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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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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>
 * <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
 * @exception 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;
}