JDK-8191706: Proposal to add Reader::transferTo(Writer)

[Patrick Reinhart]

Hi there out a the review [1] for  JDK-8066870, that will need some more
working on, I created this specific issue to add an transferTo method to
the java.io.Reader as it seems more clear as of the similarity to
java.io.InputStream.transferTo(java.io.OutputStream) in terms of the API.

To start the discussion I got the proposed API:

/**
 * Reads all characters from this reader and writes the characters to the
 * given writer in the order that they are read. On return, this reader
 * will be at end of the data. This method does not close either reader
 * or writer.
 * <p>
 * This method may block indefinitely reading from the reader, or
 * writing to the writer. The behavior for the case where the reader
 * and/or writer is <i>asynchronously closed</i>, or the thread
 * interrupted during the transfer, is highly reader and writer
 * specific, and therefore not specified.
 * <p>
 * If an I/O error occurs reading from the reader or writing to the
 * writer, then it may do so after some characters have been read or
 * written. Consequently the reader may not be at end of the data and
 * one, or both, streams may be in an inconsistent state. It is strongly
 * recommended that both streams be promptly closed if an I/O error occurs.
 *
 * @param  out the writer, non-null
 * @return the number of characters transferred
 * @throws IOException if an I/O error occurs when reading or writing
 * @throws NullPointerException if {@code out} is {@code null}
 *
 * @since 10
 */
public long transferTo(Writer out) throws IOException {
....
}


-Patrick


[1]
http://mail.openjdk.java.net/pipermail/core-libs-dev/2017-November/050064.html