Source code: java/text/CollationKey.java
1 /* CollationKey.java -- Precomputed collation value
2 Copyright (C) 1998, 1999, 2000, 2003, 2005 Free Software Foundation, Inc.
3
4 This file is part of GNU Classpath.
5
6 GNU Classpath is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published by
8 the Free Software Foundation; either version 2, or (at your option)
9 any later version.
10
11 GNU Classpath is distributed in the hope that it will be useful, but
12 WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 General Public License for more details.
15
16 You should have received a copy of the GNU General Public License
17 along with GNU Classpath; see the file COPYING. If not, write to the
18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
19 02110-1301 USA.
20
21 Linking this library statically or dynamically with other modules is
22 making a combined work based on this library. Thus, the terms and
23 conditions of the GNU General Public License cover the whole
24 combination.
25
26 As a special exception, the copyright holders of this library give you
27 permission to link this library with independent modules to produce an
28 executable, regardless of the license terms of these independent
29 modules, and to copy and distribute the resulting executable under
30 terms of your choice, provided that you also meet, for each linked
31 independent module, the terms and conditions of the license of that
32 module. An independent module is a module which is not derived from
33 or based on this library. If you modify this library, you may extend
34 this exception to your version of the library, but you are not
35 obligated to do so. If you do not wish to do so, delete this
36 exception statement from your version. */
37
38
39 package java.text;
40
41 import java.util.Arrays;
42
43 /* Written using "Java Class Libraries", 2nd edition, plus online
44 * API docs for JDK 1.2 from http://www.javasoft.com.
45 * Status: Believed complete and correct.
46 */
47
48 /**
49 * This class represents a pre-computed series of bits representing a
50 * <code>String</code> for under a particular <code>Collator</code>. This
51 * value may be compared bitwise against another <code>CollationKey</code>
52 * representing a different <code>String</code> under the same
53 * <code>Collator</code> in a manner than is usually more efficient than
54 * using the raw <code>Collator</code> compare methods. There is overhead
55 * associated with calculating this value, so it is generally not
56 * advisable to compute <code>CollationKey</code>'s unless multiple
57 * comparisons against a <code>String</code> will be done. (For example,
58 * in a sort routine).
59 * <p>
60 * This class cannot be instantiated directly. Instead, a
61 * <code>CollationKey</code> is created by calling the
62 * <code>getCollationKey</code> method on an instance of <code>Collator</code>.
63 *
64 * @author Aaron M. Renn (arenn@urbanophile.com)
65 * @author Tom Tromey (tromey@cygnus.com)
66 * @date March 25, 1999
67 */
68 public final class CollationKey implements Comparable
69 {
70 /**
71 * This is the <code>Collator</code> this object was created from.
72 */
73 private Collator collator;
74
75 /**
76 * This is the <code>String</code> this object represents.
77 */
78 private String originalText;
79
80 /**
81 * This is the bit value for this key.
82 */
83 private byte[] key;
84
85 CollationKey (Collator collator, String originalText, byte[] key)
86 {
87 this.collator = collator;
88 this.originalText = originalText;
89 this.key = key;
90 }
91
92 /**
93 * This method compares the specified object to this one. An integer is
94 * returned which indicates whether the specified object is less than,
95 * greater than, or equal to this object.
96 *
97 * @param ck The <code>CollationKey</code> to compare against this one.
98 *
99 * @return A negative integer if this object is less than the specified object, 0 if it is equal or a positive integer if it is greater than the specified object.
100 */
101 public int compareTo (CollationKey ck)
102 {
103 int max = Math.min (key.length, ck.key.length);
104
105 for (int i = 0; i < max; ++i)
106 {
107 if (key[i] != ck.key[i])
108 return key[i] - ck.key[i];
109 }
110
111 return key.length - ck.key.length;
112 }
113
114 /**
115 * This method compares the specified object to this one. The specified
116 * object must be an instance of <code>CollationKey</code> or an exception
117 * will be thrown. An integer is returned which indicates whether the
118 * specified object is less than, greater than, or equal to this object.
119 *
120 * @param obj The <code>Object</code> to compare against this one.
121 *
122 * @return A negative integer if this object is less than the specified object, 0 if it is equal or a positive integer if it is greater than the specified object.
123 */
124 public int compareTo (Object obj)
125 {
126 return compareTo ((CollationKey) obj);
127 }
128
129 /**
130 * This method tests the specified <code>Object</code> for equality with
131 * this object. This will be true if and only if:
132 * <p>
133 * <ul>
134 * <li>The specified object must not be <code>null</code></li>
135 * <li>The specified object is an instance of <code>CollationKey</code>.</li>
136 * <li>The specified object was created from the same <code>Collator</code>
137 * as this object.</li>
138 * <li>The specified object has the same source string and bit key as
139 * this object.</li>
140 * </ul>
141 *
142 * @param obj The <code>Object</code> to test for equality.
143 *
144 * @return <code>true</code> if the specified object is equal to this one, <code>false</code> otherwise.
145 */
146 public boolean equals (Object obj)
147 {
148 if (! (obj instanceof CollationKey))
149 return false;
150
151 CollationKey ck = (CollationKey) obj;
152
153 if (ck.collator != collator)
154 return false;
155
156 if (!ck.getSourceString ().equals (getSourceString ()))
157 return false;
158
159 if (! Arrays.equals (ck.toByteArray (), toByteArray ()))
160 return false;
161
162 return true;
163 }
164
165 /**
166 * This method returns the <code>String</code> that this object was created
167 * from.
168 *
169 * @return The source <code>String</code> for this object.
170 */
171 public String getSourceString()
172 {
173 return originalText;
174 }
175
176 /**
177 * This method returns a hash value for this object. The hash value
178 * returned will be the hash code of the bit key so that identical bit
179 * keys will return the same value.
180 *
181 * @return A hash value for this object.
182 */
183 public int hashCode()
184 {
185 // We just follow BitSet instead of thinking up something new.
186 long h = originalText.hashCode();
187 for (int i = key.length - 1; i >= 0; --i)
188 h ^= key[i] * (i + 1);
189 return (int) ((h >> 32) ^ h);
190 }
191
192 /**
193 * This method returns the collation bit sequence as a byte array.
194 *
195 * @return A byte array containing the collation bit sequence.
196 */
197 public byte[] toByteArray()
198 {
199 return key;
200 }
201 }