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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
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());
Author: Helena Shih See Also: Since: 1.1
/**
* 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. Note:
CollationKeys created by different Collators can not be compared.
Params: - target – target CollationKey
See Also: Returns: 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.
/**
* 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.
Returns: the source string of this CollationKey
/**
* 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.
Returns: a byte array representation of the CollationKey
/**
* 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.
Params: - source – the source string
Throws: - NullPointerException – if
source is null
Since: 1.6
/**
* 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;
}