CollationKey
abstract class CollationKey : Comparable<CollationKey!>
kotlin.Any | |
↳ | java.text.CollationKey |
A 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.
<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()); </code>
Summary
Protected constructors | |
---|---|
CollationKey(source: String!) CollationKey constructor. |
Public methods | |
---|---|
abstract Int |
compareTo(other: CollationKey!) Compare this CollationKey to the target CollationKey. |
open String! |
Returns the String that this CollationKey represents. |
abstract ByteArray! |
Converts the CollationKey to a sequence of bits. |
Protected constructors
CollationKey
protected CollationKey(source: String!)
CollationKey constructor.
Parameters | |
---|---|
source |
String!: the source string |
Exceptions | |
---|---|
java.lang.NullPointerException |
if source is null |
Public methods
compareTo
abstract fun compareTo(other: CollationKey!): Int
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.
Parameters | |
---|---|
o |
the object to be compared. |
target |
target CollationKey |
Return | |
---|---|
Int |
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. |
Exceptions | |
---|---|
java.lang.NullPointerException |
if the specified object is null |
java.lang.ClassCastException |
if the specified object's type prevents it from being compared to this object. |
See Also
getSourceString
open fun getSourceString(): String!
Returns the String that this CollationKey represents.
Return | |
---|---|
String! |
the source string of this CollationKey |
toByteArray
abstract fun toByteArray(): ByteArray!
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 | |
---|---|
ByteArray! |
a byte array representation of the CollationKey |