Char equivalent of UnsynchronizedByteArrayOutputStream (and InputStream)

I was thinking of writing this and submitting it but just want to see if people think it makes sense first.

The idea is to take AbstractByteArrayOutputStream and to replace the byte[] with char[] (maybe called AbstractCharArrayWriter) and to create an UnsynchronizedCharArrayWriter that extends it. Could so something similar with UnsynchronizedByteArrayInputStream - to get an UnsynchronizedStringReader.

The nice thing about AbstractByteArrayOutputStream is the way it avoids arraycopy. The existing commons-io StringBuilderWriter still has arraycopy under the hood (in the java.lang.StringBuilder).