/*
*
* @(#)CollationKey.java 1.21 06/10/10
*
* Portions Copyright 2000-2008 Sun Microsystems, Inc. All Rights
* Reserved. Use is subject to license terms.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
*
* This program 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.
*
* This program 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 at /legal/license.txt).
*
* 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 Sun Microsystems, Inc., 4150 Network Circle, Santa
* Clara, CA 95054 or visit www.sun.com if you need additional
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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>
* // 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 );
* <br>
* //...
* <br>
* // Inside body of sort routine, compare keys this way
* if( keys[i].compareTo( keys[j] ) > 0 )
* // swap keys[i] and keys[j]
* <br>
* //...
* <br>
* // 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
* @version 1.14, 01/19/00
* @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. <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 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;
}
/**
* Compares this CollationKey with the specified Object for order. Returns
* a negative integer, zero, or a positive integer as this CollationKey
* is less than, equal to, or greater than the given Object.
*
* @param o the Object to be compared.
* @return a negative integer, zero, or a positive integer as this
* Collation Key is less than, equal to, or greater than the given
* Object.
* @exception ClassCastException the specified Object is not a
* CollationKey.
* @see Comparable
* @since 1.2
*/
public int compareTo(Object o) {
return compareTo((CollationKey)o);
}
/**
* Compare this CollationKey and the target CollationKey for equality.
* 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 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<src.length; i++ ) {
dest[j++] = (byte)(src[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;
}