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/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* accompanied this code).
*
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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 CollationKey
represents a String
under the
* rules of a specific Collator
object. Comparing two
* CollationKey
s returns the relative order of the
* String
s they represent. Using CollationKey
s
* to compare String
s is generally faster than using
* Collator.compare
. Thus, when the String
s
* must be compared multiple times, for example when sorting a list
* of String
s. It's more efficient to use CollationKey
s.
*
*
* You can not create CollationKey
s directly. Rather,
* generate them by calling Collator.getCollationKey
.
* You can only compare CollationKey
s generated from
* the same Collator
object.
*
*
* Generating a CollationKey
for a String
* involves examining the entire 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 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 String
.
* Collator.compare
examines only as many characters as it needs which
* allows it to be faster when doing single comparisons.
*
* The following example shows how CollationKey
s might be used
* to sort a list of String
s.
*
* {@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());
* }
*
*
* @see Collator
* @see RuleBasedCollator
* @author Helena Shih
*/
public abstract class CollationKey implements Comparable {
/**
* Compare this CollationKey to the target CollationKey. The collation rules of the
* Collator object which created these keys are applied. Note:
* 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.
*
* @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
*/
abstract public 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;
}
final private String source;
}