public static void copy(Reader input, OutputStream output)
            throws IOException {
        copy(input, output, Charset.defaultCharset());
    }
Copy chars from a <code>Reader</code> to bytes on an
<code>OutputStream</code> using the default character encoding of the
platform, and calling flush.
<p>
This method buffers the input internally, so there is no need to use a
<code>BufferedReader</code>.
<p>
Due to the implementation of OutputStreamWriter, this method performs a
flush.
<p>
This method uses {@link OutputStreamWriter}.

@param input  the <code>Reader</code> to read from
@param output the <code>OutputStream</code> to write to
@throws NullPointerException if the input or output is null
@throws IOException          if an I/O error occurs
@since 1.1
pay-java-common/src/main/java/com/egzosn/pay/common/util/IOUtils.java