Java IO.pdf - Nguyen Dang Binh

Java I/O
Chapter 14. Multilingual Character Sets and Unicode
We live on a planet on which many languages are spoken. I can walk out my front door in
Brooklyn on any given day and hear people conversing in French, Creole, Hebrew, Arabic,
Spanish, and languages I don't even recognize. And the Internet is even more diverse than
Brooklyn. A local doctor's office that sets up a storefront on the Web to sell vitamins may
soon find itself shipping to customers whose native language is Chinese, Gujarati, Turkish,
German, Portuguese, or something else. There's no such thing as a local business on the
Internet.
However, the first computers and the first programming languages were mostly designed by
English-speaking programmers in countries where English was the native language. These
programmers designed character sets that worked well for English text, though not much else.
The preeminent such set is ASCII. Since ASCII is a seven-bit character set, each ASCII
character can easily be represented as a single byte, signed or unsigned. Thus, it's natural for
ASCII-based programming languages to equate the character data type with the byte data
type. In these languages, such as C, the same operations that read and write bytes also read
and write characters.
Unfortunately, ASCII is inadequate for almost all non-English languages. It contains no
cedillas, umlauts, betas, thorns, or any of the other thousands of non-English characters that
are used to read and write text around the world. Fairly shortly after the development of
ASCII, there was an explosion of extended character sets around the world, each of which
encoded the basic ASCII characters as well as the additional characters needed for another
language like Greek, Turkish, Arabic, Chinese, Japanese, or Russian. Many of these character
sets are still used today, and much existing data is encoded in them.
However, these character sets are still inadequate for many needs. For one thing, most assume
that you only want to encode English plus one other language. This makes it difficult for a
Russian classicist to write a commentary on an ancient Greek text, for example. Furthermore,
documents are limited by their character sets. Email sent from Morocco may become illegible
in India if the sender is using an Arabic character set but the recipient is using Devanagari.
Unicode is an international effort to provide a single character set that everyone can use.
Unicode supports the characters needed for English, Arabic, Cyrillic, Greek, Devanagari, and
many others. Unicode isn't perfect. There are some omissions, especially in the ideographic
character sets for Chinese and Japanese, but it is the most comprehensive character set yet
devised for all the languages of planet Earth.
Java is one of the first programming languages to explicitly address the need for non-English
text. It does this by adopting Unicode as its native character set. All Java chars and strings are
given in Unicode. However, since there's also a lot of non-Unicode legacy text in the world,
in a dizzying array of encodings, Java also provides the classes you need to read and write
text in these encodings as well.
14.1 Unicode
Unicode is Java's native character set. Each Unicode character is a two-byte, unsigned number
with a value between and 65,535. This provides enough space for characters from all the
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