Character

public final class Character extends Object
implements Serializable Comparable<Character>

The Character class wraps a value of the primitive type char in an object. An object of type Character contains a single field whose type is char.

In addition, this class provides several methods for determining a character's category (lowercase letter, digit, etc.) and for converting characters from uppercase to lowercase and vice versa.

Character information is based on the Unicode Standard, version 6.2.0.

The methods and data of class Character are defined by the information in the UnicodeData file that is part of the Unicode Character Database maintained by the Unicode Consortium. This file specifies various properties including name and general category for every defined Unicode code point or character range.

The file and its description are available from the Unicode Consortium at:

Unicode Character Representations

The char data type (and therefore the value that a Character object encapsulates) are based on the original Unicode specification, which defined characters as fixed-width 16-bit entities. The Unicode Standard has since been changed to allow for characters whose representation requires more than 16 bits. The range of legal code points is now U+0000 to U+10FFFF, known as Unicode scalar value. (Refer to the definition of the U+n notation in the Unicode Standard.)

The set of characters from U+0000 to U+FFFF is sometimes referred to as the Basic Multilingual Plane (BMP). Characters whose code points are greater than U+FFFF are called supplementary characters. The Java platform uses the UTF-16 representation in char arrays and in the String and StringBuffer classes. In this representation, supplementary characters are represented as a pair of char values, the first from the high-surrogates range, (\uD800-\uDBFF), the second from the low-surrogates range (\uDC00-\uDFFF).

A char value, therefore, represents Basic Multilingual Plane (BMP) code points, including the surrogate code points, or code units of the UTF-16 encoding. An int value represents all Unicode code points, including supplementary code points. The lower (least significant) 21 bits of int are used to represent Unicode code points and the upper (most significant) 11 bits must be zero. Unless otherwise specified, the behavior with respect to supplementary characters and surrogate char values is as follows:

  • The methods that only accept a char value cannot support supplementary characters. They treat char values from the surrogate ranges as undefined characters. For example, Character.isLetter('\uD840') returns false, even though this specific value if followed by any low-surrogate value in a string would represent a letter.
  • The methods that accept an int value support all Unicode characters, including supplementary characters. For example, Character.isLetter(0x2F81A) returns true because the code point value represents a letter (a CJK ideograph).

In the Java SE API documentation, Unicode code point is used for character values in the range between U+0000 and U+10FFFF, and Unicode code unit is used for 16-bit char values that are code units of the UTF-16 encoding. For more information on Unicode terminology, refer to the Unicode Glossary.

Nested Class Summary

class Character.Subset Instances of this class represent particular subsets of the Unicode character set. 
class Character.UnicodeBlock A family of character subsets representing the character blocks in the Unicode specification. 
enum Character.UnicodeScript A family of character subsets representing the character scripts defined in the Unicode Standard Annex #24: Script Names

Constant Summary

int BYTES The number of bytes used to represent a char value in unsigned binary form.
byte COMBINING_SPACING_MARK General category "Mc" in the Unicode specification.
byte CONNECTOR_PUNCTUATION General category "Pc" in the Unicode specification.
byte CONTROL General category "Cc" in the Unicode specification.
byte CURRENCY_SYMBOL General category "Sc" in the Unicode specification.
byte DASH_PUNCTUATION General category "Pd" in the Unicode specification.
byte DECIMAL_DIGIT_NUMBER General category "Nd" in the Unicode specification.
byte DIRECTIONALITY_ARABIC_NUMBER Weak bidirectional character type "AN" in the Unicode specification.
byte DIRECTIONALITY_BOUNDARY_NEUTRAL Weak bidirectional character type "BN" in the Unicode specification.
byte DIRECTIONALITY_COMMON_NUMBER_SEPARATOR Weak bidirectional character type "CS" in the Unicode specification.
byte DIRECTIONALITY_EUROPEAN_NUMBER Weak bidirectional character type "EN" in the Unicode specification.
byte DIRECTIONALITY_EUROPEAN_NUMBER_SEPARATOR Weak bidirectional character type "ES" in the Unicode specification.
byte DIRECTIONALITY_EUROPEAN_NUMBER_TERMINATOR Weak bidirectional character type "ET" in the Unicode specification.
byte DIRECTIONALITY_LEFT_TO_RIGHT Strong bidirectional character type "L" in the Unicode specification.
byte DIRECTIONALITY_LEFT_TO_RIGHT_EMBEDDING Strong bidirectional character type "LRE" in the Unicode specification.
byte DIRECTIONALITY_LEFT_TO_RIGHT_OVERRIDE Strong bidirectional character type "LRO" in the Unicode specification.
byte DIRECTIONALITY_NONSPACING_MARK Weak bidirectional character type "NSM" in the Unicode specification.
byte DIRECTIONALITY_OTHER_NEUTRALS Neutral bidirectional character type "ON" in the Unicode specification.
byte DIRECTIONALITY_PARAGRAPH_SEPARATOR Neutral bidirectional character type "B" in the Unicode specification.
byte DIRECTIONALITY_POP_DIRECTIONAL_FORMAT Weak bidirectional character type "PDF" in the Unicode specification.
byte DIRECTIONALITY_RIGHT_TO_LEFT Strong bidirectional character type "R" in the Unicode specification.
byte DIRECTIONALITY_RIGHT_TO_LEFT_ARABIC Strong bidirectional character type "AL" in the Unicode specification.
byte DIRECTIONALITY_RIGHT_TO_LEFT_EMBEDDING Strong bidirectional character type "RLE" in the Unicode specification.
byte DIRECTIONALITY_RIGHT_TO_LEFT_OVERRIDE Strong bidirectional character type "RLO" in the Unicode specification.
byte DIRECTIONALITY_SEGMENT_SEPARATOR Neutral bidirectional character type "S" in the Unicode specification.
byte DIRECTIONALITY_UNDEFINED Undefined bidirectional character type.
byte DIRECTIONALITY_WHITESPACE Neutral bidirectional character type "WS" in the Unicode specification.
byte ENCLOSING_MARK General category "Me" in the Unicode specification.
byte END_PUNCTUATION General category "Pe" in the Unicode specification.
byte FINAL_QUOTE_PUNCTUATION General category "Pf" in the Unicode specification.
byte FORMAT General category "Cf" in the Unicode specification.
byte INITIAL_QUOTE_PUNCTUATION General category "Pi" in the Unicode specification.
byte LETTER_NUMBER General category "Nl" in the Unicode specification.
byte LINE_SEPARATOR General category "Zl" in the Unicode specification.
byte LOWERCASE_LETTER General category "Ll" in the Unicode specification.
byte MATH_SYMBOL General category "Sm" in the Unicode specification.
int MAX_CODE_POINT The maximum value of a Unicode code point, constant U+10FFFF.
char MAX_HIGH_SURROGATE The maximum value of a Unicode high-surrogate code unit in the UTF-16 encoding, constant '\uDBFF'.
char MAX_LOW_SURROGATE The maximum value of a Unicode low-surrogate code unit in the UTF-16 encoding, constant '\uDFFF'.
int MAX_RADIX The maximum radix available for conversion to and from strings.
char MAX_SURROGATE The maximum value of a Unicode surrogate code unit in the UTF-16 encoding, constant '\uDFFF'.
char MAX_VALUE The constant value of this field is the largest value of type char, '\uFFFF'.
int MIN_CODE_POINT The minimum value of a Unicode code point, constant U+0000.
char MIN_HIGH_SURROGATE The minimum value of a Unicode high-surrogate code unit in the UTF-16 encoding, constant '\uD800'.
char MIN_LOW_SURROGATE The minimum value of a Unicode low-surrogate code unit in the UTF-16 encoding, constant '\uDC00'.
int MIN_RADIX The minimum radix available for conversion to and from strings.
int MIN_SUPPLEMENTARY_CODE_POINT The minimum value of a Unicode supplementary code point, constant U+10000.
char MIN_SURROGATE The minimum value of a Unicode surrogate code unit in the UTF-16 encoding, constant '\uD800'.
char MIN_VALUE The constant value of this field is the smallest value of type char, '\u0000'.
byte MODIFIER_LETTER General category "Lm" in the Unicode specification.
byte MODIFIER_SYMBOL General category "Sk" in the Unicode specification.
byte NON_SPACING_MARK General category "Mn" in the Unicode specification.
byte OTHER_LETTER General category "Lo" in the Unicode specification.
byte OTHER_NUMBER General category "No" in the Unicode specification.
byte OTHER_PUNCTUATION General category "Po" in the Unicode specification.
byte OTHER_SYMBOL General category "So" in the Unicode specification.
byte PARAGRAPH_SEPARATOR General category "Zp" in the Unicode specification.
byte PRIVATE_USE General category "Co" in the Unicode specification.
int SIZE The number of bits used to represent a char value in unsigned binary form, constant 16.
byte SPACE_SEPARATOR General category "Zs" in the Unicode specification.
byte START_PUNCTUATION General category "Ps" in the Unicode specification.
byte SURROGATE General category "Cs" in the Unicode specification.