20.5 The Class java.lang.Character

public final class Character {
	public static final char MIN_VALUE = '\u0000';
	public static final char MAX_VALUE = '\uffff';
	public static final int MIN_RADIX = 2;
	public static final int MAX_RADIX = 36;
	public Character(char value);
	public String toString();
	public boolean equals(Object obj);
	public int hashCode();
	public char charValue();
	public static boolean isDefined(char ch);
	public static boolean isLowerCase(char ch);
	public static boolean isUpperCase(char ch);
	public static boolean isTitleCase(char ch);
	public static boolean isDigit(char ch);
	public static boolean isLetter(char ch);
	public static boolean isLetterOrDigit(char ch);
	public static boolean isJavaLetter(char ch);
	public static boolean isJavaLetterOrDigit(char ch);)
	public static boolean isSpace(char ch);
	public static char toLowerCase(char ch);
	public static char toUpperCase(char ch);
	public static char toTitleCase(char ch);
	public static int digit(char ch, int radix);
	public static char forDigit(int digit, int radix);
}

The Unicode 1.1.5 attribute table is available on the World Wide Web as:

ftp://unicode.org/pub/MappingTables/UnicodeData-1.1.5.txt

• The following entries should have titlecase mappings as shown here:

  03D0;GREEK BETA SYMBOL;Ll;0;L;;;;;N;GREEK SMALL LETTER CURLED BETA;;0392;;0392

  03D1;GREEK THETA SYMBOL;Ll;0;L;;;;;N;GREEK SMALL LETTER SCRIPT THETA;;0398;;0398

  03D5;GREEK PHI SYMBOL;Ll;0;L;;;;;N;GREEK SMALL LETTER SCRIPT PHI;;03A6;;03A6

  03D6;GREEK PI SYMBOL;Ll;0;L;;;;;N;GREEK SMALL LETTER OMEGA PI;;03A0;;03A0

  03F0;GREEK KAPPA SYMBOL;Ll;0;L;;;;;N;GREEK SMALL LETTER SCRIPT KAPPA;;039A;;039A

  03F1;GREEK RHO SYMBOL;Ll;0;L;;;;;N;GREEK SMALL LETTER TAILED RHO;;03A1;;03A1

• The following entries should have numeric values as shown here:

  FF10;FULLWIDTH DIGIT ZERO;Nd;0;EN;0030;0;0;0;N;;;;;

  FF11;FULLWIDTH DIGIT ONE;Nd;0;EN;0031;1;1;1;N;;;;;

  FF12;FULLWIDTH DIGIT TWO;Nd;0;EN;0032;2;2;2;N;;;;;

  FF13;FULLWIDTH DIGIT THREE;Nd;0;EN;0033;3;3;3;N;;;;;

  FF14;FULLWIDTH DIGIT FOUR;Nd;0;EN;0034;4;4;4;N;;;;;

  FF15;FULLWIDTH DIGIT FIVE;Nd;0;EN;0035;5;5;5;N;;;;;

  FF16;FULLWIDTH DIGIT SIX;Nd;0;EN;0036;6;6;6;N;;;;;

  FF17;FULLWIDTH DIGIT SEVEN;Nd;0;EN;0037;7;7;7;N;;;;;

  FF18;FULLWIDTH DIGIT EIGHT;Nd;0;EN;0038;8;8;8;N;;;;;

  FF19;FULLWIDTH DIGIT NINE;Nd;0;EN;0039;9;9;9;N;;;;;

• The following entries should have no lowercase equivalents:

  03DA;GREEK LETTER STIGMA;Lu;0;L;;;;;N;GREEK CAPITAL LETTER STIGMA;;;;

  03DC;GREEK LETTER DIGAMMA;Lu;0;L;;;;;N;GREEK CAPITAL LETTER DIGAMMA;;;;

  03DE;GREEK LETTER KOPPA;Lu;0;L;;;;;N;GREEK CAPITAL LETTER KOPPA;;;;

  03E0;GREEK LETTER SAMPI;Lu;0;L;;;;;N;GREEK CAPITAL LETTER SAMPI;;;;

• This entry should have uppercase and titlecase equivalents as shown here:

  03C2;GREEK SMALL LETTER FINAL SIGMA;Ll;0;L;;;;;N;;;03A3;;03A3

Java 1.1 will include the methods defined here, either based on Unicode 1.1.5 or, we hope, updated versions of the methods that use the newer Unicode 2.0. The character attribute table for Unicode 2.0 is currently available on the World Wide Web as the file:

ftp://unicode.org/pub/MappingTables/UnicodeData-2.0.12.txt

http://java.sun.com/Series

The biggest change in Unicode 2.0 is a complete rearrangement of the Korean Hangul characters. There are numerous smaller improvements as well.

It is our intention that Java will track Unicode as it evolves over time. Given that full Unicode support is just emerging in the marketplace, and that changes in Unicode are in areas which are not yet widely used, this should cause minimal problems and further Java's goal of worldwide language support.

20.5.1 public static final char MIN_VALUE = '\u0000';

The constant value of this field is the smallest value of type char.

[This field is scheduled for introduction in Java version 1.1.]

20.5.2 public static final char MAX_VALUE = '\uffff';

The constant value of this field is the smallest value of type char.

[This field is scheduled for introduction in Java version 1.1.]

20.5.3 public static final int MIN_RADIX = 2;

The constant value of this field is the smallest value permitted for the radix argument in radix-conversion methods such as the digit method (§20.5.23), the forDigit method (§20.5.24), and the toString method of class Integer (§20.7).

20.5.4 public static final int MAX_RADIX = 36;

The constant value of this field is the largest value permitted for the radix argument in radix-conversion methods such as the digit method (§20.5.23), the forDigit method (§20.5.24), and the toString method of class Integer (§20.7).

20.5.5 public Character(char value)

This constructor initializes a newly created Character object so that it represents the primitive value that is the argument.

20.5.6 public String toString()

The result is a String whose length is 1 and whose sole component is the primitive char value represented by this Character object.

Overrides the toString method of Object (§20.1.2).

20.5.7 public boolean equals(Object obj)

The result is true if and only if the argument is not null and is a Character object that represents the same char value as this Character object.

Overrides the equals method of Object (§20.1.3).

20.5.8 public int hashCode()

The result is the primitive char value represented by this Character object, cast to type int.

Overrides the hashCode method of Object (§20.1.4).

20.5.9 public char charValue()

The primitive char value represented by this Character object is returned.

20.5.10 public static boolean isDefined(char ch)

The result is true if and only if the character argument is a defined Unicode character.

A character is a defined Unicode character if and only if at least one of the following is true:

• It has an entry in the Unicode attribute table.
• It is not less than \u3040 and not greater than \u9FA5.
• It is not less than \uF900 and not greater than \uFA2D.

[This method is scheduled for introduction in Java version 1.1, either as defined here, or updated for Unicode 2.0; see §20.5.]

20.5.11 public static boolean isLowerCase(char ch)

The result is true if and only if the character argument is a lowercase character.

A character is considered to be lowercase if and only if all of the following are true:

• The character ch is not in the range \u2000 through \u2FFF.
• The Unicode attribute table does not specify a mapping to lowercase for this character (the purpose of this requirement is to exclude titlecase characters).
• At least one of the following is true:
  • The Unicode attribute table specifies a mapping to uppercase for this character.
  • The name for the character in the Unicode attribute table contains the words SMALL LETTER or the words SMALL LIGATURE.

Of the first 128 Unicode characters, exactly 26 are considered to be lowercase:

abcdefghijklmnopqrstuvwxyz

20.5.12 public static boolean isUpperCase(char ch)

The result is true if and only if the character argument is an uppercase character.

A character is considered to be uppercase if and only if all of the following are true:

• The character ch is not in the range \u2000 through \u2FFF.
• The Unicode attribute table does not specify a mapping to uppercase for this character (the purpose of this requirement is to exclude titlecase characters).
• At least one of the following is true:
  • The Unicode attribute table specifies a mapping to lowercase for this character.
  • The name for the character in the Unicode attribute table contains the words CAPITAL LETTER or the words CAPITAL LIGATURE.

Of the first 128 Unicode characters, exactly 26 are considered to be uppercase:

ABCDEFGHIJKLMNOPQRSTUVWXYZ

20.5.13 public static boolean isTitleCase(char ch)

The result is true if and only if the character argument is a titlecase character.

The notion of "titlecase" was introduced into Unicode to handle a peculiar situation: there are single Unicode characters whose appearance in each case looks exactly like two ordinary Latin letters. For example, there is a single Unicode character `LJ' (\u01C7) that looks just like the characters `L' and `J' put together. There is a corresponding lowercase letter `lj' (\u01C9) as well. These characters are present in Unicode primarily to allow one-to-one translations from the Cyrillic alphabet, as used in Serbia, for example, to the Latin alphabet. Now suppose the word "LJUBINJE" (which has six characters, not eight, because two of them are the single Unicode characters `LJ' and `NJ', perhaps produced by one-to-one translation from the Cyrillic) is to be written as part of a book title, in capitals and lowercase. The strategy of making the first letter uppercase and the rest lowercase results in "LJubinje"-most unfortunate. The solution is that there must be a third form, called a titlecase form. The titlecase form of `LJ' is `Lj' (\u01C8) and the titlecase form of `NJ' is `Nj'. A word for a book title is then best rendered by converting the first letter to titlecase if possible, otherwise to uppercase; the remaining letters are then converted to lowercase.

A character is considered to be titlecase if and only if both of the following are true:

• The character ch is not in the range \u2000 through \u2FFF.
• The Unicode attribute table specifies a mapping to uppercase and a mapping to lowercase for this character.

\u01C5	    LATIN CAPITAL LETTER D WITH SMALL LETTER Z WITH CARON
\u01C8	    LATIN CAPITAL LETTER L WITH SMALL LETTER J
\u01CB	    LATIN CAPITAL LETTER N WITH SMALL LETTER J
\u01F2	    LATIN CAPITAL LETTER D WITH SMALL LETTER Z

20.5.14 public static boolean isDigit(char ch)

The result is true if and only if the character argument is a digit.

A character is considered to be a digit if and only if both of the following are true:

• The character ch is not in the range \u2000 through \u2FFF.
• The name for the character in the Unicode attribute table contains the word DIGIT.

0030-0039	ISO-Latin-1 (and ASCII) digits ('0'-'9')
0660-0669	Arabic-Indic digits
06F0-06F9	Eastern Arabic-Indic digits
0966-096F	Devanagari digits
09E6-09EF	Bengali digits
0A66-0A6F	Gurmukhi digits
0AE6-0AEF	Gujarati digits
0B66-0B6F	Oriya digits
0BE7-0BEF	Tamil digits (there are only nine of these-no zero digit)
0C66-0C6F	Telugu digits
0CE6-0CEF	Kannada digits
0D66-0D6F	Malayalam digits
0E50-0E59	Thai digits
0ED0-0ED9	Lao digits
FF10-FF19	Fullwidth digits

0123456789

20.5.15 public static boolean isLetter(char ch)

The result is true if and only if the character argument is a letter.

A character is considered to be a letter if and only if it is a letter or digit (§20.5.16) but is not a digit (§20.5.14).

[This method is scheduled for introduction in Java version 1.1, either as defined here, or updated for Unicode 2.0; see §20.5.]

20.5.16 public static boolean isLetterOrDigit(char ch)

The result is true if and only if the character argument is a letter-or-digit.

A character is considered to be a letter-or-digit if and only if it is a defined Unicode character (§20.5.10) and its code lies in one of the following ranges:

0030-0039	ISO-Latin-1 (and ASCII) digits ('0'-'9')
0041-005A	ISO-Latin-1 (and ASCII) uppercase Latin letters ('A'-'Z')
0061-007A	ISO-Latin-1 (and ASCII) lowercase Latin letters ('a'-'z')
00C0-00D6	ISO-Latin-1 supplementary letters
00D8-00F6	ISO-Latin-1 supplementary letters
00F8-00FF	ISO-Latin-1 supplementary letters
0100-1FFF	Latin extended-A, Latin extended-B, IPA extensions, 
spacing modifier letters, combining diacritical marks, basic 
Greek, Greek symbols and Coptic, Cyrillic, Armenian, 
Hebrew extended-A, Basic Hebrew, Hebrew extended-B, 
Basic Arabic, Arabic extended, Devanagari, Bengali, 
Gurmukhi, Gujarati, Oriya, Tamil, Telugu, Kannada, 
Malayalam, Thai, Lao, Basic Georgian, Georgian extended, 
Hanguljamo, Latin extended additional, Greek extended
3040-9FFF	Hiragana, Katakana, Bopomofo, Hangul compatibility 
Jamo, CJK miscellaneous, enclosed CJK characters and 
months, CJK compatibility, Hangul, Hangul 
supplementary-A, Hangul supplementary-B, CJK unified 
ideographs
F900-FDFF	CJK compatibility ideographs, alphabetic presentation 
forms, Arabic presentation forms-A
FE70-FEFE	Arabic presentation forms-B
FF10-FF19	Fullwidth digits
FF21-FF3A	Fullwidth Latin uppercase
FF41-FF5A	Fullwidth Latin lowercase
FF66-FFDC	Halfwidth Katakana and Hangul

[This method is scheduled for introduction in Java version 1.1, either as defined here, or updated for Unicode 2.0; see §20.5.]

20.5.17 public static boolean isJavaLetter(char ch)

The result is true if and only if the character argument is a character that can begin a Java identifier.

A character is considered to be a Java letter if and only if it is a letter (§20.5.15) or is the dollar sign character '$' (\u0024) or the underscore ("low line") character '_' (\u005F).

[This method is scheduled for introduction in Java version 1.1, either as defined here, or updated for Unicode 2.0; see §20.5.]

20.5.18 public static boolean isJavaLetterOrDigit(char ch)

The result is true if and only if the character argument is a character that can occur in a Java identifier after the first character.

A character is considered to be a Java letter-or-digit if and only if it is a letter-or-digit (§20.5.16) or is the dollar sign character '$' (\u0024) or the underscore ("low line") character '_' (\u005F).

[This method is scheduled for introduction in Java version 1.1, either as defined here, or updated for Unicode 2.0; see §20.5.]

20.5.19 public static boolean isSpace(char ch)

The result is true if the argument ch is one of the following characters:

'\t'		\u0009			HT		HORIZONTAL TABULATION
'\n'		\u000A			LF		LINE FEED (also known as NEW LINE)
'\f'		\u000C			FF		FORM FEED
'\r'		\u000D			CR		CARRIAGE RETURN
' '		\u0020			SP		SPACE

20.5.20 public static char toLowerCase(char ch)

If the character ch has a lowercase equivalent specified in the Unicode attribute table, then that lowercase equivalent character is returned. Otherwise, the argument ch is returned.

The lowercase equivalents specified in the Unicode attribute table, for Unicode 1.1.5 as corrected above, are as follows, where character codes to the right of arrows are the lowercase equivalents of character codes to the left of arrows: 0041-005A0061-007A, 00C0-00D600E0-00F6, 00D8-00DE00F8-00FE, 0100-012E0101-012F (evens to odds), 0132-01360133-0137 (evens to odds), 0139-0147013A-0148 (odds to evens), 014A-0176014B-0177 (evens to odds), 017800FF, 0179-017D017A-017E (odds to evens), 01810253, 01820183, 01840185, 01860254, 01870188, 018A0257, 018B018C, 018E0258, 018F0259, 0190025B, 01910192, 01930260, 01940263, 01960269, 01970268, 01980199, 019C026F, 019D0272, 01A0-01A401A1-01A5 (evens to odds), 01A701A8, 01A90283, 01AC01AD, 01AE0288, 01AF01B0, 01B1028A, 01B2028B, 01B301B4, 01B501B6, 01B70292, 01B801B9, 01BC01BD, 01C401C6, 01C501C6, 01C701C9, 01C801C9, 01CA01CC, 01CB-01DB01CC-01DC (odds to evens), 01DE-01EE01DF-01EF (evens to odds), 01F101F3, 01F201F3, 01F401F5, 01FA-021601FB-0217 (evens to odds), 038603AC, 0388-038A03AD-03AF, 038C03CC, 038E03CD, 038F03CE, 0391-03A103B1-03C1, 03A3-03AB03C3-03CB, 03E2-03EE03E3-03EF (evens to odds), 0401-040C0451-045C, 040E045E, 040F045F, 0410-042F0430-044F, 0460-04800461-0481 (evens to odds), 0490-04BE0491-04BF (evens to odds), 04C104C2, 04C304C4, 04C704C8, 04CB04CC, 04D0-04EA04D1-04EB (evens to odds), 04EE-04F404EF-04F5 (evens to odds), 04F804F9, 0531-05560561-0586, 10A0-10C510D0-10F5, 1E00-1E941E01-1E95 (evens to odds), 1EA0-1EF81EA1-1EF9 (evens to odds), 1F08-1F0F1F00-1F07, 1F18-1F1D1F10-1F15, 1F28-1F2F1F20-1F27, 1F38-1F3F1F30-1F37, 1F48-1F4D1F40-1F45, 1F591F51, 1F5B1F53, 1F5D1F55, 1F5F1F57, 1F68-1F6F1F60-1F67, 1F88-1F8F1F80-1F87, 1F98-1F9F1F90-1F97, 1FA8-1FAF1FA0-1FA7, 1FB81FB0, 1FB91FB1, 1FBA1F70, 1FBB1F71, 1FBC1FB3, 1FC8-1FCB1F72-1F75, 1FCC1FC3, 1FD81FD0, 1FD91FD1, 1FDA1F76, 1FDB1F77, 1FE81FE0, 1FE91FE1, 1FEA1F7A, 1FEB1F7B, 1FEC1FE5, 1FF81F78, 1FF91F79, 1FFA1F7C, 1FFB1F7D, 1FFC1FF3, 2160-216F2170-217F, 24B6-24CF24D0-24E9, FF21-FF3AFF41-FF5A.

Note that the method isLowerCase (§20.5.11) will not necessarily return true when given the result of the toLowerCase method.

[This specification for the method toLowerCase is scheduled for introduction in Java version 1.1, either as defined here, or updated for Unicode 2.0; see §20.5. In previous versions of Java, this method returns its argument for all arguments larger than \u00FF.]

20.5.21 public static char toUpperCase(char ch)

If the character ch has an uppercase equivalent specified in the Unicode attribute table, then that uppercase equivalent character is returned. Otherwise, the argument ch is returned.

The uppercase equivalents specified in the Unicode attribute table for Unicode 1.1.5 as corrected above, are as follows, where character codes to the right of arrows are the uppercase equivalents of character codes to the left of arrows: 0061-007A0041-005A, 00E0-00F600C0-00D6, 00F8-00FE00D8-00DE, 00FF0178, 0101-012F0100-012E (odds to evens), 0133-01370132-0136 (odds to evens), 013A-01480139-0147 (evens to odds), 014B-0177014A-0176 (odds to evens), 017A-017E0179-017D (evens to odds), 017F0053, 0183-01850182-0184 (odds to evens), 01880187, 018C018B, 01920191, 01990198, 01A1-01A501A0-01A4 (odds to evens), 01A801A7, 01AD01AC, 01B001AF, 01B401B3, 01B601B5, 01B901B8, 01BD01BC, 01C501C4, 01C601C4, 01C801C7, 01C901C7, 01CB01CA, 01CC01CA, 01CE-01DC01CD-01DB (evens to odds), 01DF-01EF01DE-01EE (odds to evens), 01F201F1, 01F301F1, 01F501F4, 01FB-021701FA-0216 (odds to evens), 02530181, 02540186, 0257018A, 0258018E, 0259018F, 025B0190, 02600193, 02630194, 02680197, 02690196, 026F019C, 0272019D, 028301A9, 028801AE, 028A01B1, 028B01B2, 029201B7, 03AC0386, 03AD-03AF0388-038A, 03B1-03C10391-03A1, 03C203A3, 03C3-03CB03A3-03AB, 03CC038C, 03CD038E, 03CE038F, 03D00392, 03D10398, 03D503A6, 03D603A0, 03E3-03EF03E2-03EE (odds to evens), 03F0039A, 03F103A1, 0430-044F0410-042F, 0451-045C0401-040C, 045E040E, 045F040F, 0461-04810460-0480 (odds to evens), 0491-04BF0490-04BE (odds to evens), 04C204C1, 04C404C3, 04C804C7, 04CC04CB, 04D1-04EB04D0-04EA (odds to evens), 04EF-04F504EE-04F4 (odds to evens), 04F904F8, 0561-05860531-0556, 1E01-1E951E00-1E94 (odds to evens), 1EA1-1EF91EA0-1EF8 (odds to evens), 1F00-1F071F08-1F0F, 1F10-1F151F18-1F1D, 1F20-1F271F28-1F2F, 1F30-1F371F38-1F3F, 1F40-1F451F48-1F4D, 1F511F59, 1F531F5B, 1F551F5D, 1F571F5F, 1F60-1F671F68-1F6F, 1F701FBA, 1F711FBB, 1F72-1F751FC8-1FCB, 1F761FDA, 1F771FDB, 1F781FF8, 1F791FF9, 1F7A1FEA, 1F7B1FEB, 1F7C1FFA, 1F7D1FFB, 1F80-1F871F88-1F8F, 1F90-1F971F98-1F9F, 1FA0-1FA71FA8-1FAF, 1FB01FB8, 1FB11FB9, 1FB31FBC, 1FC31FCC, 1FD01FD8, 1FD11FD9, 1FE01FE8, 1FE11FE9, 1FE51FEC, 1FF31FFC, 2170-217F2160-216F, 24D0-24E924B6-24CF, FF41-FF5AFF21-FF3A.

Note that the method isUpperCase (§20.5.12) will not necessarily return true when given the result of the toUpperCase method.

[This specification for the method toUpperCase is scheduled for introduction in Java version 1.1, either as defined here, or updated for Unicode 2.0; see §20.5. In previous versions of Java, this method returns its argument for all arguments larger than \u00FE. Note that although \u00FF is a lowercase character, its uppercase equivalent is \u0178; toUpperCase in versions of Java prior to version 1.1 simply do not consistently handle or use Unicode character codes above \u00FF.]

20.5.22 public static char toTitleCase(char ch)

If the character ch has a titlecase equivalent specified in the Unicode attribute table, then that titlecase equivalent character is returned; otherwise, the argument ch is returned.

Note that the method isTitleCase (§20.5.13) will not necessarily return true when given the result of the toTitleCase method. The Unicode attribute table always has the titlecase attribute equal to the uppercase attribute for characters that have uppercase equivalents but no separate titlecase form.

Example: Character.toTitleCase('a') returns 'A'

Example: Character.toTitleCase('Q') returns 'Q'

Example: Character.toTitleCase('lj') returns 'Lj' where 'lj' is the Unicode character \u01C9 and 'Lj' is its titlecase equivalent character \u01C8.

[This method is scheduled for introduction in Java version 1.1.]

20.5.23 public static int digit(char ch, int radix)

Returns the numeric value of the character ch considered as a digit in the specified radix. If the value of radix is not a valid radix, or the character ch is not a valid digit in the specified radix, then -1 is returned.

A radix is valid if and only if its value is not less than Character.MIN_RADIX (§20.5.3) and not greater than Character.MAX_RADIX (§20.5.4).

A character is a valid digit if and only if one of the following is true:

• The method isDigit returns true for the character, and the decimal digit value of the character, as specified in the Unicode attribute table, is less than the specified radix. In this case, the decimal digit value is returned.
• The character is one of the uppercase Latin letters 'A'-'Z' (\u0041-\u005A) and its code is less than radix+'A'-10. In this case ch-'A'+10 is returned.
• The character is one of the lowercase Latin letters 'a'-'z' (\u0061-\u007A) and its code is less than radix+'a'-10. In this case ch-'a'+10 is returned.

20.5.24 public static char forDigit(int digit, int radix)

Returns a character that represents the given digit in the specified radix. If the value of radix is not a valid radix, or the value of digit is not a valid digit in the specified radix, the null character '\u0000' is returned.

A radix is valid if and only if its value is not less than Character.MIN_RADIX (§20.5.3) and not greater than Character.MAX_RADIX (§20.5.4).

A digit is valid if and only if it is nonnegative and less than the radix.

If the digit is less than 10, then the character value '0'+digit is returned; otherwise, 'a'+digit-10 is returned. Thus, the digits produced by forDigit, in increasing order of value, are the ASCII characters:

0123456789abcdefghijklmnopqrstuvwxyz

Character.toUpperCase(Character.forDigit(digit, radix))

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Java Language Specification (HTML generated by Suzette Pelouch on February 24, 1998)
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