Acharset is named mapping between sequences of sixteen-bit Unicode characters and sequences of bytes, in the sense defined inRFC 2278. Adecoder is an engine which transforms bytes in a specific charset into characters, and anencoder is an engine which transforms characters into bytes. Encoders and decoders operate on byte and character buffers. They are collectively referred to ascoders.

TheCharset class defines methods for creating coders for a given charset and for retrieving the various names associated with a charset. It also defines static methods for testing whether a particular charset is supported, for locating charset instances by name, and for constructing a map that contains every charset for which support is available in the current Java virtual machine.

Most users will not use these classes directly; instead they will use the existing charset-related constructors and methods in theString class, together with the existingInputStreamReader andOutputStreamWriter classes, all of whose implementations have been reworked to make use of the charset facilities defined in this package. A small number of changes have been made to theInputStreamReader andOutputStreamWriter classes in order to allow explicit charset objects to be specified in the construction of instances of those classes.

Support for new charsets can be made available via the interface defined in theCharsetProvider class in thejava.nio.charset.spi package.

Unless otherwise noted, passing anull argument to a constructor or method in any class or interface in this package will cause aNullPointerException to be thrown.