: _comp = comp;
60: }
61:
62: /**
63: * Compares the contents of the two iterations. An element from each
64: * iteration is passed to the given comparator, and if they are not equal,
65: * the iteration that produced the lesser of the two elements is determined
66: * to be the lesser of the two iterations. If the elements are equal, then
67: * the next pair of elements if passed. If one of the two iterations is
68: * exhausted before a pair of unequal elements is found, then it is
69: * considered to be the lesser. If both iterations are exhausted before a
70: * pair of unequal elements is found, then the iterations are determined to
71: * be equal.
72: * <p>
73: * Neither iteration will be advanced past the point where an unequal pair
74: * is found, but the elements that were unequal will have been consumed.
75: *
76: * @return -1 if x < y, 1 if x > y, 0 if x == y
77: */
78: public int compare(Iterator<? extends T> x, Iterator<? extends T> y) {
79: while (true) {
80: if (x.hasNext()) {
81: if (y.hasNext()) {
82: int i = _comp.compare(x.next(), y.next());
83: if (i != 0) {
84: return i;
85: }
86: } else
87: return 1;
88: } else
89: return y.hasNext() ? -1 : 0;
90: }
91: }
92: }
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