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Chapter 10 The java.lang Package |
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Chapter 10 The java.lang Package |
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java.lang.Character
java.lang.Object
None
java.io.Serializable
JDK 1.0 or later
The Character class provides an object wrapper for a char value. This is useful when you need to treat a char value as an object. For example, there are a number of utility methods that take a reference to an Object as one of their arguments. You cannot specify a char value for one of these arguments, but you can provide a reference to a Character object that encapsulates the char value. Furthermore, as of JDK 1.1, the Character class is necessary to support the Reflection API and class literals.
In Java, Character objects represent values defined by the Unicode standard. Unicode is defined by an organization called the Unicode Consortium. The defining document for Unicode is The Unicode Standard, Version 2.0 (ISBN 0-201-48345-9). More recent information about Unicode is available at http://unicode.org. Appendix a, The Unicode 2.0 Character Set, contains a table that lists the characters defined by the Unicode 2.0 standard.
The Character class provides some utility methods, such as methods for determining the type (e.g., uppercase or lowercase, digit or letter) of a character and for converting from uppercase to lowercase. The logic for these utility methods is based on a Unicode attribute table that is part of the Unicode standard. That table is available at ftp://unicode.org/pub/2.0-Update/UnicodeData-2.0.14.txt.
Some of the methods in the Character class are concerned with characters that are digits; these characters are used by a number of other classes to convert strings that contain numbers into actual numeric values. The digit-related methods all use a radix value to interpret characters. The radix is the numeric base used to represent numbers as characters or strings. Octal is a radix 8 representation, while hexadecimal is a radix 16 representation. The methods that require a radix parameter use it to determine which characters should be treated as valid digits. In radix 2, only the characters `0' and `1' are valid digits. In radix 16, the characters `0' through `9', `a' through `z', and `A' through `Z' are considerd valid digits.
public final class java.lang.Character extends java.lang.Object
implements java.io.Serializable {
// Constants
public final static byte COMBINING_SPACING_MARK; // New in 1.1
public final static byte CONNECTOR_PUNCTUATION; // New in 1.1
public final static byte CONTROL; // New in 1.1
public final static byte CURRENCY_SYMBOL; // New in 1.1
public final static byte DASH_PUNCTUATION; // New in 1.1
public final static byte DECIMAL_DIGIT_NUMBER; // New in 1.1
public final static byte ENCLOSING_MARK; // New in 1.1
public final static byte END_PUNCTUATION; // New in 1.1
public final static byte FORMAT; // New in 1.1
public final static byte LETTER_NUMBER; // New in 1.1
public final static byte LINE_SEPARATOR; // New in 1.1
public final static byte LOWERCASE_LETTER; // New in 1.1
public final static byte MATH_SYMBOL; // New in 1.1
public final static int MAX_RADIX;
public final static char MAX_VALUE;
public final static int MIN_RADIX;
public final static char MIN_VALUE;
public final static byte MODIFIER_LETTER; // New in 1.1
public final static byte MODIFIER_SYMBOL; // New in 1.1
public final static byte NON_SPACING_MARK; // New in 1.1
public final static byte OTHER_LETTER; // New in 1.1
public final static byte OTHER_NUMBER; // New in 1.1
public final static byte OTHER_PUNCTUATION; // New in 1.1
public final static byte OTHER_SYMBOL; // New in 1.1
public final static byte PARAGRAPH_SEPARATOR; // New in 1.1
public final static byte PRIVATE_USE; // New in 1.1
public final static byte SPACE_SEPARATOR; // New in 1.1
public final static byte START_PUNCTUATION; // New in 1.1
public final static byte SURROGATE; // New in 1.1
public final static byte TITLECASE_LETTER; // New in 1.1
public final static Class TYPE; // New in 1.1
public final static byte UNASSIGNED; // New in 1.1
public final static byte UPPERCASE_LETTER; // New in 1.1
// Constructors
public Character(char value);
// Class Methods
public static int digit(char ch, int radix);
public static char forDigit(int digit, int radix);
public static int getNumericValue(char ch); // New in 1.1
public static int getType(char ch); // New in 1.1
public static boolean isDefined(char ch);
public static boolean isDigit(char ch);
public static boolean isIdentifierIgnorable(char ch); // New in 1.1
public static boolean isISOControl(char ch); // New in 1.1
public static boolean isJavaIdentifierPart(char ch); // New in 1.1
public static boolean isJavaIdentifierStart(char ch); // New in 1.1
public static boolean isJavaLetter(char ch); // Deprecated in 1.1
public static boolean isJavaLetterOrDigit(char ch); // Deprecated in 1.1
public static boolean isLetter(char ch);
public static boolean isLetterOrDigit(char ch);
public static boolean isLowerCase(char ch);
public static boolean isSpace(char ch); // Deprecated in 1.1
public static boolean isSpaceChar(char ch); // New in 1.1
public static boolean isTitleCase(char ch);
public static boolean isUnicodeIdentifierPart(char ch); // New in 1.1
public static boolean isUnicodeIdentifierStart(char ch);// New in 1.1
public static boolean isUpperCase(char ch);
public static boolean isWhitespace(char ch); // New in 1.1
public static char toLowerCase(char ch);
public static char toTitleCase(char ch);
public static char toUpperCase(char ch);
// Instance Methods
public char charValue();
public boolean equals(Object obj);
public int hashCode();
public String toString();
}
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
The maximum value that can be specified for a radix.
The largest value that can be represented by a char.
The minimum value that can be specified for a radix.
The smallest value that can be represented by a char.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
The Class object that represents the type char. It is always true that Character.TYPE == char.class.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
New as of JDK 1.1
This constant can be returned by the getType() method as the general category of a Unicode character.
The char value to be encapsulated by this object.
Creates a Character object with the given char value.
A char value that is a legal digit in the given radix.
The radix used in interpreting the specified character as a digit. If radix is in the range 2 through 10, only characters for which the isDigit() method returns true are considered to be valid digits. If radix is in the range 11 through 36, characters in the ranges `A' through `Z' and `a' through `z' may be considered valid digits.
The numeric value of the digit. This method returns -1 if the value of ch is not considered a valid digit, if radix is less than MIN_RADIX, or if radix is greater than MAX_RADIX.
Returns the numeric value represented by a digit character. For example, digit('7',10) returns 7. If the value of ch is not a valid digit, the method returns -1. For example, digit('7',2) returns -1 because '7' is not a valid digit in radix 2. A number of methods in other classes use this method to convert strings that contain numbers to actual numeric values. The forDigit() method is an approximate inverse of this method.
If radix is greater than 10, characters in the range `A' to `A'+radix-11 are treated as valid digits. Such a character has the numeric value ch-`A'+10. By the same token, if radix is greater than 10, characters in the range `a' to `a'+radix-11 are treated as valid digits. Such a character has the numeric value ch-`a'+10.
The numeric value represented as a digit character.
The radix used to represent the specified value.
The character that represents the digit corresponding to the specified numeric value. The method returns `\ 0' if digit is less than 0, if digit is equal to or greater than radix, if radix is less than MIN_RADIX, or if radix is greater than MAX_RADIX.
This method returns the character that represents the digit corresponding to the specified numeric value. If digit is in the range 0 through 9, the method returns `0'+digit. If digit is in the range 10 through MAX_RADIX-1, the method returns `a'+digit-10. The method returns `\ 0' if digit is less than 0, if digit is equal to or greater than radix, if radix is less than MIN_RADIX, or if radix is greater than MAX_RADIX.
New as of JDK 1.1
A char value.
The Unicode numeric value of the character as a nonnegative integer. This method returns -1 if the character has no numeric value; it returns -2 if the character has a numeric value that is not a nonnegative integer, such as 1/2.
This method returns the Unicode numeric value of the specified character as a nonnegative integer.
New as of JDK 1.1
A char value.
An int value that represents the Unicode general category type of the character.
This method returns the Unicode general category type of the specified character. The value corresponds to one of the general category constants defined by Character.
A char value to be tested.
true if the specified character has an assigned meaning in the Unicode character set; otherwise false.
This method returns true if the specified character value has an assigned meaning in the Unicode character set.
A char value to be tested.
true if the specified character is defined as a digit in the Unicode character set; otherwise false.
This method determines whether or not the specified character is a digit, based on the definition of the character in Unicode.
New as of JDK 1.1
A char value to be tested.
true if the specified character is ignorable in a Java or Unicode identifier; otherwise false.
This method determines whether or not the specified character is ignorable in a Java or Unicode identifier. The following characters are ignorable in a Java or Unicode identifier:
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\u0000 - \u0008 \u000E - \u001B \u007F - \u009F |
ISO control characters that aren't whitespace |
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\u200C - \u200F |
Join controls |
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\u200A - \u200E |
Bidirectional controls |
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\u206A - \u206F |
Format controls |
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\uFEFF |
Zero-width no-break space |
New as of JDK 1.1
A char value to be tested.
true if the specified character is an ISO control character; otherwise false.
This method determines whether or not the specified character is an ISO control character. A character is an ISO control character if it falls in the range \u0000 through \u001F or \u007F through \u009F.
New as of JDK 1.1
A char value to be tested.
true if the specified character can appear after the first character in a Java identifier; otherwise false.
This method returns true if the specified character can appear in a Java identifier after the first character. A character is considered part of a Java identifier if and only if it is a letter, a digit, a currency symbol (e.g., $), a connecting punctuation character (e.g., _), a numeric letter (e.g., a Roman numeral), a combining mark, a nonspacing mark, or an ignorable control character.
New as of JDK 1.1
A char value to be tested.
true if the specified character can appear as the first character in a Java identifier; otherwise false.
This method returns true if the specified character can appear in a Java identifier as the first character. A character is considered a start of a Java identifier if and only if it is a letter, a currency symbol (e.g., $), or a connecting punctuation character (e.g., _).
Deprecated as of JDK 1.1
A char value to be tested.
true if the specified character can appear as the first character in a Java identifier; otherwise false.
This method returns true if the specified character can appear as the first character in a Java identifier. A character is considered a Java letter if and only if it is a letter, the character $, or the character _ . This method returns false for digits because digits are not allowed as the first character of an identifier.
This method is deprecated as of JDK 1.1. You should use isJavaIdentifierStart() instead.
Deprecated as of JDK 1.1
A char value to be tested.
true if the specified character can appear after the first character in a Java identifier; otherwise false.
This method returns true if the specified character can appear in a Java identifier after the first character. A character is considered a Java letter or digit if and only if it is a letter, a digit, the character $, or the character _.
This method is deprecated as of JDK 1.1. You should use isJavaIdentifierPart() instead.
A char value to be tested.
true if the specified character is defined as a letter in the Unicode character set; otherwise false.
This method determines whether or not the specified character is a letter, based on the definition of the character in Unicode. This method does not consider character values in ranges that have not been assigned meanings by Unicode to be letters.
A char value to be tested.
true if the specified character is defined as a letter in the Unicode character set; otherwise false.
This method determines whether or not the specified character is a letter or a digit, based on the definition of the character in Unicode. There are some ranges that have not been assigned meanings by Unicode. If a character value is in one of these ranges, this method does not consider the character to be a letter.
A char value to be tested.
true if the specified character is defined as lowercase in the Unicode character set; otherwise false.
This method determines whether or not the specified character is lowercase. Unicode defines a number of characters that do not have case mappings; if the specified character is one of these characters, the method returns false.
Deprecated as of JDK 1.1
A char value to be tested.
true if the specified character is defined as whitespace in the ISO-Latin-1 character set; otherwise false.
This method determines whether or not the specified character is whitespace. This method recognizes the whitespace characters shown in the following table.
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\u0009 |
Horizontal tab |
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\u000A |
Newline |
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\u000C |
Formfeed |
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\u000D |
Carriage return |
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\u0020 ` ` |
Space |
This method is deprecated as of JDK 1.1. You should use isWhitespace() instead.
New as of JDK 1.1
A char value to be tested.
true if the specified character is a Unicode 2.0 space characters; otherwise false.
This method determines if the specified character is a space character according to the Unicode 2.0 specification. A character is considered to be a Unicode space character if and only if it has the general category "Zs", "Zl", or "Zp" in the Unicode specification.
A char value to be tested.
true if the specified character is defined as titlecase in the Unicode character set; otherwise false.
This method determines whether or not the specified character is a titlecase character. Unicode defines a number of characters that do not have case mappings; if the specified character is one of these characters, the method returns false.
Many characters are defined by the Unicode standard as having upper- and lowercase forms. There are some characters defined by the Unicode standard that also have a titlecase form. The glyphs for these characters look like a combination of two Latin letters. The titlecase form of these characters has a glyph that looks like a combination of an uppercase Latin character and a lowercase Latin character; this case should be used when the character appears as the first character of a word in a title. For example, one of the Unicode characters that has a titlecase form looks like the letter `D' followed by the letter `Z'. Here is what the three forms of this letter look like:
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Uppercase |
`DZ' |
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Titlecase |
`Dz' |
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Lowercase |
`dz' |
New as of JDK 1.1
A char value to be tested.
true if the specified character can appear after the first character in a Unicode identifier; otherwise false.
This method returns true if the specified character can appear in a Unicode identifier after the first character. A character is considered part of a Unicode identifier if and only if it is a letter, a digit, a connecting punctuation character (e.g., _), a numeric letter (e.g., a Roman numeral), a combining mark, a nonspacing mark, or an ignorable control character.
New as of JDK 1.1
A char value to be tested.
true if the specified character can appear as the first character in a Unicode identifier; otherwise false.
This method returns true if the specified character can appear in a Unicode identifier as the first character. A character is considered a start of a Unicode identifier if and only if it is a letter.
A char value to be tested.
true if the specified character is defined as uppercase in the Unicode character set; otherwise false.
This method determines whether or not the specified character is uppercase. Unicode defines a number of characters that do not have case mappings; if the specified character is one of these characters, the method returns false.
New as of JDK 1.1
A char value to be tested.
true if the specified character is defined as whitespace according to Java; otherwise false.
This method determines whether or not the specified character is whitespace. This method recognizes the following as whitespace:
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Unicode category "Zs" except \u00A0 and \uFEFF |
Unicode space separators except no-break spaces |
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Unicode category "Zl" |
Unicode line separators |
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Unicode category "Zp" |
Unicode paragraph separators |
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\u0009 |
Horizontal tab |
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\u000A |
Linefeed |
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\u000B |
Vertical tab |
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\u000C |
Formfeed |
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\u000D |
Carriage return |
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\u001C |
File separator |
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\u001D |
Group separator |
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\u001E |
Record separator |
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\u001F |
Unit separator |
A char value to be converted to lowercase.
The lowercase equivalent of the specified character, or the character itself if it cannot be converted to lowercase.
This method returns the lowercase equivalent of the specified character value. If the specified character is not uppercase or if it has no lowercase equivalent, the character is returned unmodified. The Unicode attribute table determines if a character has a mapping to a lowercase equivalent.
Some Unicode characters in the range \u2000 through \u2FFF have lowercase mappings. For example, \u2160 (Roman numeral one) has a lowercase mapping to \u2170 (small Roman numeral one). The toLowerCase() method maps such characters to their lowercase equivalents even though the method isUpperCase() does not return true for such characters.
A char value to be converted to titlecase.
The titlecase equivalent of the specified character, or the character itself if it cannot be converted to titlecase.
This method returns the titlecase equivalent of the specified character value. If the specified character has no titlecase equivalent, the character is returned unmodified. The Unicode attribute table is used to determine the character's titlecase equivalent.
Many characters are defined by the Unicode standard as having upper- and lowercase forms. There are some characters defined by the Unicode standard that also have a titlecase form. The glyphs for these characters look like a combination of two Latin letters. The titlecase form of these characters has a glyph that looks like a combination of an uppercase Latin character and a lowercase Latin character; this case should be used when the character appears as the first character of a word in a title. For example, one of the Unicode characters that has a titlecase form looks like the letter `D' followed by the letter `Z'. Here is what the three forms of this letter look like:
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Uppercase |
`DZ' |
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Titlecase |
`Dz' |
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Lowercase |
`dz' |
A char value to be converted to lowercase.
The uppercase equivalent of the specified character, or the character itself if it cannot be converted to uppercase.
This method returns the uppercase equivalent of the specified character value. If the specified character is not lowercase or if it has no uppercase equivalent, the character is returned unmodified. The Unicode attribute table determines if a character has a mapping to an uppercase equivalent.
Some Unicode characters in the range \u2000 through \u2FFF have uppercase mappings. For example, \u2170 (small Roman numeral one) has a lowercase mapping to \u2160 (Roman numeral one). The toUpperCase() method maps such characters to their uppercase equivalents even though the method isLowerCase() does not return true for such characters.
The char value contained by the object.
The object to be compared with this object.
true if the objects are equal; false if they are not.
Object.equals()
This method returns true if obj is an instance of Character, and it contains the same value as the object this method is associated with.
A hashcode based on the char value of the object.
Object.hashCode()
A String of length one that contains the character value of the object.
Object.toString()
This method returns a string representation of the Character object.
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Method |
Inherited From |
Method |
Inherited From |
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clone() |
Object |
finalize() |
Object |
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getClass() |
Object |
notify() |
Object |
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notifyAll() |
Object |
wait() |
Object |
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wait(long) |
Object |
wait(long, int) |
Object |
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| Byte |  |
Class |
