Char

The {@code Character} class wraps a value of the primitive type {@code char} in an object. An object of type {@code Character} contains a single field whose type is {@code 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 8.0.0. The methods and data of class {@code 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: <ul> <li><a href="http://www.unicode.org">http://www.unicode.org</a> </ul>

<h3><a id="unicode">Unicode Character Representations</a></h3>

The {@code char} data type (and therefore the value that a {@code 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 <a href="http://www.unicode.org/reports/tr27/#notation"> definition</a> of the U+n notation in the Unicode Standard.)

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

A {@code char} value, therefore, represents Basic Multilingual Plane (BMP) code points, including the surrogate code points, or code units of the UTF-16 encoding. An {@code int} value represents all Unicode code points, including supplementary code points. The lower (least significant) 21 bits of {@code 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 {@code char} values is as follows:

<ul> <li>The methods that only accept a {@code char} value cannot support supplementary characters. They treat {@code char} values from the surrogate ranges as undefined characters. For example, {@code Character.isLetter('\u005CuD840')} returns {@code false}, even though this specific value if followed by any low-surrogate value in a string would represent a letter.

<li>The methods that accept an {@code int} value support all Unicode characters, including supplementary characters. For example, {@code Character.isLetter(0x2F81A)} returns {@code true} because the code point value represents a letter (a CJK ideograph). </ul>

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 {@code char} values that are code units of the UTF-16 encoding. For more information on Unicode terminology, refer to the <a href="http://www.unicode.org/glossary/">Unicode Glossary</a>.

Char

Constructors

Members

Functions

Static functions

Variables

Meta

Source