/*
* @(#)CollationKey.java 1.18 04/05/05
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
/*
* (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
* CollationKeys returns the relative order of the
* Strings they represent. Using CollationKeys
* to compare Strings is generally faster than using
* Collator.compare. Thus, when the Strings
* must be compared multiple times, for example when sorting a list
* of Strings. It's more efficient to use CollationKeys.
*
*
* You can not create CollationKeys directly. Rather,
* generate them by calling Collator.getCollationKey.
* You can only compare CollationKeys 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 Strings 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 CollationKeys might be used
* to sort a list of Strings.
*
*
* // 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
* @version 1.18, 05/05/04
* @author Helena Shih
*/
public final 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
*/
public int compareTo(CollationKey target)
{
int result = key.compareTo(target.key);
if (result <= Collator.LESS)
return Collator.LESS;
else if (result >= Collator.GREATER)
return Collator.GREATER;
return Collator.EQUAL;
}
/**
* Compare this CollationKey and the target CollationKey for equality.
* 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 the CollationKey to compare to.
* @return Returns true if two objects are equal, false otherwise.
*/
public boolean equals(Object target) {
if (this == target) return true;
if (target == null || !getClass().equals(target.getClass())) {
return false;
}
CollationKey other = (CollationKey)target;
return key.equals(other.key);
}
/**
* Creates a hash code for this CollationKey. The hash value is calculated on the
* key itself, not the String from which the key was created. Thus
* if x and y are CollationKeys, then x.hashCode(x) == y.hashCode() if
* x.equals(y) is true. This allows language-sensitive comparison in a hash table.
* See the CollatinKey class description for an example.
* @return the hash value based on the string's collation order.
*/
public int hashCode() {
return (key.hashCode());
}
/**
* 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.
*/
public byte[] toByteArray() {
char[] src = key.toCharArray();
byte[] dest = new byte[ 2*src.length ];
int j = 0;
for( int i=0; i>> 8);
dest[j++] = (byte)(src[i] & 0x00ff);
}
return dest;
}
/**
* A CollationKey can only be generated by Collator objects.
*/
CollationKey(String source, String key) {
this.source = source;
this.key = key;
}
private String source = null;
private String key = null;
}