A charset coder, that is, either a decoder or an encoder, consumes bytes (or characters) from an input buffer, translates them, and writes the resulting characters (or bytes) to an output buffer. A coding process terminates for one of four categories of reasons, which are described by instances of this class:

• Underflow is reported when there is no more input to be processed, or there is insufficient input and additional input is required. This condition is represented by the unique result object CoderResult.UNDERFLOW, whose isUnderflow method returns true.

• Overflow is reported when there is insufficient room remaining in the output buffer. This condition is represented by the unique result object CoderResult.OVERFLOW, whose isOverflow method returns true.

• A malformed-input error is reported when a sequence of input units is not well-formed. Such errors are described by instances of this class whose isMalformed method returns true and whose length method returns the length of the malformed sequence. There is one unique instance of this class for all malformed-input errors of a given length.

• An unmappable-character error is reported when a sequence of input units denotes a character that cannot be represented in the output charset. Such errors are described by instances of this class whose isUnmappable method returns true and whose length method returns the length of the input sequence denoting the unmappable character. There is one unique instance of this class for all unmappable-character errors of a given length.