Added in API level 1

Collator

abstract class Collator : Comparator<Any!>, Cloneable
kotlin.Any
   ↳ java.text.Collator

The Collator class performs locale-sensitive String comparison. You use this class to build searching and sorting routines for natural language text.

Collator is an abstract base class. Subclasses implement specific collation strategies. One subclass, RuleBasedCollator, is currently provided with the Java Platform and is applicable to a wide set of languages. Other subclasses may be created to handle more specialized needs.

Like other locale-sensitive classes, you can use the static factory method, getInstance, to obtain the appropriate Collator object for a given locale. You will only need to look at the subclasses of Collator if you need to understand the details of a particular collation strategy or if you need to modify that strategy.

The following example shows how to compare two strings using the Collator for the default locale.

<code>// Compare two strings in the default locale
  Collator myCollator = Collator.getInstance();
  if( myCollator.compare("abc", "ABC") &lt; 0 )
      System.out.println("abc is less than ABC");
  else
      System.out.println("abc is greater than or equal to ABC");
  </code>

You can set a Collator's strength property to determine the level of difference considered significant in comparisons. Four strengths are provided: PRIMARY, SECONDARY, TERTIARY, and IDENTICAL. The exact assignment of strengths to language features is locale dependent. For example, in Czech, "e" and "f" are considered primary differences, while "e" and "ě" are secondary differences, "e" and "E" are tertiary differences and "e" and "e" are identical. The following shows how both case and accents could be ignored for US English.

//Get the Collator for US English and set its strength to PRIMARY
  Collator usCollator = Collator.getInstance(Locale.US);
  usCollator.setStrength(Collator.PRIMARY);
  if( usCollator.compare("abc", "ABC") == 0 ) {
      System.out.println("Strings are equivalent");
  }
  

For comparing Strings exactly once, the compare method provides the best performance. When sorting a list of Strings however, it is generally necessary to compare each String multiple times. In this case, CollationKeys provide better performance. The CollationKey class converts a String to a series of bits that can be compared bitwise against other CollationKeys. A CollationKey is created by a Collator object for a given String.
Note: CollationKeys from different Collators can not be compared. See the class description for CollationKey for an example using CollationKeys.

Summary

Constants
static Int

Decomposition mode value.

static Int

Decomposition mode value.

static Int

Collator strength value.

static Int

Decomposition mode value.

static Int

Collator strength value.

static Int

Collator strength value.

static Int

Collator strength value.

Protected constructors

Default constructor.

Public methods
open Any

Returns a new collator with the same decomposition mode and strength value as this collator.

abstract Int
compare(source: String!, target: String!)

Compares the source string to the target string according to the collation rules for this Collator.

open Int
compare(o1: Any!, o2: Any!)

Compares its two arguments for order.

open Boolean
equals(source: String!, target: String!)

Convenience method for comparing the equality of two strings based on this Collator's collation rules.

open Boolean
equals(other: Any?)

Compares the equality of two Collators.

open static Array<Locale!>!

Returns an array of all locales for which the getInstance methods of this class can return localized instances.

abstract CollationKey!

Transforms the String into a series of bits that can be compared bitwise to other CollationKeys.

open Int

Get the decomposition mode of this Collator.

open static Collator!

Gets the Collator for the current default locale.

open static Collator!
getInstance(desiredLocale: Locale!)

Gets the Collator for the desired locale.

open Int

Returns this Collator's strength property.

abstract Int

Generates the hash code for this Collator.

open Unit
setDecomposition(decompositionMode: Int)

Set the decomposition mode of this Collator.

open Unit
setStrength(newStrength: Int)

Sets this Collator's strength property.

Inherited functions

Constants

CANONICAL_DECOMPOSITION

Added in API level 1
static val CANONICAL_DECOMPOSITION: Int

Decomposition mode value. With CANONICAL_DECOMPOSITION set, characters that are canonical variants according to Unicode standard will be decomposed for collation. This should be used to get correct collation of accented characters.

CANONICAL_DECOMPOSITION corresponds to Normalization Form D as described in Unicode Standard Annex #15: Unicode Normalization Forms.

Value: 1

FULL_DECOMPOSITION

Added in API level 1
static val FULL_DECOMPOSITION: Int

Decomposition mode value. With FULL_DECOMPOSITION set, both Unicode canonical variants and Unicode compatibility variants will be decomposed for collation. This causes not only accented characters to be collated, but also characters that have special formats to be collated with their norminal form. For example, the half-width and full-width ASCII and Katakana characters are then collated together. FULL_DECOMPOSITION is the most complete and therefore the slowest decomposition mode.

FULL_DECOMPOSITION corresponds to Normalization Form KD as described in Unicode Standard Annex #15: Unicode Normalization Forms.

Value: 2

IDENTICAL

Added in API level 1
static val IDENTICAL: Int

Collator strength value. When set, all differences are considered significant during comparison. The assignment of strengths to language features is locale dependent. A common example is for control characters ("\u0001" vs "\u0002") to be considered equal at the PRIMARY, SECONDARY, and TERTIARY levels but different at the IDENTICAL level. Additionally, differences between pre-composed accents such as "\u00C0" (A-grave) and combining accents such as "A\u0300" (A, combining-grave) will be considered significant at the IDENTICAL level if decomposition is set to NO_DECOMPOSITION.

Value: 3

NO_DECOMPOSITION

Added in API level 1
static val NO_DECOMPOSITION: Int

Decomposition mode value. With NO_DECOMPOSITION set, accented characters will not be decomposed for collation. This is the default setting and provides the fastest collation but will only produce correct results for languages that do not use accents.

Value: 0

PRIMARY

Added in API level 1
static val PRIMARY: Int

Collator strength value. When set, only PRIMARY differences are considered significant during comparison. The assignment of strengths to language features is locale dependent. A common example is for different base letters ("a" vs "b") to be considered a PRIMARY difference.

Value: 0

SECONDARY

Added in API level 1
static val SECONDARY: Int

Collator strength value. When set, only SECONDARY and above differences are considered significant during comparison. The assignment of strengths to language features is locale dependent. A common example is for different accented forms of the same base letter ("a" vs "\u00E4") to be considered a SECONDARY difference.

Value: 1

TERTIARY

Added in API level 1
static val TERTIARY: Int

Collator strength value. When set, only TERTIARY and above differences are considered significant during comparison. The assignment of strengths to language features is locale dependent. A common example is for case differences ("a" vs "A") to be considered a TERTIARY difference.

Value: 2

Protected constructors

Collator

Added in API level 1
protected Collator()

Default constructor. This constructor is protected so subclasses can get access to it. Users typically create a Collator sub-class by calling the factory method getInstance.

See Also

    Public methods

    clone

    Added in API level 1
    open fun clone(): Any

    Returns a new collator with the same decomposition mode and strength value as this collator.

    Return
    Any a shallow copy of this collator.
    Exceptions
    java.lang.CloneNotSupportedException if the object's class does not support the Cloneable interface. Subclasses that override the clone method can also throw this exception to indicate that an instance cannot be cloned.

    compare

    Added in API level 1
    abstract fun compare(
        source: String!,
        target: String!
    ): Int

    Compares the source string to the target string according to the collation rules for this Collator. Returns an integer less than, equal to or greater than zero depending on whether the source String is less than, equal to or greater than the target string. See the Collator class description for an example of use.

    For a one time comparison, this method has the best performance. If a given String will be involved in multiple comparisons, CollationKey.compareTo has the best performance. See the Collator class description for an example using CollationKeys.

    Parameters
    source String!: the source string.
    target String!: the target string.
    Return
    Int Returns an integer value. Value is less than zero if source is less than target, value is zero if source and target are equal, value is greater than zero if source is greater than target.

    compare

    Added in API level 1
    open fun compare(
        o1: Any!,
        o2: Any!
    ): Int

    Compares its two arguments for order. Returns a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.

    This implementation merely returns compare((String)o1, (String)o2) .

    Parameters
    o1 Any!: the first object to be compared.
    o2 Any!: the second object to be compared.
    Return
    Int a negative integer, zero, or a positive integer as the first argument is less than, equal to, or greater than the second.
    Exceptions
    java.lang.NullPointerException if an argument is null and this comparator does not permit null arguments
    java.lang.ClassCastException the arguments cannot be cast to Strings.

    equals

    Added in API level 1
    open fun equals(
        source: String!,
        target: String!
    ): Boolean

    Convenience method for comparing the equality of two strings based on this Collator's collation rules.

    Parameters
    source String!: the source string to be compared with.
    target String!: the target string to be compared with.
    Return
    Boolean true if the strings are equal according to the collation rules. false, otherwise.

    See Also

      equals

      Added in API level 1
      open fun equals(other: Any?): Boolean

      Compares the equality of two Collators.

      Parameters
      obj the reference object with which to compare.
      that the Collator to be compared with this.
      Return
      Boolean true if this Collator is the same as that Collator; false otherwise.

      getAvailableLocales

      Added in API level 1
      open static fun getAvailableLocales(): Array<Locale!>!

      Returns an array of all locales for which the getInstance methods of this class can return localized instances.

      Return
      Array<Locale!>! An array of locales for which localized Collator instances are available.

      getCollationKey

      Added in API level 1
      abstract fun getCollationKey(source: String!): CollationKey!

      Transforms the String into a series of bits that can be compared bitwise to other CollationKeys. CollationKeys provide better performance than Collator.compare when Strings are involved in multiple comparisons. See the Collator class description for an example using CollationKeys.

      Parameters
      source String!: the string to be transformed into a collation key.
      Return
      CollationKey! the CollationKey for the given String based on this Collator's collation rules. If the source String is null, a null CollationKey is returned.

      getDecomposition

      Added in API level 1
      open fun getDecomposition(): Int

      Get the decomposition mode of this Collator. Decomposition mode determines how Unicode composed characters are handled. Adjusting decomposition mode allows the user to select between faster and more complete collation behavior.

      The three values for decomposition mode are:

      • NO_DECOMPOSITION,
      • CANONICAL_DECOMPOSITION
      • FULL_DECOMPOSITION.
      See the documentation for these three constants for a description of their meaning.
      Return
      Int the decomposition mode

      getInstance

      Added in API level 1
      open static fun getInstance(): Collator!

      Gets the Collator for the current default locale. The default locale is determined by java.util.Locale.getDefault.

      Return
      Collator! the Collator for the default locale.(for example, en_US)

      See Also

        getInstance

        Added in API level 1
        open static fun getInstance(desiredLocale: Locale!): Collator!

        Gets the Collator for the desired locale.

        Parameters
        desiredLocale Locale!: the desired locale.
        Return
        Collator! the Collator for the desired locale.

        getStrength

        Added in API level 1
        open fun getStrength(): Int

        Returns this Collator's strength property. The strength property determines the minimum level of difference considered significant during comparison. See the Collator class description for an example of use.

        Return
        Int this Collator's current strength property.

        hashCode

        Added in API level 1
        abstract fun hashCode(): Int

        Generates the hash code for this Collator.

        Return
        Int a hash code value for this object.

        setDecomposition

        Added in API level 1
        open fun setDecomposition(decompositionMode: Int): Unit

        Set the decomposition mode of this Collator. See getDecomposition for a description of decomposition mode.

        Parameters
        decompositionMode Int: the new decomposition mode.
        Exceptions
        java.lang.IllegalArgumentException If the given value is not a valid decomposition mode.

        setStrength

        Added in API level 1
        open fun setStrength(newStrength: Int): Unit

        Sets this Collator's strength property. The strength property determines the minimum level of difference considered significant during comparison. See the Collator class description for an example of use.

        Parameters
        newStrength Int: the new strength value.
        Exceptions
        java.lang.IllegalArgumentException If the new strength value is not one of PRIMARY, SECONDARY, TERTIARY or IDENTICAL.