Java IO.pdf - Nguyen Dang Binh

Java I/O
tie, and a few similar characters that may be included in the interior of a Unicode identifier
but may not start it.
The isJavaIdentifierStart() method returns true if the specified character is a valid
beginning of an identifier in Java source code; that is, if it's a letter as determined by
isLetter(), or if it's a currency indicator like $ or £, or if it's a connecting punctuation
character like the underscore (_).
public static boolean isJavaIdentifierStart(char c)
This method might be used by Java compilers and similar tools.
The isJavaIdentifierPart() method is similar but also returns true if the specified
character is a digit in any of Unicode's supported scripts. Digits are legal parts of Java
identifiers but may not begin an identifier.
public static boolean isJavaIdentifierPart(char c)
Numeric letters like Roman numerals, combining marks, nonspacing marks, and ignorable
control characters are also allowed in Java identifiers as long as they aren't the first characters
of the identifier. isJavaIdentifierStart() and isJavaIdentifierPart() are new in Java
1.1. Java 1.0 had identical methods, now deprecated, called isJavaLetter() and
isJavaLetterOrDigit():
public static boolean isJavaLetter(char c)
public static boolean isJavaLetterOrDigit(char c)
Certain Unicode characters are classified as ignorable within the context of Unicode and Java
identifiers. The name is something of a misnomer, since these characters aren't ignored. A
better name would be "illegal," since they can't be used in Java or Unicode identifiers.
Nonetheless, the word is ignorable; and the isIdentifierIgnorable() method returns true
if the character is ignorable:
public static boolean isIdentifierIgnorable(char c)
Ignorable characters include the nonwhitespace ASCII control characters through 8 and 14
through 27; the Latin-1 control characters 127 through 159; the joining characters 8024
through 8027; the bidirectional controls 8202 through 8206; the format controls 8298 through
8303; and the zero-width nonbreaking space 65,279.
14.5.1.5 Numeric values
java.lang.Character also has several methods for interpreting characters as numbers. The
digit() method returns the numeric value of the character c in the specified base:
public static int digit(char c, int base)
For example, Character.digit('A', 16) returns 10, because in hexadecimal (base 16) the
letter A is used as a digit with the value 10. This method handles bases between 2 and 36.
(The latter is 10 plus the 26 letters in the Roman alphabet.) These limits are available in the
mnemonic constants Character.MIN_RADIX and Character.MAX_RADIX respectively:
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