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
*/
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
*/
public enum Form {
/**
* Canonical decomposition.
*/
NFD(android.icu.text.Normalizer.NFD),
/**
* Canonical decomposition, followed by canonical composition.
*/
NFC(android.icu.text.Normalizer.NFC),
/**
* Compatibility decomposition.
*/
NFKD(android.icu.text.Normalizer.NFKD),
/**
* Compatibility decomposition, followed by canonical composition.
*/
NFKC(android.icu.text.Normalizer.NFKC);
private final android.icu.text.Normalizer.Mode icuMode;
Form(android.icu.text.Normalizer.Mode icuMode) {
this.icuMode = icuMode;
}
}
/**
* 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 src or form
* is null.
*/
public static String normalize(CharSequence src, Form form) {
return android.icu.text.Normalizer.normalize(src.toString(), form.icuMode);
}
/**
* 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 src or form
* is null.
*/
public static boolean isNormalized(CharSequence src, Form form) {
return android.icu.text.Normalizer.isNormalized(src.toString(), form.icuMode, 0);
}
}