Java IO.pdf - Nguyen Dang Binh

Java I/O
world's alphabetic scripts and the most common characters from the ideographic scripts of
Chinese and Japanese. The current version of Unicode (2.1) defines 38,887 different
characters from many languages, including English, Russian, Arabic, Hebrew, Greek, Thai,
Korean, and Sanskrit. The most common ideographic characters from Japanese and Chinese
are also included. However, Chinese alone contains over 80,000 different ideograms, so it's
impossible to include them all in a two-byte set. A four-byte Universal Character Set (UCS)
that will include the full Chinese and Japanese scripts is under development. Java does not yet
support UCS.
The first 128 Unicode characters (characters through 127) are identical to the ASCII character
set. 32 is the ASCII space; therefore, 32 is the Unicode space. 33 is the ASCII exclamation
point, so 33 is the Unicode exclamation point, and so on. Table B.1, in Appendix B, shows
this character set. The next 128 Unicode characters (characters 128 through 255) have the
same values as the equivalent characters in the Latin-1 character set defined by ISO standard
8859-1. Latin-1, a slight variation of which is used by Windows, adds the various accented
characters, umlauts, cedillas, upside-down question marks, and other characters needed to
write text in most Western European languages. Table B.2 shows these characters. The first
128 characters in Latin-1 are identical to the ASCII character set.
Values beyond 255 encode characters from various other character sets. Where possible,
character blocks describing a particular group of characters map onto established encodings
for that set of characters by simple transposition. For instance, Unicode characters 884
through 1011 encode the Greek alphabet and associated characters like the Greek question
mark (;). [1] This is a direct transposition by 756 of characters 128 through 255 of the ISO
8859-7 character set, which is in turn based on the Greek national standard ELOT 928. For
example, the small letter delta, , ISO 8859-7 character 228, is Unicode character 984. A
small epsilon, , ISO 8859-7 character 229, is Unicode character 985. In general, the
Unicode value for a Greek character equals the ISO 8859-7 value for the character plus 756.
Other character sets are included in Unicode in a similar fashion whenever possible. [2]
NextStep, BeOS, MacOS X Server, Bell Labs' Plan 9, and Windows NT 4.0 all support
Unicode to some extent. Unicode support in MacOS and Windows 98 is more nascent, but it's
coming. Application software is a little slower to appear, but Microsoft Word 97 and 98,
Netscape Navigator 4.0, and Internet Explorer 4.0 all support Unicode. The big hold-up on
most systems is fonts and input methods. Windows NT 5.0 will include fonts covering most
of the defined Unicode characters as well as input methods for most major languages.
14.2 Displaying Unicode Text
Although internally Java can handle full Unicode data (it's just numbers, after all), not all Java
environments can display all Unicode characters. In fact, I'll go so far as to say none of the
current Java environments, whether standalone virtual machines or web browsers, can display
all Unicode characters.
Unicode is divided into blocks. For example, characters through 127 are the Basic Latin block
and contain ASCII. Characters 128 through 255 are the Latin Extended-A block and contain
1 Indeed, the Greek question mark is nearly identical to a Latin semicolon; this is not a mistranslation of the character.
2 As much as I'd like to include complete tables for all Unicode characters, if I did so, this book would be little more than that table. For complete lists
of all the Unicode characters and associated glyphs, the canonical reference is The Unicode Standard, Version 2.0, by the Unicode Consortium, ISBN
0-201-48345-9. Online versions of the character tables can be found at http://unicode.org/charts/.
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