/*

 * Copyright (c) 1997, 2019, 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>

 * <pre>{@code

 * // 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());

 * }</pre>

 * </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;

}