public abstract class CollationKey extends Object implements Comparable<CollationKey>
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.
// 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 string.NullPointerException
- if source
is null.public 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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For further API reference and developer documentation, see Java SE Documentation. That documentation contains more detailed, developer-targeted descriptions, with conceptual overviews, definitions of terms, workarounds, and working code examples.
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