Why does "piping" a CharBuffer hang?

Question

Why does the following method hang?

public void pipe(Reader in, Writer out) {
    CharBuffer buf = CharBuffer.allocate(DEFAULT_BUFFER_SIZE);
    while( in.read(buf) >= 0 ) {
      out.append(buf.flip());
    }
}

Answer 1

Answering my own question: you have to call buf.clear() between reads. Presumably, read is hanging because the buffer is full. The correct code is

public void pipe(Reader in, Writer out) {
    CharBuffer buf = CharBuffer.allocate(DEFAULT_BUFFER_SIZE);
    while( in.read(buf) >= 0 ) {
      out.append(buf.flip());
      buf.clear();
    }
}

Answer 2

I would assume that it is a deadlock. The in.read(buf) locks the CharBuffer and prevents the out.append(buf) call.

That is assuming that CharBuffer uses locks (of some kind)in the implementation. What does the API say about the class CharBuffer?

Edit: Sorry, some kind of short circuit in my brain... I confused it with something else.