public abstract class CollationKey extends Object implements Comparable<CollationKey>
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());
Collator,
RuleBasedCollator| Modifier | Constructor and Description |
|---|---|
protected |
CollationKey(String source)
CollationKey constructor.
|
| Modifier and Type | Method and Description |
|---|---|
abstract int |
compareTo(CollationKey target)
Compare this CollationKey to the target CollationKey.
|
String |
getSourceString()
Returns the String that this CollationKey represents.
|
abstract byte[] |
toByteArray()
Converts the CollationKey to a sequence of bits.
|
protected CollationKey(String source)
source - the source stringNullPointerException - if source is nullpublic abstract int compareTo(CollationKey target)
compareTo in interface Comparable<CollationKey>target - target CollationKeyCollator.compare(java.lang.String, java.lang.String)public String getSourceString()
public abstract byte[] toByteArray()
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