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/*
* Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* (C) Copyright Taligent, Inc. 1996 - All Rights Reserved
* (C) Copyright IBM Corp. 1996 - 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.
*
*/
package java.text;
/**
* A {@code CollationKey} represents a {@code String} under the
* rules of a specific {@code Collator} object. Comparing two
* {@code CollationKey}s returns the relative order of the
* {@code String}s they represent. Using {@code CollationKey}s
* to compare {@code String}s is generally faster than using
* {@code Collator.compare}. Thus, when the {@code String}s
* must be compared multiple times, for example when sorting a list
* of {@code String}s. It's more efficient to use {@code CollationKey}s.
*
* <p>
* You can not create {@code CollationKey}s directly. Rather,
* generate them by calling {@code Collator.getCollationKey}.
* You can only compare {@code CollationKey}s generated from
* the same {@code Collator} object.
*
* <p>
* Generating a {@code CollationKey} for a {@code String}
* involves examining the entire {@code String}
* and converting it to series of bits that can be compared bitwise. This
* allows fast comparisons once the keys are generated. The cost of generating
* keys is recouped in faster comparisons when {@code String}s need
* to be compared many times. On the other hand, the result of a comparison
* is often determined by the first couple of characters of each {@code String}.
* {@code Collator.compare} examines only as many characters as it needs which
* allows it to be faster when doing single comparisons.
* <p>
* The following example shows how {@code CollationKey}s might be used
* to sort a list of {@code String}s.
* <blockquote>
* {@snippet lang=java :
* // Create an array of CollationKeys for the Strings to be sorted.
* Collator myCollator = Collator.getInstance();
* CollationKey[] keys = new CollationKey[3];
* keys[0] = myCollator.getCollationKey("Tom");
* keys[1] = myCollator.getCollationKey("Dick");
* keys[2] = myCollator.getCollationKey("Harry");
* sort(keys);
*
* //...
*
* // Inside body of sort routine, compare keys this way
* if (keys[i].compareTo(keys[j]) > 0)
* // swap keys[i] and keys[j]
*
* //...
*
* // Finally, when we've returned from sort.
* System.out.println(keys[0].getSourceString());
* System.out.println(keys[1].getSourceString());
* System.out.println(keys[2].getSourceString());
* }
* </blockquote>
*
* @see Collator
* @see RuleBasedCollator
* @author Helena Shih
* @since 1.1
*/
public abstract class CollationKey implements Comparable<CollationKey> {
/**
* Compare this CollationKey to the target CollationKey. The collation rules of the
* Collator object which created these keys are applied. <strong>Note:</strong>
* CollationKeys created by different Collators can not be compared.
* @param target target CollationKey
* @return Returns an integer value. Value is less than zero if this is less
* than target, value is zero if this and target are equal and value is greater than
* zero if this is greater than target.
* @see java.text.Collator#compare
*/
public abstract int compareTo(CollationKey target);
/**
* Returns the String that this CollationKey represents.
*
* @return the source string of this CollationKey
*/
public String getSourceString() {
return source;
}
/**
* Converts the CollationKey to a sequence of bits. If two CollationKeys
* could be legitimately compared, then one could compare the byte arrays
* for each of those keys to obtain the same result. Byte arrays are
* organized most significant byte first.
*
* @return a byte array representation of the CollationKey
*/
public abstract byte[] toByteArray();
/**
* CollationKey constructor.
*
* @param source the source string
* @throws NullPointerException if {@code source} is null
* @since 1.6
*/
protected CollationKey(String source) {
if (source==null){
throw new NullPointerException();
}
this.source = source;
}
private final String source;
}