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| 1 | /* | ||
| 2 | * Copyright (c) 1997, 2005, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | /* | ||
| 27 | * (C) Copyright Taligent, Inc. 1996 - All Rights Reserved | ||
| 28 | * (C) Copyright IBM Corp. 1996 - All Rights Reserved | ||
| 29 | * | ||
| 30 | * The original version of this source code and documentation is copyrighted | ||
| 31 | * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These | ||
| 32 | * materials are provided under terms of a License Agreement between Taligent | ||
| 33 | * and Sun. This technology is protected by multiple US and International | ||
| 34 | * patents. This notice and attribution to Taligent may not be removed. | ||
| 35 | * Taligent is a registered trademark of Taligent, Inc. | ||
| 36 | * | ||
| 37 | */ | ||
| 38 | |||
| 39 | package java.text; | ||
| 40 | |||
| 41 | /** | ||
| 42 | * A <code>CollationKey</code> represents a <code>String</code> under the | ||
| 43 | * rules of a specific <code>Collator</code> object. Comparing two | ||
| 44 | * <code>CollationKey</code>s returns the relative order of the | ||
| 45 | * <code>String</code>s they represent. Using <code>CollationKey</code>s | ||
| 46 | * to compare <code>String</code>s is generally faster than using | ||
| 47 | * <code>Collator.compare</code>. Thus, when the <code>String</code>s | ||
| 48 | * must be compared multiple times, for example when sorting a list | ||
| 49 | * of <code>String</code>s. It's more efficient to use <code>CollationKey</code>s. | ||
| 50 | * | ||
| 51 | * <p> | ||
| 52 | * You can not create <code>CollationKey</code>s directly. Rather, | ||
| 53 | * generate them by calling <code>Collator.getCollationKey</code>. | ||
| 54 | * You can only compare <code>CollationKey</code>s generated from | ||
| 55 | * the same <code>Collator</code> object. | ||
| 56 | * | ||
| 57 | * <p> | ||
| 58 | * Generating a <code>CollationKey</code> for a <code>String</code> | ||
| 59 | * involves examining the entire <code>String</code> | ||
| 60 | * and converting it to series of bits that can be compared bitwise. This | ||
| 61 | * allows fast comparisons once the keys are generated. The cost of generating | ||
| 62 | * keys is recouped in faster comparisons when <code>String</code>s need | ||
| 63 | * to be compared many times. On the other hand, the result of a comparison | ||
| 64 | * is often determined by the first couple of characters of each <code>String</code>. | ||
| 65 | * <code>Collator.compare</code> examines only as many characters as it needs which | ||
| 66 | * allows it to be faster when doing single comparisons. | ||
| 67 | * <p> | ||
| 68 | * The following example shows how <code>CollationKey</code>s might be used | ||
| 69 | * to sort a list of <code>String</code>s. | ||
| 70 | * <blockquote> | ||
| 71 | * <pre> | ||
| 72 | * // Create an array of CollationKeys for the Strings to be sorted. | ||
| 73 | * Collator myCollator = Collator.getInstance(); | ||
| 74 | * CollationKey[] keys = new CollationKey[3]; | ||
| 75 | * keys[0] = myCollator.getCollationKey("Tom"); | ||
| 76 | * keys[1] = myCollator.getCollationKey("Dick"); | ||
| 77 | * keys[2] = myCollator.getCollationKey("Harry"); | ||
| 78 | * sort( keys ); | ||
| 79 | * <br> | ||
| 80 | * //... | ||
| 81 | * <br> | ||
| 82 | * // Inside body of sort routine, compare keys this way | ||
| 83 | * if( keys[i].compareTo( keys[j] ) > 0 ) | ||
| 84 | * // swap keys[i] and keys[j] | ||
| 85 | * <br> | ||
| 86 | * //... | ||
| 87 | * <br> | ||
| 88 | * // Finally, when we've returned from sort. | ||
| 89 | * System.out.println( keys[0].getSourceString() ); | ||
| 90 | * System.out.println( keys[1].getSourceString() ); | ||
| 91 | * System.out.println( keys[2].getSourceString() ); | ||
| 92 | * </pre> | ||
| 93 | * </blockquote> | ||
| 94 | * | ||
| 95 | * @see Collator | ||
| 96 | * @see RuleBasedCollator | ||
| 97 | * @author Helena Shih | ||
| 98 | */ | ||
| 99 | |||
| 100 | public abstract class CollationKey implements Comparable<CollationKey> { | ||
| 101 | /** | ||
| 102 | * Compare this CollationKey to the target CollationKey. The collation rules of the | ||
| 103 | * Collator object which created these keys are applied. <strong>Note:</strong> | ||
| 104 | * CollationKeys created by different Collators can not be compared. | ||
| 105 | * @param target target CollationKey | ||
| 106 | * @return Returns an integer value. Value is less than zero if this is less | ||
| 107 | * than target, value is zero if this and target are equal and value is greater than | ||
| 108 | * zero if this is greater than target. | ||
| 109 | * @see java.text.Collator#compare | ||
| 110 | */ | ||
| 111 | abstract public int compareTo(CollationKey target); | ||
| 112 | |||
| 113 | /** | ||
| 114 | * Returns the String that this CollationKey represents. | ||
| 115 | */ | ||
| 116 | public String getSourceString() { | ||
| 117 | return source; | ||
| 118 | } | ||
| 119 | |||
| 120 | |||
| 121 | /** | ||
| 122 | * Converts the CollationKey to a sequence of bits. If two CollationKeys | ||
| 123 | * could be legitimately compared, then one could compare the byte arrays | ||
| 124 | * for each of those keys to obtain the same result. Byte arrays are | ||
| 125 | * organized most significant byte first. | ||
| 126 | */ | ||
| 127 | abstract public byte[] toByteArray(); | ||
| 128 | |||
| 129 | |||
| 130 | /** | ||
| 131 | * CollationKey constructor. | ||
| 132 | * | ||
| 133 | * @param source - the source string. | ||
| 134 | * @exception NullPointerException if <code>source</code> is null. | ||
| 135 | * @since 1.6 | ||
| 136 | */ | ||
| 137 | protected CollationKey(String source) { | ||
| 138 | if (source==null){ | ||
| 139 | throw new NullPointerException(); | ||
| 140 | } | ||
| 141 | this.source = source; | ||
| 142 | } | ||
| 143 | |||
| 144 | final private String source; | ||
| 145 | } | ||