JDK-8196298: Add null Reader and Writer

[Patrick Reinhart]

Hi there,

I saw that great extension on InputStream/OutputStream adding a Null
implementation there. Based on those I would propose a similar addition
to the Reader/Writer.

-Patrick


Here is what the API would look like based on the existing from
InputStream/OutputStream:


    /**
     * Returns a new {@code Reader} that contains no characters. The
returned
     * stream is initially open.  The stream is closed by calling the
     * {@code close()} method.  Subsequent calls to {@code close()} have no
     * effect.
     *
     * <p> While the stream is open, the {@code ready​()}, {@code read()},
     * {@code read(char[])}, {@code read(char[], int, int)}, {@code
skip()}, and
     * {@code transferTo()} methods all behave as if end of stream has been
     * reached.  After the stream has been closed, these methods all throw
     * {@code IOException}.
     *
     * <p> The {@code markSupported()} method returns {@code false}.  The
     * {@code mark()} method does nothing, and the {@code reset()} method
     * throws {@code IOException}.
     *
     * @return an {@code Reader} which contains no characters
     *
     * @since 11
     */
    public static Reader nullReader() {}


    /**
     * Returns a new {@code Writer} which discards all characters.  The
     * returned stream is initially open.  The stream is closed by calling
     * the {@code close()} method.  Subsequent calls to {@code close()} have
     * no effect.
     *
     * <p> While the stream is open, the {@code write(int)}, {@code
     * write(char[])}, and {@code write(char[], int, int)} methods do
nothing.
     * After the stream has been closed, these methods all throw {@code
     * IOException}.
     *
     * <p> The {@code flush()} method does nothing.
     *
     * @return an {@code Writer} which discards all characters
     *
     * @since 11
     */
    public static Writer nullWriter() {}