396 lines
14 KiB
Java
396 lines
14 KiB
Java
/* Collator.java -- Perform locale dependent String comparisons.
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Copyright (C) 1998, 1999, 2000, 2001, 2004, 2005 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
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02110-1301 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.text;
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import gnu.java.locale.LocaleHelper;
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import java.util.Comparator;
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import java.util.Locale;
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import java.util.MissingResourceException;
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import java.util.ResourceBundle;
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/**
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* This class is the abstract superclass of classes which perform
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* locale dependent <code>String</code> comparisons. A caller requests
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* an instance of <code>Collator</code> for a particular locale using
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* the <code>getInstance()</code> static method in this class. That method
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* will return a locale specific subclass of <code>Collator</code> which
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* can be used to perform <code>String</code> comparisons for that locale.
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* If a subclass of <code>Collator</code> cannot be located for a particular
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* locale, a default instance for the current locale will be returned.
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*
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* In addition to setting the correct locale, there are two additional
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* settings that can be adjusted to affect <code>String</code> comparisons:
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* strength and decomposition. The strength value determines the level
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* of signficance of character differences required for them to sort
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* differently. (For example, whether or not capital letters are considered
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* different from lower case letters). The decomposition value affects how
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* variants of the same character are treated for sorting purposes. (For
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* example, whether or not an accent is signficant or not). These settings
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* are described in detail in the documentation for the methods and values
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* that are related to them.
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*
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* @author Tom Tromey (tromey@cygnus.com)
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* @author Aaron M. Renn (arenn@urbanophile.com)
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* @date March 18, 1999
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*/
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public abstract class Collator implements Comparator<Object>, Cloneable
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{
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/**
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* This constant is a strength value which indicates that only primary
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* differences between characters will be considered signficant. As an
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* example, two completely different English letters such as 'a' and 'b'
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* are considered to have a primary difference.
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*/
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public static final int PRIMARY = 0;
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/**
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* This constant is a strength value which indicates that only secondary
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* or primary differences between characters will be considered
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* significant. An example of a secondary difference between characters
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* are instances of the same letter with different accented forms.
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*/
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public static final int SECONDARY = 1;
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/**
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* This constant is a strength value which indicates that tertiary,
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* secondary, and primary differences will be considered during sorting.
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* An example of a tertiary difference is capitalization of a given letter.
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* This is the default value for the strength setting.
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*/
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public static final int TERTIARY = 2;
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/**
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* This constant is a strength value which indicates that any difference
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* at all between character values are considered significant.
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*/
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public static final int IDENTICAL = 3;
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/**
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* This constant indicates that accented characters won't be decomposed
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* when performing comparisons. This will yield the fastest results, but
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* will only work correctly in call cases for languages which do not
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* use accents such as English.
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*/
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public static final int NO_DECOMPOSITION = 0;
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/**
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* This constant indicates that only characters which are canonical variants
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* in Unicode 2.0 will be decomposed prior to performing comparisons. This
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* will cause accented languages to be sorted correctly. This is the
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* default decomposition value.
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*/
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public static final int CANONICAL_DECOMPOSITION = 1;
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/**
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* This constant indicates that both canonical variants and compatibility
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* variants in Unicode 2.0 will be decomposed prior to performing
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* comparisons. This is the slowest mode, but is required to get the
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* correct sorting for certain languages with certain special formats.
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*/
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public static final int FULL_DECOMPOSITION = 2;
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/**
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* This method initializes a new instance of <code>Collator</code> to have
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* the default strength (TERTIARY) and decomposition
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* (CANONICAL_DECOMPOSITION) settings. This constructor is protected and
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* is for use by subclasses only. Non-subclass callers should use the
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* static <code>getInstance()</code> methods of this class to instantiate
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* <code>Collation</code> objects for the desired locale.
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*/
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protected Collator ()
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{
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strength = TERTIARY;
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decmp = CANONICAL_DECOMPOSITION;
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}
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/**
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* This method compares the two <code>String</code>'s and returns an
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* integer indicating whether or not the first argument is less than,
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* equal to, or greater than the second argument. The comparison is
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* performed according to the rules of the locale for this
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* <code>Collator</code> and the strength and decomposition rules in
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* effect.
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*
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* @param source The first object to compare
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* @param target The second object to compare
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*
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* @return A negative integer if str1 < str2, 0 if str1 == str2, or
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* a positive integer if str1 > str2.
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*/
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public abstract int compare (String source, String target);
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/**
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* This method compares the two <code>Object</code>'s and returns an
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* integer indicating whether or not the first argument is less than,
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* equal to, or greater than the second argument. These two objects
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* must be <code>String</code>'s or an exception will be thrown.
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*
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* @param o1 The first object to compare
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* @param o2 The second object to compare
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*
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* @return A negative integer if obj1 < obj2, 0 if obj1 == obj2, or
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* a positive integer if obj1 > obj2.
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*
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* @exception ClassCastException If the arguments are not instances
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* of <code>String</code>.
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*/
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public int compare (Object o1, Object o2)
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{
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return compare ((String) o1, (String) o2);
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}
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/**
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* This method tests the specified object for equality against this
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* object. This will be true if and only if the following conditions are
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* met:
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* <ul>
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* <li>The specified object is not <code>null</code>.</li>
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* <li>The specified object is an instance of <code>Collator</code>.</li>
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* <li>The specified object has the same strength and decomposition
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* settings as this object.</li>
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* </ul>
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*
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* @param obj The <code>Object</code> to test for equality against
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* this object.
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*
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* @return <code>true</code> if the specified object is equal to
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* this one, <code>false</code> otherwise.
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*/
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public boolean equals (Object obj)
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{
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if (! (obj instanceof Collator))
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return false;
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Collator c = (Collator) obj;
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return decmp == c.decmp && strength == c.strength;
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}
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/**
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* This method tests whether the specified <code>String</code>'s are equal
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* according to the collation rules for the locale of this object and
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* the current strength and decomposition settings.
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*
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* @param source The first <code>String</code> to compare
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* @param target The second <code>String</code> to compare
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*
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* @return <code>true</code> if the two strings are equal,
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* <code>false</code> otherwise.
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*/
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public boolean equals (String source, String target)
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{
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return compare (source, target) == 0;
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}
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/**
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* This method returns a copy of this <code>Collator</code> object.
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*
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* @return A duplicate of this object.
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*/
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public Object clone ()
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{
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try
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{
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return super.clone ();
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}
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catch (CloneNotSupportedException _)
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{
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return null;
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}
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}
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/**
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* This method returns an array of <code>Locale</code> objects which is
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* the list of locales for which <code>Collator</code> objects exist.
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*
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* @return The list of locales for which <code>Collator</code>'s exist.
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*/
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public static synchronized Locale[] getAvailableLocales ()
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{
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return LocaleHelper.getCollatorLocales();
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}
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/**
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* This method transforms the specified <code>String</code> into a
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* <code>CollationKey</code> for faster comparisons. This is useful when
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* comparisons against a string might be performed multiple times, such
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* as during a sort operation.
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*
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* @param source The <code>String</code> to convert.
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*
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* @return A <code>CollationKey</code> for the specified <code>String</code>.
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*/
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public abstract CollationKey getCollationKey (String source);
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/**
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* This method returns the current decomposition setting for this
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* object. This * will be one of NO_DECOMPOSITION,
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* CANONICAL_DECOMPOSITION, or * FULL_DECOMPOSITION. See the
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* documentation for those constants for an * explanation of this
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* setting.
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*
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* @return The current decomposition setting.
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*/
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public synchronized int getDecomposition ()
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{
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return decmp;
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}
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/**
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* This method returns an instance of <code>Collator</code> for the
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* default locale.
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*
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* @return A <code>Collator</code> for the default locale.
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*/
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public static Collator getInstance ()
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{
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return getInstance (Locale.getDefault());
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}
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/**
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* This method returns an instance of <code>Collator</code> for the
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* specified locale. If no <code>Collator</code> exists for the desired
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* locale, a <code>Collator</code> for the default locale will be returned.
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*
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* @param loc The desired locale to load a <code>Collator</code> for.
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*
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* @return A <code>Collator</code> for the requested locale
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*/
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public static Collator getInstance (Locale loc)
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{
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ResourceBundle res;
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String pattern;
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try
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{
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res = ResourceBundle.getBundle("gnu.java.locale.LocaleInformation",
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loc, ClassLoader.getSystemClassLoader());
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pattern = res.getString("collation_rules");
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}
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catch (MissingResourceException x)
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{
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pattern = "<0<1<2<3<4<5<6<7<8<9<A,a<b,B<c,C<d,D<e,E<f,F<g,G<h,H<i,I<j,J<k,K" +
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"<l,L<m,M<n,N<o,O<p,P<q,Q<r,R<s,S<t,T<u,U<v,V<w,W<x,X<y,Y<z,Z";
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}
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try
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{
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return new RuleBasedCollator (pattern);
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}
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catch (ParseException x)
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{
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throw (InternalError)new InternalError().initCause(x);
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}
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}
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/**
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* This method returns the current strength setting for this object. This
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* will be one of PRIMARY, SECONDARY, TERTIARY, or IDENTICAL. See the
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* documentation for those constants for an explanation of this setting.
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*
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* @return The current strength setting.
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*/
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public synchronized int getStrength ()
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{
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return strength;
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}
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/**
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* This method returns a hash code value for this object.
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*
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* @return A hash value for this object.
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*/
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public abstract int hashCode ();
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/**
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* This method sets the decomposition setting for this object to the
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* specified value. This must be one of NO_DECOMPOSITION,
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* CANONICAL_DECOMPOSITION, or FULL_DECOMPOSITION. Otherwise an
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* exception will be thrown. See the documentation for those
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* contants for an explanation of this setting.
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*
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* @param mode The new decomposition setting.
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*
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* @exception IllegalArgumentException If the requested
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* decomposition setting is not valid.
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*/
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public synchronized void setDecomposition (int mode)
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{
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if (mode != NO_DECOMPOSITION
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&& mode != CANONICAL_DECOMPOSITION
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&& mode != FULL_DECOMPOSITION)
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throw new IllegalArgumentException ();
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decmp = mode;
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}
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/**
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* This method sets the strength setting for this object to the specified
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* value. This must be one of PRIMARY, SECONDARY, TERTIARY, or IDENTICAL.
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* Otherwise an exception is thrown. See the documentation for these
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* constants for an explanation of this setting.
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*
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* @param strength The new strength setting.
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*
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* @exception IllegalArgumentException If the requested strength
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* setting value is not valid.
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*/
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public synchronized void setStrength (int strength)
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{
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if (strength != PRIMARY && strength != SECONDARY
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&& strength != TERTIARY && strength != IDENTICAL)
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throw new IllegalArgumentException ();
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this.strength = strength;
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}
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// Decompose a single character and append results to the buffer.
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// FIXME: for libgcj this is a native method which handles
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// decomposition. For Classpath, for now, it does nothing.
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final void decomposeCharacter (char c, StringBuffer buf)
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{
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buf.append (c);
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}
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/**
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* This is the current collation decomposition setting.
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*/
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int decmp;
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/**
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* This is the current collation strength setting.
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*/
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int strength;
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}
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