CharsetDecoder should be what you are looking for, no ?
Many network protocols and files store their characters with a byte-oriented character set such as ISO-8859-1 (ISO-Latin-1).
However, Java's native character encoding is Unicode UTF16BE (Sixteen-bit UCS Transformation Format, big-endian byte order).
See Charset. That doesn't mean UTF16 is the default charset (i.e.: the default "mapping between sequences of sixteen-bit Unicode code units and sequences of bytes"):
Every instance of the Java virtual machine has a default charset, which may or may not be one of the standard charsets.
[US-ASCII,ISO-8859-1a.k.a.ISO-LATIN-1,UTF-8,UTF-16BE,UTF-16LE,UTF-16]
The default charset is determined during virtual-machine startup and typically depends upon the locale and charset being used by the underlying operating system.
This example demonstrates how to convert ISO-8859-1 encoded bytes in a ByteBuffer to a string in a CharBuffer and visa versa.
// Create the encoder and decoder for ISO-8859-1
Charset charset = Charset.forName("ISO-8859-1");
CharsetDecoder decoder = charset.newDecoder();
CharsetEncoder encoder = charset.newEncoder();
try {
// Convert a string to ISO-LATIN-1 bytes in a ByteBuffer
// The new ByteBuffer is ready to be read.
ByteBuffer bbuf = encoder.encode(CharBuffer.wrap("a string"));
// Convert ISO-LATIN-1 bytes in a ByteBuffer to a character ByteBuffer and then to a string.
// The new ByteBuffer is ready to be read.
CharBuffer cbuf = decoder.decode(bbuf);
String s = cbuf.toString();
} catch (CharacterCodingException e) {
}