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Java's stream classes are good for streaming sequences of bytes, but they are not good for streaming sequences of characters because bytes and characters are two different things: a byte represents an 8-bit data item and a character represents a 16-bit data item. Also, Java's char and String types naturally handle characters instead of bytes.

More importantly, byte streams have no knowledge of character sets (sets of mappings between integer values [known as code points] and symbols, such as Unicode) and their character encodings (mappings between the members of a character set and sequences of bytes that encode these characters for efficiency, such as UTF-8).

If you need to stream characters, you should take advantage of Java's writer and reader classes, which were designed to support character I/O (they work with char instead of byte). Furthermore, the writer and reader classes take character encodings into account.


Early computers and programming languages were created mainly by English-speaking programmers in countries where English was the native language. They developed a standard mapping between code points 0 through 127 and the 128 commonly used characters in the English language (such as A-Z). The resulting character set/encoding was named American Standard Code for Information Interchange (ASCII).

The problem with ASCII is that it is inadequate for most non-English languages. For example, ASCII does not support diacritical marks such as the cedilla used in the French language. Because a byte can represent a maximum of 256 different characters, developers around the world started creating different character sets/encodings that encoded the 128 ASCII characters, but also encoded extra characters to meet the needs of languages such as French, Greek, or Russian. Over the years, many legacy (and still important) files have been created whose bytes represent characters defined by specific character sets/encodings.

The International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) have worked to standardize these eight-bit character sets/encodings under a joint umbrella standard called ISO/IEC 8859. The result is a series of substandards named ISO/IEC 8859-1, ISO/IEC 8859-2, and so on. For example, ISO/IEC 8859-1 (also known as Latin-1) defines a character set/encoding that consists of ASCII plus the characters covering most Western European countries. Also, ISO/IEC 8859-2 (also known as Latin-2) defines a similar character set/encoding covering Central and Eastern European countries.

Despite ISO's/IEC's best efforts, a plethora of character sets/encodings is still inadequate. For example, most character sets/encodings only allow you to create documents in a combination of English and one other language (or a small number of other languages). You cannot, for example, use an ISO/IEC character set/encoding to create a document using a combination of English, French, Turkish, Russian, and Greek characters.

This and other problems are being addressed by an international effort that has created and is continuing to develop Unicode, a single universal character set. Because Unicode characters are twice as big as ISO/IEC characters, Unicode uses one of several variable-length encoding schemes known as Unicode Transformation Format (UTF) to encode Unicode characters for efficiency. For example, UTF-8 encodes every character in the Unicode character set in one to four bytes (and is backward compatible with ASCII).

The terms character set and character encoding are often used interchangeably. They mean the same thing in the context of ISO/IEC character sets, where a code point is the encoding. However, these terms are different in the context of Unicode, where Unicode is the character set and UTF-8 is one of several possible character encodings for Unicode characters.

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