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/*

 * (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</code> represents a <code>String</code> under the

 * rules of a specific <code>Collator</code> object. Comparing two

 * <code>CollationKey</code>s returns the relative order of the

 * <code>String</code>s they represent. Using <code>CollationKey</code>s

 * to compare <code>String</code>s is generally faster than using

 * <code>Collator.compare</code>. Thus, when the <code>String</code>s

 * must be compared multiple times, for example when sorting a list

 * of <code>String</code>s. It's more efficient to use <code>CollationKey</code>s.

 *

 * <p>

 * You can not create <code>CollationKey</code>s directly. Rather,

 * generate them by calling <code>Collator.getCollationKey</code>.

 * You can only compare <code>CollationKey</code>s generated from

 * the same <code>Collator</code> object.

 *

 * <p>

 * Generating a <code>CollationKey</code> for a <code>String</code>

 * involves examining the entire <code>String</code>

 * 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</code>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>.

 * <code>Collator.compare</code> 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</code>s might be used

 * to sort a list of <code>String</code>s.

 * <blockquote>

 * // 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");

 * //...

 * // Inside body of sort routine, compare keys this way

 *    // swap keys[i] and keys[j]

 * //...

 * // Finally, when we've returned from sort.

 * </blockquote>

 *

 * @see          Collator

 * @see          RuleBasedCollator

 * @author       Helena Shih

 */

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

     */

    abstract public int compareTo(CollationKey target);

    /**

     * Returns the String that this CollationKey represents.

     */

    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.

     */

    abstract public byte[] toByteArray();

  /**

   * CollationKey constructor.

   *

   * @since 1.6

   */

    protected CollationKey(String source) {

        if (source==null){

            throw new NullPointerException();

        }

        this.source = source;

    }

    final private String source;

}