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package java.text;
import jdk.internal.icu.text.NormalizerBase;
This class provides the method normalize which transforms Unicode text into an equivalent composed or decomposed form, allowing for easier sorting and searching of text. The normalize method supports the standard normalization forms described in
Unicode Standard Annex #15 — Unicode Normalization Forms.
Characters with accents or other adornments can be encoded in
several different ways in Unicode. For example, take the character A-acute.
In Unicode, this can be encoded as a single character (the "composed" form):
U+00C1 LATIN CAPITAL LETTER A WITH ACUTE
or as two separate characters (the "decomposed" form):
U+0041 LATIN CAPITAL LETTER A
U+0301 COMBINING ACUTE ACCENT
To a user of your program, however, both of these sequences should be
treated as the same "user-level" character "A with acute accent". When you
are searching or comparing text, you must ensure that these two sequences are
treated as equivalent. In addition, you must handle characters with more than
one accent. Sometimes the order of a character's combining accents is
significant, while in other cases accent sequences in different orders are
really equivalent.
Similarly, the string "ffi" can be encoded as three separate letters:
U+0066 LATIN SMALL LETTER F
U+0066 LATIN SMALL LETTER F
U+0069 LATIN SMALL LETTER I
or as the single character
U+FB03 LATIN SMALL LIGATURE FFI
The ffi ligature is not a distinct semantic character, and strictly speaking
it shouldn't be in Unicode at all, but it was included for compatibility
with existing character sets that already provided it. The Unicode standard
identifies such characters by giving them "compatibility" decompositions
into the corresponding semantic characters. When sorting and searching, you
will often want to use these mappings.
The normalize method helps solve these problems by transforming text into the canonical composed and decomposed forms as shown in the first example above. In addition, you can have it perform compatibility decompositions so that you can treat compatibility characters the same as their equivalents. Finally, the normalize method rearranges accents into the proper canonical order, so that you do not have to worry about accent rearrangement on your own.
The W3C generally recommends to exchange texts in NFC.
Note also that most legacy character encodings use only precomposed forms and
often do not encode any combining marks by themselves. For conversion to such
character encodings the Unicode text needs to be normalized to NFC.
For more usage examples, see the Unicode Standard Annex.
Since: 1.6
/**
* This class provides the method {@code normalize} which transforms Unicode
* text into an equivalent composed or decomposed form, allowing for easier
* sorting and searching of text.
* The {@code normalize} method supports the standard normalization forms
* described in
* <a href="http://www.unicode.org/unicode/reports/tr15/tr15-23.html">
* Unicode Standard Annex #15 — Unicode Normalization Forms</a>.
* <p>
* Characters with accents or other adornments can be encoded in
* several different ways in Unicode. For example, take the character A-acute.
* In Unicode, this can be encoded as a single character (the "composed" form):
*
* <pre>
* U+00C1 LATIN CAPITAL LETTER A WITH ACUTE</pre>
*
* or as two separate characters (the "decomposed" form):
*
* <pre>
* U+0041 LATIN CAPITAL LETTER A
* U+0301 COMBINING ACUTE ACCENT</pre>
*
* To a user of your program, however, both of these sequences should be
* treated as the same "user-level" character "A with acute accent". When you
* are searching or comparing text, you must ensure that these two sequences are
* treated as equivalent. In addition, you must handle characters with more than
* one accent. Sometimes the order of a character's combining accents is
* significant, while in other cases accent sequences in different orders are
* really equivalent.
* <p>
* Similarly, the string "ffi" can be encoded as three separate letters:
*
* <pre>
* U+0066 LATIN SMALL LETTER F
* U+0066 LATIN SMALL LETTER F
* U+0069 LATIN SMALL LETTER I</pre>
*
* or as the single character
*
* <pre>
* U+FB03 LATIN SMALL LIGATURE FFI</pre>
*
* The ffi ligature is not a distinct semantic character, and strictly speaking
* it shouldn't be in Unicode at all, but it was included for compatibility
* with existing character sets that already provided it. The Unicode standard
* identifies such characters by giving them "compatibility" decompositions
* into the corresponding semantic characters. When sorting and searching, you
* will often want to use these mappings.
* <p>
* The {@code normalize} method helps solve these problems by transforming
* text into the canonical composed and decomposed forms as shown in the first
* example above. In addition, you can have it perform compatibility
* decompositions so that you can treat compatibility characters the same as
* their equivalents.
* Finally, the {@code normalize} method rearranges accents into the
* proper canonical order, so that you do not have to worry about accent
* rearrangement on your own.
* <p>
* The W3C generally recommends to exchange texts in NFC.
* Note also that most legacy character encodings use only precomposed forms and
* often do not encode any combining marks by themselves. For conversion to such
* character encodings the Unicode text needs to be normalized to NFC.
* For more usage examples, see the Unicode Standard Annex.
*
* @since 1.6
*/
public final class Normalizer {
private Normalizer() {};
This enum provides constants of the four Unicode normalization forms
that are described in
Unicode Standard Annex #15 — Unicode Normalization Forms
and two methods to access them.
Since: 1.6
/**
* This enum provides constants of the four Unicode normalization forms
* that are described in
* <a href="http://www.unicode.org/unicode/reports/tr15/tr15-23.html">
* Unicode Standard Annex #15 — Unicode Normalization Forms</a>
* and two methods to access them.
*
* @since 1.6
*/
public static enum Form {
Canonical decomposition.
/**
* Canonical decomposition.
*/
NFD,
Canonical decomposition, followed by canonical composition.
/**
* Canonical decomposition, followed by canonical composition.
*/
NFC,
Compatibility decomposition.
/**
* Compatibility decomposition.
*/
NFKD,
Compatibility decomposition, followed by canonical composition.
/**
* Compatibility decomposition, followed by canonical composition.
*/
NFKC
}
Normalize a sequence of char values.
The sequence will be normalized according to the specified normalization
from.
Params: Throws: - NullPointerException – If
src or form is null.
Returns: The normalized String
/**
* Normalize a sequence of char values.
* The sequence will be normalized according to the specified normalization
* from.
* @param src The sequence of char values to normalize.
* @param form The normalization form; one of
* {@link java.text.Normalizer.Form#NFC},
* {@link java.text.Normalizer.Form#NFD},
* {@link java.text.Normalizer.Form#NFKC},
* {@link java.text.Normalizer.Form#NFKD}
* @return The normalized String
* @throws NullPointerException If {@code src} or {@code form}
* is null.
*/
public static String normalize(CharSequence src, Form form) {
return NormalizerBase.normalize(src.toString(), form);
}
Determines if the given sequence of char values is normalized.
Params: Throws: - NullPointerException – If
src or form is null.
Returns: true if the sequence of char values is normalized;
false otherwise.
/**
* Determines if the given sequence of char values is normalized.
* @param src The sequence of char values to be checked.
* @param form The normalization form; one of
* {@link java.text.Normalizer.Form#NFC},
* {@link java.text.Normalizer.Form#NFD},
* {@link java.text.Normalizer.Form#NFKC},
* {@link java.text.Normalizer.Form#NFKD}
* @return true if the sequence of char values is normalized;
* false otherwise.
* @throws NullPointerException If {@code src} or {@code form}
* is null.
*/
public static boolean isNormalized(CharSequence src, Form form) {
return NormalizerBase.isNormalized(src.toString(), form);
}
}