rulebasedcollator.java

来自「《移动Agent技术》一书的所有章节源代码。」· Java 代码 · 共 115 行

/*
 * @(#)RuleBasedCollator.java	1.21 98/02/12
 *
 * (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
 * (C) Copyright IBM Corp. 1996, 1997 - All Rights Reserved
 *
 * Portions copyright (c) 1996 Sun Microsystems, Inc. All Rights Reserved.
 *
 *   The original version of this source code and documentation is copyrighted
 * and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
 * materials are provided under terms of a License Agreement between Taligent
 * and Sun. This technology is protected by multiple US and International
 * patents. This notice and attribution to Taligent may not be removed.
 *   Taligent is a registered trademark of Taligent, Inc.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies. Please refer to the file "copyright.html"
 * for further important copyright and licensing information.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
 * TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
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 *
 */

package java.text;

import java.util.Vector;
import java.io.ObjectOutputStream;
import java.io.ObjectInputStream;
import java.io.IOException;

/**
 * The <code>RuleBasedCollator</code> class is a concrete subclass of
 * <code>Collator</code> that provides a simple, data-driven, table collator.
 * With this class you can create a customized table-based <code>Collator</code>.
 * <code>RuleBasedCollator</code> maps characters to sort keys.
 *
 * <p>
 * <code>RuleBasedCollator</code> has the following restrictions
 * for efficiency (other subclasses may be used for more complex languages) :
 * <ol>
 * <li>If a French secondary ordering is specified it applies to the
 *     whole collator object.
 * <li>All non-mentioned Unicode characters are at the end of the
 *     collation order.
 * <li>Private use characters are treated as identical.  The private
 *     use area in Unicode is <code>0xE800</code>-<code>0xF8FF</code>.
 * </ol>
 *
 * <p>
 * The collation table is composed of a list of collation rules, where each
 * rule is of three forms:
 * <pre>
 *    < modifier >
 *    < relation > < text-argument >
 *    < reset > < text-argument >
 * </pre>
 * The following demonstrates how to create your own collation rules:
 * <UL Type=round>
 *    <LI><strong>Text-Argument</strong>: A text-argument is any sequence of
 *        characters, excluding special characters (that is, whitespace
 *        characters and the characters used in modifier, relation and reset).
 *        If those characters are desired, you can put them in single quotes
 *        (e.g. ampersand => '&').  Note that unquoted white space characters
 *        are ignored; e.g. <code>b c</code> is treated as <code>bc</code>.
 *    <LI><strong>Modifier</strong>: There is a single modifier
 *        which is used to specify that all accents (secondary differences) are
 *        backwards.
 *        <p>'@' : Indicates that accents are sorted backwards, as in French.
 *    <LI><strong>Relation</strong>: The relations are the following:
 *        <UL Type=square>
 *            <LI>'<' : Greater, as a letter difference (primary)
 *            <LI>';' : Greater, as an accent difference (secondary)
 *            <LI>',' : Greater, as a case difference (tertiary)
 *            <LI>'=' : Equal
 *        </UL>
 *    <LI><strong>Reset</strong>: There is a single reset
 *        which is used primarily for contractions and expansions, but which
 *        can also be used to add a modification at the end of a set of rules.
 *        <p>'&' : Indicates that the next rule follows the position to where
 *            the reset text-argument would be sorted.
 * </UL>
 *
 * <p>
 * This sounds more complicated than it is in practice. For example, the
 * following are equivalent ways of expressing the same thing:
 * <blockquote>
 * <pre>
 * a < b < c
 * a < b & b < c
 * a < c & a < b
 * </pre>
 * </blockquote>
 * Notice that the order is important, as the subsequent item goes immediately
 * after the text-argument. The following are not equivalent:
 * <blockquote>
 * <pre>
 * a < b & a < c
 * a < c & a < b
 * </pre>
 * </blockquote>
 * Either the text-argument must already be present in the sequence, or some
 * initial substring of the text-argument must be present. (e.g. "a < b & ae <
 * e" is valid since "a" is present in the sequence before "ae" is reset). In
 * this latter case, "ae" is not entered and treated as a single character;
 * instead, "e" is sorted as if it were expanded to two characters: "a"
 * followed by an "e". This difference appears in natural languages: in
 * traditional Spanish "ch" is treated as though it contracts to a single
 * character (expressed as "c < ch < d"), while in traditional German "