001: /* ====================================================================
002: * The QueryForm License, Version 1.1
003: *
004: * Copyright (c) 1998 - 2003 David F. Glasser. All rights
005: * reserved.
006: *
007: * Redistribution and use in source and binary forms, with or without
008: * modification, are permitted provided that the following conditions
009: * are met:
010: *
011: * 1. Redistributions of source code must retain the above copyright
012: * notice, this list of conditions and the following disclaimer.
013: *
014: * 2. Redistributions in binary form must reproduce the above copyright
015: * notice, this list of conditions and the following disclaimer in
016: * the documentation and/or other materials provided with the
017: * distribution.
018: *
019: * 3. The end-user documentation included with the redistribution,
020: * if any, must include the following acknowledgment:
021: * "This product includes software developed by
022: * David F. Glasser."
023: * Alternately, this acknowledgment may appear in the software itself,
024: * if and wherever such third-party acknowledgments normally appear.
025: *
026: * 4. The names "QueryForm" and "David F. Glasser" must
027: * not be used to endorse or promote products derived from this
028: * software without prior written permission. For written
029: * permission, please contact dglasser@pobox.com.
030: *
031: * 5. Products derived from this software may not be called "QueryForm",
032: * nor may "QueryForm" appear in their name, without prior written
033: * permission of David F. Glasser.
034: *
035: * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
036: * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
037: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
038: * DISCLAIMED. IN NO EVENT SHALL DAVID F. GLASSER, THE APACHE SOFTWARE
039: * FOUNDATION OR ITS CONTRIBUTORS, OR ANY AUTHORS OR DISTRIBUTORS
040: * OF THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
041: * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
042: * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
043: * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
044: * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
045: * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
046: * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
047: * SUCH DAMAGE.
048: * ====================================================================
049: *
050: * This product includes software developed by the
051: * Apache Software Foundation (http://www.apache.org/).
052: *
053: * ====================================================================
054: *
055: * $Source: /cvsroot/qform/qform/src/org/glasser/util/comparators/MapComparator.java,v $
056: * $Revision: 1.1 $
057: * $Author: dglasser $
058: * $Date: 2003/01/25 18:08:20 $
059: *
060: * --------------------------------------------------------------------
061: */
062: package org.glasser.util.comparators;
063:
064: import java.util.*;
065:
066: /**
067: * This Comparator is used for sorting a collection of Maps. An instance
068: * is given a "key" object when it's constructed. Each time it is given
069: * two Maps to compare, it will use the key to get a value from each map,
070: * and compare those two values to determine the ordering of the two
071: * maps.
072: * <p>
073: * If a separate "value comparator" is provided, it will be used to compare
074: * the values fetched from the Maps. Otherwise, if the fetched values are
075: * java.util.Comparables, they'll be compared with the compareTo() method
076: * of the first value. Finally, if no value comparator was provided and the fetched
077: * values are not Comparables, their toString() values will be compared.
078: */
079: public class MapComparator extends BaseComparator {
080:
081: private Object key = null;
082:
083: private Comparator valueComparator = null;
084:
085: public MapComparator(Object key) {
086: this .key = key;
087: }
088:
089: public MapComparator(Object key, Comparator valueComparator) {
090: this .key = key;
091: this .valueComparator = valueComparator;
092: }
093:
094: public MapComparator(Object key, Comparator valueComparator,
095: boolean nullIsGreater, boolean sortDescending,
096: Comparator nestedComparator) {
097: super (nullIsGreater, sortDescending, nestedComparator);
098: this .key = key;
099: this .valueComparator = valueComparator;
100: }
101:
102: public int doCompare(Object o1, Object o2) {
103:
104: Object val1 = ((Map) o1).get(key);
105: Object val2 = ((Map) o2).get(key);
106:
107: if (val1 == null && val2 == null)
108: return 0;
109:
110: int retVal = super .compareForNulls(val1, val2);
111:
112: if (retVal != 0)
113: return retVal;
114:
115: // both values are non-null
116: if (valueComparator != null)
117: return valueComparator.compare(val1, val2);
118:
119: if (val1 instanceof Comparable)
120: return ((Comparable) val1).compareTo((Comparable) val2);
121:
122: return val1.toString().compareTo(val2.toString());
123:
124: }
125:
126: }
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