code: public static long copy(ReadableByteChannel inputChannel, WritableByteChannel outputChannel) throws IOException {
      return new StreamCopier(inputChannel, outputChannel).copy();
    }
docs: Copies a {@link ReadableByteChannel} to a {@link WritableByteChannel}.
  <p>
  <b>Note:</b> The {@link ReadableByteChannel} and {@link WritableByteChannel}s are NOT closed by the method
  </p>
  
  @return Total bytes copied