com.ibm.icu.text
public final class RuleBasedCollator extends Collator
RuleBasedCollator is a concrete subclass of Collator. It allows customization of the Collator via user-specified rule sets. RuleBasedCollator is designed to be fully compliant to the Unicode Collation Algorithm (UCA) and conforms to ISO 14651.
Users are strongly encouraged to read the users guide for more information about the collation service before using this class.
Create a RuleBasedCollator from a locale by calling the getInstance(Locale) factory method in the base class Collator. Collator.getInstance(Locale) creates a RuleBasedCollator object based on the collation rules defined by the argument locale. If a customized collation ordering ar attributes is required, use the RuleBasedCollator(String) constructor with the appropriate rules. The customized RuleBasedCollator will base its ordering on UCA, while re-adjusting the attributes and orders of the characters in the specified rule accordingly.
RuleBasedCollator provides correct collation orders for most locales supported in ICU. If specific data for a locale is not available, the orders eventually falls back to the UCA collation order .
For information about the collation rule syntax and details about customization, please refer to the Collation customization section of the user's guide.
Note that there are some differences between the Collation rule syntax used in Java and ICU4J:
Modifier '!' : Turns on Thai/Lao vowel-consonant swapping. If this rule is in force when a Thai vowel of the range \U0E40-\U0E44 precedes a Thai consonant of the range \U0E01-\U0E2E OR a Lao vowel of the range \U0EC0-\U0EC4 precedes a Lao consonant of the range \U0E81-\U0EAE then the vowel is placed after the consonant for collation purposes.
If a rule is without the modifier '!', the Thai/Lao vowel-consonant swapping is not turned on.
ICU4J's RuleBasedCollator does not support turning off the Thai/Lao vowel-consonant swapping, since the UCA clearly states that it has to be supported to ensure a correct sorting order. If a '!' is encountered, it is ignored.
Examples
Creating Customized RuleBasedCollators:
Concatenating rules to combineString simple = "& a < b < c < d"; RuleBasedCollator simpleCollator = new RuleBasedCollator(simple); String norwegian = "& a , A < b , B < c , C < d , D < e , E " + "< f , F < g , G < h , H < i , I < j , " + "J < k , K < l , L < m , M < n , N < " + "o , O < p , P < q , Q < r , R < s , S < " + "t , T < u , U < v , V < w , W < x , X " + "< y , Y < z , Z < \u00E5 = a\u030A " + ", \u00C5 = A\u030A ; aa , AA < \u00E6 " + ", \u00C6 < \u00F8 , \u00D8"; RuleBasedCollator norwegianCollator = new RuleBasedCollator(norwegian);
Collator
s:
Making changes to an existing RuleBasedCollator to create a new// Create an en_US Collator object RuleBasedCollator en_USCollator = (RuleBasedCollator) Collator.getInstance(new Locale("en", "US", "")); // Create a da_DK Collator object RuleBasedCollator da_DKCollator = (RuleBasedCollator) Collator.getInstance(new Locale("da", "DK", "")); // Combine the two // First, get the collation rules from en_USCollator String en_USRules = en_USCollator.getRules(); // Second, get the collation rules from da_DKCollator String da_DKRules = da_DKCollator.getRules(); RuleBasedCollator newCollator = new RuleBasedCollator(en_USRules + da_DKRules); // newCollator has the combined rules
Collator
object, by appending changes to the existing rule:
How to change the order of non-spacing accents:// Create a new Collator object with additional rules String addRules = "& C < ch, cH, Ch, CH"; RuleBasedCollator myCollator = new RuleBasedCollator(en_USCollator + addRules); // myCollator contains the new rules
Putting in a new primary ordering before the default setting, e.g. sort English characters before or after Japanese characters in the Japanese// old rule with main accents String oldRules = "= \u0301 ; \u0300 ; \u0302 ; \u0308 " + "; \u0327 ; \u0303 ; \u0304 ; \u0305 " + "; \u0306 ; \u0307 ; \u0309 ; \u030A " + "; \u030B ; \u030C ; \u030D ; \u030E " + "; \u030F ; \u0310 ; \u0311 ; \u0312 " + "< a , A ; ae, AE ; \u00e6 , \u00c6 " + "< b , B < c, C < e, E & C < d , D"; // change the order of accent characters String addOn = "& \u0300 ; \u0308 ; \u0302"; RuleBasedCollator myCollator = new RuleBasedCollator(oldRules + addOn);
Collator
:
// get en_US Collator rules RuleBasedCollator en_USCollator = (RuleBasedCollator)Collator.getInstance(Locale.US); // add a few Japanese characters to sort before English characters // suppose the last character before the first base letter 'a' in // the English collation rule is \u2212 String jaString = "& \u2212 < \u3041, \u3042 < \u3043, " + "\u3044"; RuleBasedCollator myJapaneseCollator = new RuleBasedCollator(en_USCollator.getRules() + jaString);
This class is not subclassable
UNKNOWN: ICU 2.8
Constructor Summary | |
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RuleBasedCollator(String rules) Constructor that takes the argument rules for customization. |
Method Summary | |
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Object | clone()
Clones the RuleBasedCollator |
int | compare(String source, String target)
Compares the source text String to the target text String according to
the collation rules, strength and decomposition mode for this
RuleBasedCollator.
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boolean | equals(Object obj)
Compares the equality of two RuleBasedCollator objects.
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CollationElementIterator | getCollationElementIterator(String source)
Return a CollationElementIterator for the given String. |
CollationElementIterator | getCollationElementIterator(CharacterIterator source)
Return a CollationElementIterator for the given CharacterIterator.
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CollationElementIterator | getCollationElementIterator(UCharacterIterator source)
Return a CollationElementIterator for the given UCharacterIterator.
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CollationKey | getCollationKey(String source) Get a Collation key for the argument String source from this RuleBasedCollator. |
void | getContractionsAndExpansions(UnicodeSet contractions, UnicodeSet expansions, boolean addPrefixes)
Gets unicode sets containing contractions and/or expansions of a collator |
boolean | getNumericCollation()
Method to retrieve the numeric collation value.
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RawCollationKey | getRawCollationKey(String source, RawCollationKey key)
Gets the simpler form of a CollationKey for the String source following
the rules of this Collator and stores the result into the user provided
argument key.
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String | getRules()
Gets the collation rules for this RuleBasedCollator.
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String | getRules(boolean fullrules)
Returns current rules. |
UnicodeSet | getTailoredSet()
Get an UnicodeSet that contains all the characters and sequences
tailored in this collator. |
VersionInfo | getUCAVersion()
Get the UCA version of this collator object. |
int | getVariableTop()
Gets the variable top value of a Collator.
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VersionInfo | getVersion()
Get the version of this collator object. |
int | hashCode()
Generates a unique hash code for this RuleBasedCollator. |
boolean | isAlternateHandlingShifted()
Checks if the alternate handling behaviour is the UCA defined SHIFTED or
NON_IGNORABLE.
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boolean | isCaseLevel()
Checks if case level is set to true.
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boolean | isFrenchCollation()
Checks if French Collation is set to true.
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boolean | isHiraganaQuaternary()
Checks if the Hiragana Quaternary mode is set on.
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boolean | isLowerCaseFirst()
Return true if a lowercase character is sorted before the corresponding uppercase character.
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boolean | isUpperCaseFirst()
Return true if an uppercase character is sorted before the corresponding lowercase character.
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void | setAlternateHandlingDefault()
Sets the alternate handling mode to the initial mode set during
construction of the RuleBasedCollator.
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void | setAlternateHandlingShifted(boolean shifted)
Sets the alternate handling for QUATERNARY strength to be either
shifted or non-ignorable.
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void | setCaseFirstDefault()
Sets the case first mode to the initial mode set during
construction of the RuleBasedCollator.
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void | setCaseLevel(boolean flag) When case level is set to true, an additional weight is formed between the SECONDARY and TERTIARY weight, known as the case level. |
void | setCaseLevelDefault()
Sets the case level mode to the initial mode set during
construction of the RuleBasedCollator.
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void | setDecompositionDefault()
Sets the decomposition mode to the initial mode set during construction
of the RuleBasedCollator.
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void | setFrenchCollation(boolean flag)
Sets the mode for the direction of SECONDARY weights to be used in
French collation.
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void | setFrenchCollationDefault()
Sets the French collation mode to the initial mode set during
construction of the RuleBasedCollator.
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void | setHiraganaQuaternary(boolean flag)
Sets the Hiragana Quaternary mode to be on or off.
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void | setHiraganaQuaternaryDefault()
Sets the Hiragana Quaternary mode to the initial mode set during
construction of the RuleBasedCollator.
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void | setLowerCaseFirst(boolean lowerfirst)
Sets the orders of lower cased characters to sort before upper cased
characters, in strength TERTIARY. |
void | setNumericCollation(boolean flag)
When numeric collation is turned on, this Collator generates a collation
key for the numeric value of substrings of digits. |
void | setNumericCollationDefault()
Method to set numeric collation to its default value.
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void | setStrength(int newStrength) Sets this Collator's strength property. |
void | setStrengthDefault()
Sets the collation strength to the initial mode set during the
construction of the RuleBasedCollator.
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void | setUpperCaseFirst(boolean upperfirst)
Sets whether uppercase characters sort before lowercase
characters or vice versa, in strength TERTIARY. |
int | setVariableTop(String varTop) Variable top is a two byte primary value which causes all the codepoints with primary values that are less or equal than the variable top to be shifted when alternate handling is set to SHIFTED. |
void | setVariableTop(int varTop)
Sets the variable top to a collation element value supplied.
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Constructor that takes the argument rules for customization. The collator will be based on UCA, with the attributes and re-ordering of the characters specified in the argument rules.
See the user guide's section on Collation Customization for details on the rule syntax.
Parameters: rules the collation rules to build the collation table from.
Throws: ParseException and IOException thrown. ParseException thrown when argument rules have an invalid syntax. IOException thrown when an error occured while reading internal data.
UNKNOWN: ICU 2.8
Returns: a new instance of this RuleBasedCollator object
UNKNOWN: ICU 2.8
General recommendation:
If comparison are to be done to the same String multiple times, it would
be more efficient to generate CollationKeys for the Strings and use
CollationKey.compareTo(CollationKey) for the comparisons.
If speed performance is critical and object instantiation is to be
reduced, further optimization may be achieved by generating a simpler
key of the form RawCollationKey and reusing this RawCollationKey
object with the method RuleBasedCollator.getRawCollationKey. Internal
byte representation can be directly accessed via RawCollationKey and
stored for future use. Like CollationKey, RawCollationKey provides a
method RawCollationKey.compareTo for key comparisons.
If the each Strings are compared to only once, using the method
RuleBasedCollator.compare(String, String) will have a better performance.
Parameters: source the source text String. target the target text String.
Returns: 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.
See Also: CollationKey RuleBasedCollator
UNKNOWN: ICU 2.8
Parameters: obj the RuleBasedCollator to be compared to.
Returns: true if this RuleBasedCollator has exactly the same collation behaviour as obj, false otherwise.
UNKNOWN: ICU 2.8
See Also: CollationElementIterator
UNKNOWN: ICU 2.8
See Also: CollationElementIterator
UNKNOWN: ICU 2.8
See Also: CollationElementIterator
UNKNOWN: ICU 2.8
Get a Collation key for the argument String source from this RuleBasedCollator.
General recommendation:
If comparison are to be done to the same String multiple times, it would
be more efficient to generate CollationKeys for the Strings and use
CollationKey.compareTo(CollationKey) for the comparisons.
If the each Strings are compared to only once, using the method
RuleBasedCollator.compare(String, String) will have a better performance.
See the class documentation for an explanation about CollationKeys.
Parameters: source the text String to be transformed into a collation key.
Returns: the CollationKey for the given String based on this RuleBasedCollator's collation rules. If the source String is null, a null CollationKey is returned.
See Also: CollationKey RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Parameters: contractions if not null, set to contain contractions expansions if not null, set to contain expansions addPrefixes add the prefix contextual elements to contractions
Throws: Exception
UNKNOWN: ICU 3.4 This API might change or be removed in a future release.
Returns: true if numeric collation is turned on, false otherwise
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Parameters: source the text String to be transformed into a RawCollationKey key output RawCollationKey to store results
Returns: If key is null, a new instance of RawCollationKey will be created and returned, otherwise the user provided key will be returned.
See Also: RuleBasedCollator RuleBasedCollator RawCollationKey
UNKNOWN: ICU 2.8
Returns: returns the collation rules
See Also: RuleBasedCollator
UNKNOWN: ICU 2.8
Parameters: fullrules true if the rules that defines the full set of collation order is required, otherwise false for returning only the tailored rules
Returns: the current rules that defines this Collator.
See Also: getRules
UNKNOWN: ICU 2.6
Returns: a pointer to a UnicodeSet object containing all the code points and sequences that may sort differently than in the UCA.
Throws: ParseException thrown when argument rules have an invalid syntax. IOException
UNKNOWN: ICU 2.4
Returns: the version object associated with this collator
UNKNOWN: ICU 2.8
Returns: the variable top value of a Collator.
See Also: RuleBasedCollator
UNKNOWN: ICU 2.6
Returns: the version object associated with this collator
UNKNOWN: ICU 2.8
Returns: the unique hash code for this Collator
UNKNOWN: ICU 2.8
Returns: true or false
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Returns: the case level mode
See Also: RuleBasedCollator RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Returns: true if French Collation is set to true, false otherwise
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Returns: flag true if Hiragana Quaternary mode is on, false otherwise
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Returns: true lower cased characters are sorted before upper cased characters, false otherwise
See Also: RuleBasedCollator RuleBasedCollator RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Returns: true if upper cased characters are sorted before lower cased characters, false otherwise
See Also: RuleBasedCollator RuleBasedCollator RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
See Also: RuleBasedCollator isAlternateHandlingShifted
UNKNOWN: ICU 2.8
Parameters: shifted true if SHIFTED behaviour for alternate handling is desired, false for the NON_IGNORABLE behaviour.
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
See Also: RuleBasedCollator RuleBasedCollator RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
When case level is set to true, an additional weight is formed between the SECONDARY and TERTIARY weight, known as the case level. The case level is used to distinguish large and small Japanese Kana characters. Case level could also be used in other situations. For example to distinguish certain Pinyin characters. The default value is false, which means the case level is not generated. The contents of the case level are affected by the case first mode. A simple way to ignore accent differences in a string is to set the strength to PRIMARY and enable case level.
See the section on case level for more information.
Parameters: flag true if case level sorting is required, false otherwise
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Parameters: flag true to set the French collation on, false to set it off
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Parameters: flag true if Hiragana Quaternary mode is to be on, false otherwise
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Parameters: lowerfirst true for sorting lower cased characters before upper cased characters, false to ignore case preferences.
See Also: RuleBasedCollator RuleBasedCollator RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Parameters: flag true to turn numeric collation on and false to turn it off
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
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 the new strength value.
Throws: IllegalArgumentException If the new strength value is not one of PRIMARY, SECONDARY, TERTIARY, QUATERNARY or IDENTICAL.
See Also: RuleBasedCollator RuleBasedCollator RuleBasedCollator RuleBasedCollator RuleBasedCollator RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Parameters: upperfirst true to sort uppercase characters before lowercase characters, false to sort lowercase characters before uppercase characters
See Also: RuleBasedCollator RuleBasedCollator RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.8
Variable top is a two byte primary value which causes all the codepoints with primary values that are less or equal than the variable top to be shifted when alternate handling is set to SHIFTED.
Sets the variable top to a collation element value of a string supplied.
Parameters: varTop one or more (if contraction) characters to which the variable top should be set
Returns: a int value containing the value of the variable top in upper 16 bits. Lower 16 bits are undefined.
Throws: IllegalArgumentException is thrown if varTop argument is not
a valid variable top element. A variable top element is
invalid when
See Also: RuleBasedCollator RuleBasedCollator
UNKNOWN: ICU 2.6
Parameters: varTop Collation element value, as returned by setVariableTop or getVariableTop
See Also: RuleBasedCollator setVariableTop
UNKNOWN: ICU 2.6