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Added in API level 24

Collator

public abstract class Collator
extends Object implements Comparator<Object>, Freezable<Collator>, Cloneable

java.lang.Object
↳	android.icu.text.Collator

Known Direct Subclasses

RuleBasedCollator

[icu enhancement] ICU's replacement for Collator. Methods, fields, and other functionality specific to ICU are labeled '[icu]'.

Collator performs locale-sensitive string comparison. A concrete subclass, RuleBasedCollator, allows customization of the collation ordering by the use of rule sets.

A Collator is thread-safe only when frozen. See isFrozen() and Freezable.

Following the Unicode Consortium's specifications for the Unicode Collation Algorithm (UCA), there are 5 different levels of strength used in comparisons:

PRIMARY strength: Typically, this is used to denote differences between base characters (for example, "a" < "b"). It is the strongest difference. For example, dictionaries are divided into different sections by base character.
SECONDARY strength: Accents in the characters are considered secondary differences (for example, "as" < "às" < "at"). Other differences between letters can also be considered secondary differences, depending on the language. A secondary difference is ignored when there is a primary difference anywhere in the strings.
TERTIARY strength: Upper and lower case differences in characters are distinguished at tertiary strength (for example, "ao" < "Ao" < "aò"). In addition, a variant of a letter differs from the base form on the tertiary strength (such as "A" and "Ⓐ"). Another example is the difference between large and small Kana. A tertiary difference is ignored when there is a primary or secondary difference anywhere in the strings.
QUATERNARY strength: When punctuation is ignored (see Ignoring Punctuations in the User Guide) at PRIMARY to TERTIARY strength, an additional strength level can be used to distinguish words with and without punctuation (for example, "ab" < "a-b" < "aB"). This difference is ignored when there is a PRIMARY, SECONDARY or TERTIARY difference. The QUATERNARY strength should only be used if ignoring punctuation is required.
IDENTICAL strength: When all other strengths are equal, the IDENTICAL strength is used as a tiebreaker. The Unicode code point values of the NFD form of each string are compared, just in case there is no difference. For example, Hebrew cantellation marks are only distinguished at this strength. This strength should be used sparingly, as only code point value differences between two strings is an extremely rare occurrence. Using this strength substantially decreases the performance for both comparison and collation key generation APIs. This strength also increases the size of the collation key.

Unlike the JDK, ICU4J's Collator deals only with 2 decomposition modes, the canonical decomposition mode and one that does not use any decomposition. The compatibility decomposition mode, java.text.Collator.FULL_DECOMPOSITION is not supported here. If the canonical decomposition mode is set, the Collator handles un-normalized text properly, producing the same results as if the text were normalized in NFD. If canonical decomposition is turned off, it is the user's responsibility to ensure that all text is already in the appropriate form before performing a comparison or before getting a CollationKey.

For more information about the collation service see the User Guide.

Examples of use

 // 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");
 }

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

 // Compare two strings in the default locale
 Collator myCollator = Collator.getInstance();
 myCollator.setDecomposition(NO_DECOMPOSITION);
 if (myCollator.compare("à\u0325", "a\u0325̀") != 0) {
     System.out.println("à\u0325 is not equals to a\u0325̀ without decomposition");
     myCollator.setDecomposition(CANONICAL_DECOMPOSITION);
     if (myCollator.compare("à\u0325", "a\u0325̀") != 0) {
         System.out.println("Error: à\u0325 should be equals to a\u0325̀ with decomposition");
     }
     else {
         System.out.println("à\u0325 is equals to a\u0325̀ with decomposition");
     }
 }
 else {
     System.out.println("Error: à\u0325 should be not equals to a\u0325̀ without decomposition");
 }

See also:

Summary

Nested classes
`interface`	`Collator.ReorderCodes` Reordering codes for non-script groups that can be reordered under collation.

Constants
`int`	`CANONICAL_DECOMPOSITION` Decomposition mode value.
`int`	`FULL_DECOMPOSITION` [icu] Note: This is for backwards compatibility with Java APIs only.
`int`	`IDENTICAL` Smallest Collator strength value.
`int`	`NO_DECOMPOSITION` Decomposition mode value.
`int`	`PRIMARY` Strongest collator strength value.
`int`	`QUATERNARY` [icu] Fourth level collator strength value.
`int`	`SECONDARY` Second level collator strength value.
`int`	`TERTIARY` Third level collator strength value.

Protected constructors
`Collator()` Empty default constructor to make javadocs happy

Public methods
`Object`	`clone()` Clones the collator.
`Collator`	`cloneAsThawed()` Provides for the clone operation.
`int`	`compare(Object source, Object target)` Compares the source Object to the target Object.
`abstract int`	`compare(String source, String target)` Compares the source text String to the target text String according to this Collator's rules, strength and decomposition mode.
`boolean`	`equals(String source, String target)` Compares the equality of two text Strings using this Collator's rules, strength and decomposition mode.
`boolean`	`equals(Object obj)` Compares the equality of two Collator objects.
`Collator`	`freeze()` Freezes the collator.
`static Locale[]`	`getAvailableLocales()` Returns the set of locales, as Locale objects, for which collators are installed.
`static final ULocale[]`	`getAvailableULocales()` [icu] Returns the set of locales, as ULocale objects, for which collators are installed.
`abstract CollationKey`	`getCollationKey(String source)` Transforms the String into a CollationKey suitable for efficient repeated comparison.
`int`	`getDecomposition()` Returns the decomposition mode of this Collator.
`static String`	`getDisplayName(Locale objectLocale, Locale displayLocale)` [icu] Returns the name of the collator for the objectLocale, localized for the displayLocale.
`static String`	`getDisplayName(ULocale objectLocale)` [icu] Returns the name of the collator for the objectLocale, localized for the default `DISPLAY` locale.
`static String`	`getDisplayName(ULocale objectLocale, ULocale displayLocale)` [icu] Returns the name of the collator for the objectLocale, localized for the displayLocale.
`static String`	`getDisplayName(Locale objectLocale)` [icu] Returns the name of the collator for the objectLocale, localized for the default `DISPLAY` locale.
`static int[]`	`getEquivalentReorderCodes(int reorderCode)` Retrieves all the reorder codes that are grouped with the given reorder code.
`static final ULocale`	`getFunctionalEquivalent(String keyword, ULocale locID)` [icu] Returns the functionally equivalent locale for the given requested locale, with respect to given keyword, for the collation service.
`static final ULocale`	`getFunctionalEquivalent(String keyword, ULocale locID, boolean[] isAvailable)` [icu] Returns the functionally equivalent locale for the given requested locale, with respect to given keyword, for the collation service.
`static final Collator`	`getInstance()` Returns the Collator for the current default locale.
`static final Collator`	`getInstance(Locale locale)` Returns the Collator for the desired locale.
`static final Collator`	`getInstance(ULocale locale)` [icu] Returns the Collator for the desired locale.
`static final String[]`	`getKeywordValues(String keyword)` [icu] Given a keyword, returns an array of all values for that keyword that are currently in use.
`static final String[]`	`getKeywordValuesForLocale(String key, ULocale locale, boolean commonlyUsed)` [icu] Given a key and a locale, returns an array of string values in a preferred order that would make a difference.
`static final String[]`	`getKeywords()` [icu] Returns an array of all possible keywords that are relevant to collation.
`int`	`getMaxVariable()` [icu] Returns the maximum reordering group whose characters are affected by the alternate handling behavior.
`int[]`	`getReorderCodes()` Retrieves the reordering codes for this collator.
`int`	`getStrength()` Returns this Collator's strength attribute.
`UnicodeSet`	`getTailoredSet()` [icu] Returns a UnicodeSet that contains all the characters and sequences tailored in this collator.
`abstract VersionInfo`	`getUCAVersion()` [icu] Returns the UCA version of this collator object.
`abstract int`	`getVariableTop()` [icu] Gets the variable top value of a Collator.
`abstract VersionInfo`	`getVersion()` [icu] Returns the version of this collator object.
`boolean`	`isFrozen()` Determines whether the object has been frozen or not.
`void`	`setDecomposition(int decomposition)` Sets the decomposition mode of this Collator.
`Collator`	`setMaxVariable(int group)` [icu] Sets the variable top to the top of the specified reordering group.
`void`	`setReorderCodes(int... order)` Sets the reordering codes for this collator.
`void`	`setStrength(int newStrength)` Sets this Collator's strength attribute.

Inherited methods

From class


  
    java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long millis, int nanos)` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object, or some other thread interrupts the current thread, or a certain amount of real time has elapsed.
`final void`	`wait(long millis)` Causes the current thread to wait until either another thread invokes the `notify()` method or the `notifyAll()` method for this object, or a specified amount of time has elapsed.
`final void`	`wait()` Causes the current thread to wait until another thread invokes the `notify()` method or the `notifyAll()` method for this object.

From interface


  
    java.util.Comparator

`abstract int`	`compare(Object o1, Object o2)` Compares its two arguments for order.
`static <T, U> Comparator<Object>`	`comparing(Function<? super T, ? extends U> keyExtractor, Comparator<? super U> keyComparator)` Accepts a function that extracts a sort key from a type `T`, and returns a `Comparator<T>` that compares by that sort key using the specified `Comparator`.
`static <T, U extends Comparable<? super U>> Comparator<Object>`	`comparing(Function<? super T, ? extends U> keyExtractor)` Accepts a function that extracts a `Comparable` sort key from a type `T`, and returns a `Comparator<T>` that compares by that sort key.
`static <T> Comparator<Object>`	`comparingDouble(ToDoubleFunction<? super T> keyExtractor)` Accepts a function that extracts a `double` sort key from a type `T`, and returns a `Comparator<T>` that compares by that sort key.
`static <T> Comparator<Object>`	`comparingInt(ToIntFunction<? super T> keyExtractor)` Accepts a function that extracts an `int` sort key from a type `T`, and returns a `Comparator<T>` that compares by that sort key.
`static <T> Comparator<Object>`	`comparingLong(ToLongFunction<? super T> keyExtractor)` Accepts a function that extracts a `long` sort key from a type `T`, and returns a `Comparator<T>` that compares by that sort key.
`abstract boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this comparator.
`static <T extends Comparable<? super T>> Comparator<T>`	`naturalOrder()` Returns a comparator that compares `Comparable` objects in natural order.
`static <T> Comparator<Object>`	`nullsFirst(Comparator<? super T> comparator)` Returns a null-friendly comparator that considers `null` to be less than non-null.
`static <T> Comparator<Object>`	`nullsLast(Comparator<? super T> comparator)` Returns a null-friendly comparator that considers `null` to be greater than non-null.
`static <T extends Comparable<? super T>> Comparator<T>`	`reverseOrder()` Returns a comparator that imposes the reverse of the natural ordering.
`default Comparator<Object>`	`reversed()` Returns a comparator that imposes the reverse ordering of this comparator.
`default <U extends Comparable<? super U>> Comparator<Object>`	`thenComparing(Function<? super T, ? extends U> keyExtractor)` Returns a lexicographic-order comparator with a function that extracts a `Comparable` sort key.
`default <U> Comparator<Object>`	`thenComparing(Function<? super T, ? extends U> keyExtractor, Comparator<? super U> keyComparator)` Returns a lexicographic-order comparator with a function that extracts a key to be compared with the given `Comparator`.
`default Comparator<Object>`	`thenComparing(Comparator<? super T> other)` Returns a lexicographic-order comparator with another comparator.
`default Comparator<Object>`	`thenComparingDouble(ToDoubleFunction<? super T> keyExtractor)` Returns a lexicographic-order comparator with a function that extracts a `double` sort key.
`default Comparator<Object>`	`thenComparingInt(ToIntFunction<? super T> keyExtractor)` Returns a lexicographic-order comparator with a function that extracts a `int` sort key.
`default Comparator<Object>`	`thenComparingLong(ToLongFunction<? super T> keyExtractor)` Returns a lexicographic-order comparator with a function that extracts a `long` sort key.

From interface


  
    android.icu.util.Freezable

Constants

CANONICAL_DECOMPOSITION

Added in API level 24

int CANONICAL_DECOMPOSITION

Decomposition mode value. With CANONICAL_DECOMPOSITION set, characters that are canonical variants according to the Unicode standard will be decomposed for collation.

CANONICAL_DECOMPOSITION corresponds to Normalization Form D as described in Unicode Technical Report #15.

See also:

Constant Value: 17 (0x00000011)

FULL_DECOMPOSITION

Added in API level 24

int FULL_DECOMPOSITION

[icu] Note: This is for backwards compatibility with Java APIs only. It should not be used, IDENTICAL should be used instead. ICU's collation does not support Java's FULL_DECOMPOSITION mode.

Constant Value: 15 (0x0000000f)

IDENTICAL

Added in API level 24

int IDENTICAL

Smallest Collator strength value. When all other strengths are equal, the IDENTICAL strength is used as a tiebreaker. The Unicode code point values of the NFD form of each string are compared, just in case there is no difference. See class documentation for more explanation.

Note this value is different from JDK's

Constant Value: 15 (0x0000000f)

NO_DECOMPOSITION

Added in API level 24

int NO_DECOMPOSITION

Decomposition mode value. With NO_DECOMPOSITION set, Strings will not be decomposed for collation. This is the default decomposition setting unless otherwise specified by the locale used to create the Collator.

Note this value is different from the JDK's.

See also:

Constant Value: 16 (0x00000010)

PRIMARY

Added in API level 24

int PRIMARY

Strongest collator strength value. Typically used to denote differences between base characters. See class documentation for more explanation.

See also:

Constant Value: 0 (0x00000000)

QUATERNARY

Added in API level 24

int QUATERNARY

[icu] Fourth level collator strength value. When punctuation is ignored (see Ignoring Punctuation in the User Guide) at PRIMARY to TERTIARY strength, an additional strength level can be used to distinguish words with and without punctuation. See class documentation for more explanation.

See also:

Constant Value: 3 (0x00000003)

SECONDARY

Added in API level 24

int SECONDARY

Second level collator strength value. Accents in the characters are considered secondary differences. Other differences between letters can also be considered secondary differences, depending on the language. See class documentation for more explanation.

See also:

Constant Value: 1 (0x00000001)

TERTIARY

Added in API level 24

int TERTIARY

Third level collator strength value. Upper and lower case differences in characters are distinguished at this strength level. In addition, a variant of a letter differs from the base form on the tertiary level. See class documentation for more explanation.

See also:

Constant Value: 2 (0x00000002)

Parameters
`source`	`Object`: the source Object.
`target`	`Object`: the target Object.

Parameters
`source`	`String`: the source String.
`target`	`String`: the target String.

Parameters
`source`	`String`: the source string to be compared.
`target`	`String`: the target string to be compared.

Parameters
`objectLocale`	`Locale`: the locale of the collator
`displayLocale`	`Locale`: the locale for the collator's display name

Parameters
`objectLocale`	`ULocale`: the locale of the collator
`displayLocale`	`ULocale`: the locale for the collator's display name

Parameters
`keyword`	`String`: a particular keyword as enumerated by getKeywords.
`locID`	`ULocale`: The requested locale

Parameters
`key`	`String`: one of the keys supported by this service. For now, only "collation" is supported.
`locale`	`ULocale`: the locale
`commonlyUsed`	`boolean`: if set to true it will return only commonly used values with the given locale in preferred order. Otherwise, it will return all the available values for the locale.

Most visited

Recently visited

Results for

Collator

Summary

Nested classes

Constants

Protected constructors

Public methods

Inherited methods

Constants

CANONICAL_DECOMPOSITION

FULL_DECOMPOSITION

IDENTICAL

NO_DECOMPOSITION

PRIMARY

QUATERNARY

SECONDARY

TERTIARY

Protected constructors

Collator

Public methods

clone

cloneAsThawed

compare

compare

equals

equals

freeze

getAvailableLocales

getAvailableULocales

getCollationKey

getDecomposition

getDisplayName

getDisplayName

getDisplayName

getDisplayName

getEquivalentReorderCodes

getFunctionalEquivalent

getFunctionalEquivalent

getInstance

getInstance

getInstance

getKeywordValues

getKeywordValuesForLocale

getKeywords

getMaxVariable

getReorderCodes

getStrength

getTailoredSet

getUCAVersion

getVariableTop

getVersion

isFrozen

setDecomposition

setMaxVariable

setReorderCodes

setStrength