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CollationKey
abstract class CollationKey : Comparable<CollationKey!>
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.
<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 constructor.
|
| Public methods |
| abstract Int |
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. |
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 |
Content and code samples on this page are subject to the licenses described in the Content License. Java and OpenJDK are trademarks or registered trademarks of Oracle and/or its affiliates.
Last updated 2025-02-10 UTC.
[[["Easy to understand","easyToUnderstand","thumb-up"],["Solved my problem","solvedMyProblem","thumb-up"],["Other","otherUp","thumb-up"]],[["Missing the information I need","missingTheInformationINeed","thumb-down"],["Too complicated / too many steps","tooComplicatedTooManySteps","thumb-down"],["Out of date","outOfDate","thumb-down"],["Samples / code issue","samplesCodeIssue","thumb-down"],["Other","otherDown","thumb-down"]],["Last updated 2025-02-10 UTC."],[],[],null,["# CollationKey\n\nAdded in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels)\n\nCollationKey\n============\n\n```\nabstract class CollationKey : Comparable\u003cCollationKey!\u003e\n```\n\n|---|-----------------------------|\n| [kotlin.Any](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-any/index.html) ||\n| ↳ | [java.text.CollationKey](#) |\n\nA `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.\n\nYou 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.\n\nGenerating 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.\n\nThe following example shows how `CollationKey`s might be used to sort a list of `String`s. \n\n```kotlin\n\u003ccode\u003e// Create an array of CollationKeys for the Strings to be sorted.\n Collator myCollator = Collator.getInstance();\n CollationKey[] keys = new CollationKey[3];\n keys[0] = myCollator.getCollationKey(\"Tom\");\n keys[1] = myCollator.getCollationKey(\"Dick\");\n keys[2] = myCollator.getCollationKey(\"Harry\");\n sort(keys);\n \n //...\n \n // Inside body of sort routine, compare keys this way\n if (keys[i].compareTo(keys[j]) > 0)\n // swap keys[i] and keys[j]\n \n //...\n \n // Finally, when we've returned from sort.\n System.out.println(keys[0].getSourceString());\n System.out.println(keys[1].getSourceString());\n System.out.println(keys[2].getSourceString());\n \u003c/code\u003e\n```\n\nSummary\n-------\n\n| Protected constructors ||\n|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------|---|\n| [CollationKey](#CollationKey(kotlin.String))`(`source:` `[String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)!`)` CollationKey constructor. |\n\n| Public methods ||\n|---------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------|\n| abstract [Int](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html) | [compareTo](#compareTo(java.text.CollationKey))`(`other:` `[CollationKey](#)!`)` Compare this CollationKey to the target CollationKey. |\n| open [String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)! | [getSourceString](#getSourceString())`()` Returns the String that this CollationKey represents. |\n| abstract [ByteArray](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-byte-array/index.html)! | [toByteArray](#toByteArray())`()` Converts the CollationKey to a sequence of bits. |\n\nProtected constructors\n----------------------\n\n### CollationKey\n\nAdded in [API level 9](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) \n\n```\nprotected CollationKey(source: String!)\n```\n\nCollationKey constructor.\n\n| Parameters ||\n|----------|------------------------------------------------------------------------------------------------------|\n| `source` | [String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)!: the source string |\n\n| Exceptions ||\n|----------------------------------|---------------------|\n| `java.lang.NullPointerException` | if `source` is null |\n\nPublic methods\n--------------\n\n### compareTo\n\nAdded in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) \n\n```\nabstract fun compareTo(other: CollationKey!): Int\n```\n\nCompare 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.\n\n| Parameters ||\n|----------|----------------------------|\n| `o` | the object to be compared. |\n| `target` | target CollationKey |\n\n| Return ||\n|----------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|\n| [Int](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-int/index.html) | 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. |\n\n| Exceptions ||\n|----------------------------------|--------------------------------------------------------------------------------|\n| `java.lang.NullPointerException` | if the specified object is null |\n| `java.lang.ClassCastException` | if the specified object's type prevents it from being compared to this object. |\n\n**See Also**\n\n### getSourceString\n\nAdded in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) \n\n```\nopen fun getSourceString(): String!\n```\n\nReturns the String that this CollationKey represents.\n\n| Return ||\n|-----------------------------------------------------------------------------------|----------------------------------------|\n| [String](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-string/index.html)! | the source string of this CollationKey |\n\n### toByteArray\n\nAdded in [API level 1](https://developer.android.com/guide/topics/manifest/uses-sdk-element.html#ApiLevels) \n\n```\nabstract fun toByteArray(): ByteArray!\n```\n\nConverts 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.\n\n| Return ||\n|------------------------------------------------------------------------------------------|-------------------------------------------------|\n| [ByteArray](https://kotlinlang.org/api/latest/jvm/stdlib/kotlin/-byte-array/index.html)! | a byte array representation of the CollationKey |"]]
