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java.lang.Object | +--com.ibm.icu4jni.text.Collator | +--com.ibm.icu4jni.text.RuleBasedCollator
Concrete implementation class for Collation.
The collation table is composed of a list of collation rules, where each rule is of three forms:
< modifier > < relation > < text-argument > < reset > < text-argument >
RuleBasedCollator
has the following restrictions for efficiency
(other subclasses may be used for more complex languages) :
b c
is
treated as bc
.
'@' : Indicates that accents are sorted backwards, as in French.
'&' : Indicates that the next rule follows the position to where the reset text-argument would be sorted.
This sounds more complicated than it is in practice. For example, the following are equivalent ways of expressing the same thing:
Notice that the order is important, as the subsequent item goes immediately after the text-argument. The following are not equivalent:a < b < c a < b & b < c a < c & a < b
Either the text-argument must already be present in the sequence, or some initial substring of the text-argument must be present. (e.g. "a < b & ae < e" is valid since "a" is present in the sequence before "ae" is reset). In this latter case, "ae" is not entered and treated as a single character; instead, "e" is sorted as if it were expanded to two characters: "a" followed by an "e". This difference appears in natural languages: in traditional Spanish "ch" is treated as though it contracts to a single character (expressed as "c < ch < d"), while in traditional German a-umlaut is treated as though it expanded to two characters (expressed as "a,A < b,B ... & ae;? & AE;?"). [? and ? are, of course, the escape sequences for a-umlaut.]a < b & a < c a < c & a < b
Ignorable Characters
For ignorable characters, the first rule must start with a relation (the examples we have used above are really fragments; "a < b" really should be "< a < b"). If, however, the first relation is not "<", then all the all text-arguments up to the first "<" are ignorable. For example, ", - < a < b" makes "-" an ignorable character, as we saw earlier in the word "black-birds". In the samples for different languages, you see that most accents are ignorable.
Normalization and Accents
RuleBasedCollator
automatically processes its rule table to
include both pre-composed and combining-character versions of accented
characters. Even if the provided rule string contains only base characters
and separate combining accent characters, the pre-composed accented
characters matching all canonical combinations of characters from the rule
string will be entered in the table.
This allows you to use a RuleBasedCollator to compare accented strings even when the collator is set to NO_DECOMPOSITION. However, if the strings to be collated contain combining sequences that may not be in canonical order, you should set the collator to CANONICAL_DECOMPOSITION to enable sorting of combining sequences. For more information, see The Unicode Standard, Version 3.0.)
Errors
The following are errors:
RuleBasedCollator
throws
a ParseException
.
Examples
Simple: "< a < b < c < d"
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 < ?=a?,?=A? ;aa,AA< ?,?< ?,?"
Normally, to create a rule-based Collator object, you will use
Collator
's factory method getInstance
.
However, to create a rule-based Collator object with specialized rules
tailored to your needs, you construct the RuleBasedCollator
with the rules contained in a String
object. For example:
Or:String Simple = "< a < b < c < d"; RuleBasedCollator mySimple = 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" + "< ?=a?,?=A?" + ";aa,AA< ?,?< ?,?"; RuleBasedCollator myNorwegian = new RuleBasedCollator(Norwegian);
Combining Collator
s is as simple as concatenating strings.
Here's an example that combines two Collator
s from two
different locales:
// 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
Another more interesting example would be to make changes on an existing
table to create a new Collator
object. For example, add
"& C < ch, cH, Ch, CH" to the en_USCollator
object to create
your own:
// 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
The following example demonstrates how to change the order of non-spacing accents,
// old rule String oldRules = "=?;?;?" // main accents Diaeresis 00A8, Macron 00AF // Acute 00BF + "< a , A ; ae, AE ; ? , ?" + "< b , B < c, C < e, E & C < d, D"; // change the order of accent characters String addOn = "& ?;?;?;"; // Acute 00BF, Macron 00AF, Diaeresis 00A8 RuleBasedCollator myCollator = new RuleBasedCollator(oldRules + addOn);
The last example shows how to put new primary ordering in before the
default setting. For example, in Japanese Collator
, you
can either sort English characters before or after Japanese characters,
// get en_US Collator rules RuleBasedCollator en_USCollator = (RuleBasedCollator)Collator.getInstance(Locale.US); // add a few Japanese character to sort before English characters // suppose the last character before the first base letter 'a' in // the English collation rule is ? String jaString = "& \\u30A2 , \\u30FC < \\u30C8"; RuleBasedCollator myJapaneseCollator = new RuleBasedCollator(en_USCollator.getRules() + jaString);
Field Summary |
Fields inherited from class com.ibm.icu4jni.text.Collator |
CANONICAL_DECOMPOSITION, IDENTICAL, NO_DECOMPOSITION, PRIMARY, QUATERNARY, RESULT_DEFAULT, RESULT_EQUAL, RESULT_GREATER, RESULT_LESS, SECONDARY, TERTIARY |
Constructor Summary | |
RuleBasedCollator(java.lang.String rules)
RuleBasedCollator constructor. |
|
RuleBasedCollator(java.lang.String rules,
int strength)
RuleBasedCollator constructor. |
|
RuleBasedCollator(java.lang.String rules,
int normalizationmode,
int strength)
RuleBasedCollator constructor. |
Method Summary | |
java.lang.Object |
clone()
Makes a complete copy of the current object. |
int |
compare(java.lang.String source,
java.lang.String target)
The comparison function compares the character data stored in two different strings. |
boolean |
equals(java.lang.Object target)
Checks if argument object is equals to this object. |
protected void |
finalize()
Garbage collection. |
int |
getAttribute(int type)
Gets the attribute to be used in comparison or transformation. |
CollationElementIterator |
getCollationElementIterator(java.lang.String source)
Create a CollationElementIterator object that will iterator over the elements in a string, using the collation rules defined in this RuleBasedCollator |
CollationKey |
getCollationKey(java.lang.String source)
Get the sort key as an CollationKey object from the argument string. |
int |
getDecomposition()
Get the normalization mode for this object. |
java.lang.String |
getRules()
Get the collation rules of this Collation object The rules will follow the rule syntax. |
byte[] |
getSortKey(java.lang.String source)
Get a sort key for the argument string Sort keys may be compared using java.util.Arrays.equals |
int |
getStrength()
Determines the minimum strength that will be use in comparison or transformation. |
int |
hashCode()
Returns a hash of this collation object Note this method is not complete, it only returns 0 at the moment. |
void |
setAttribute(int type,
int value)
Sets the attribute to be used in comparison or transformation. |
void |
setDecomposition(int decompositionmode)
Sets the decomposition mode of the Collator object on or off. |
void |
setStrength(int strength)
Sets the minimum strength to be used in comparison or transformation. |
Methods inherited from class com.ibm.icu4jni.text.Collator |
equals, getInstance, getInstance |
Methods inherited from class java.lang.Object |
getClass, notify, notifyAll, toString, wait, wait, wait |
Constructor Detail |
public RuleBasedCollator(java.lang.String rules) throws java.text.ParseException
rules
- the collation rules to build the collation table from.
java.text.ParseException
- thrown if rules are empty or a Runtime error
if collator can not be created.public RuleBasedCollator(java.lang.String rules, int strength) throws java.text.ParseException
rules
- the collation rules to build the collation table from.strength
- collation strength
java.text.ParseException
- thrown if rules are empty or a Runtime error
if collator can not be created.Collator.PRIMARY
,
Collator.SECONDARY
,
Collator.TERTIARY
,
Collator.QUATERNARY
,
Collator.IDENTICAL
public RuleBasedCollator(java.lang.String rules, int normalizationmode, int strength)
Note API change starting from release 2.4. Prior to release 2.4, the normalizationmode argument values are from the class com.ibm.icu4jni.text.Normalization. In 2.4, the valid normalizationmode arguments for this API are CollationAttribute.VALUE_ON and CollationAttribute.VALUE_OFF.
rules
- the collation rules to build the collation table from.strength
- collation strengthnormalizationmode
- normalization mode
thrown
- when constructor error occursCollator.PRIMARY
,
Collator.SECONDARY
,
Collator.TERTIARY
,
Collator.QUATERNARY
,
Collator.IDENTICAL
,
Collator.CANONICAL_DECOMPOSITION
,
Collator.NO_DECOMPOSITION
Method Detail |
public java.lang.Object clone()
clone
in class Collator
public int compare(java.lang.String source, java.lang.String target)
Example of use:
. Collator myCollation = Collator.createInstance(Locale::US); . myCollation.setStrength(CollationAttribute.VALUE_PRIMARY); . // result would be Collator.RESULT_EQUAL ("abc" == "ABC") . // (no primary difference between "abc" and "ABC") . int result = myCollation.compare("abc", "ABC",3); . myCollation.setStrength(CollationAttribute.VALUE_TERTIARY); . // result would be Collation::LESS (abc" <<< "ABC") . // (with tertiary difference between "abc" and "ABC") . int result = myCollation.compare("abc", "ABC",3);
compare
in class Collator
source
- The source string.target
- The target string.
public int getDecomposition()
getDecomposition
in class Collator
Collator.CANONICAL_DECOMPOSITION
,
Collator.NO_DECOMPOSITION
public void setDecomposition(int decompositionmode)
Sets the decomposition mode of the Collator object on or off. If the decomposition mode is set to on, string would be decomposed into NFD format where necessary before sorting.
setDecomposition
in class Collator
decompositionmode
- the new decomposition modeCollator.CANONICAL_DECOMPOSITION
,
Collator.NO_DECOMPOSITION
public int getStrength()
E.g. with strength == CollationAttribute.VALUE_SECONDARY, the tertiary difference is ignored
E.g. with strength == PRIMARY, the secondary and tertiary difference are ignored.
getStrength
in class Collator
Collator.PRIMARY
,
Collator.SECONDARY
,
Collator.TERTIARY
,
Collator.QUATERNARY
,
Collator.IDENTICAL
public void setStrength(int strength)
Example of use:
. Collator myCollation = Collator.createInstance(Locale::US); . myCollation.setStrength(PRIMARY); . // result will be "abc" == "ABC" . // tertiary differences will be ignored . int result = myCollation->compare("abc", "ABC");
setStrength
in class Collator
strength
- the new comparison level.
thrown
- when argument does not belong to any collation strength
mode or error occurs while setting data.Collator.PRIMARY
,
Collator.SECONDARY
,
Collator.TERTIARY
,
Collator.QUATERNARY
,
Collator.IDENTICAL
public void setAttribute(int type, int value)
Example of use:
. Collator myCollation = Collator.createInstance(Locale::US); . myCollation.setAttribute(CollationAttribute.CASE_LEVEL, . CollationAttribute.VALUE_ON); . int result = myCollation->compare("\\u30C3\\u30CF", . "\\u30C4\\u30CF"); . // result will be Collator.RESULT_LESS.
setAttribute
in class Collator
type
- the attribute to be set from CollationAttributevalue
- attribute value from CollationAttributepublic int getAttribute(int type)
getAttribute
in class Collator
type
- the attribute to be set from CollationAttribute
public CollationKey getCollationKey(java.lang.String source)
Collator collator = Collator.getInstance();
byte[] array = collator.getSortKey(source);
getCollationKey
in class Collator
source
- string to be processed.
public byte[] getSortKey(java.lang.String source)
source
- string for key to be generated
public java.lang.String getRules()
public CollationElementIterator getCollationElementIterator(java.lang.String source)
source
- string to iterate over
thrown
- when error occurspublic int hashCode()
hashCode
in class Collator
public boolean equals(java.lang.Object target)
equals
in class Collator
target
- object
protected void finalize()
finalize
in class java.lang.Object
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